The girl who owned the car was enrolled in one of the other programs at the college, which qualified her to have the work done in my department.
When I sat down in the car and started it, there were noises coming from everywhere. The car was a tow-truck ride away from the boneyard; there was more wrong with it that there was right. Although it did start and it could be driven down the highway, the front and rear engine mounts were both separated, and the powertrain was trying to jump out of the car every time we put it in either forward or reverse. The engine seemed noisy, too, but our initial focus was on the transmission noise she was complaining about. And there was a very peculiar popping sound that came from the transmission in reverse. It had the frequency of something dragging against the park pawl wheel, so I fruitlessly adjusted the gear selector linkage just in case the park pawl lever was somehow dragging. It was time to snatch the transmission oil pan for a look.
The bouncing ball
What we found in the pan was extremely interesting: The four large balls from one of the final drive bearings were rolling around in the pan, and one of them had managed to get trapped under the park pawl wheel, which whirls near the oil pan on this transmission. The valve body is on top of the unit under another pan.
The ball had machined itself a nice dimple in the metal of the oil pan. When the differential was turning in the reverse direction, the ball would bounce against the park pawl wheel teeth and ‘oil can’ the transmission pan, which turned out to be the source of our noise. In the forward direction, the pawl would simply move the ball to the back of its dimple and it produced no noise in that direction.
Rather than attempting an overhaul with a group of students who had no prior transmission experience, my choice was to sell the student on a good salvage yard transmission, a rear main engine oil seal and some new engine mounts. She agreed, and we found a good one for $400.
Making the swap
I always liked these ATX transmissions. When I worked at the Ford dealership, the ATX Ford that was used in Tempos and Escorts seemed to be a lot more cooperative than some of the other units I was building. In those days, we were doing a lot of A4LD work, and I never liked that particular unit. There were zillions of valves in the valve body, and they were all aluminum. We didn’t throw a lot of replacement valve bodies around in those days and diligently cleaning a really nasty A4LD valve body could take a whole day.
All in all, swapping this Tempo ATX went fairly well, even though the transmission was four years older than the car. One problem we ran into as a result of the model year difference was that the ’90 model inboard CV joints were a different spline size on both ends. The ’94 halfshafts wouldn’t fit into the ’90 model transaxle, so I had to call the wrecking yard to send us the axle shafts to go with the ’90 model unit.
Smooth shifting, knocking engine
The replacement transaxle worked flawlessly, but with all the other noises out of the way, we were hearing an engine knock. The student’s bill was already climbing to an alarming figure, but we couldn’t let that engine knock pass.
Checking the oil pressure, we found that it was a bit low, but not to the point that it should have been causing the engine knock. It was more likely that the knock was the cause of the slightly low pressure.
A couple of the students yanked the engine oil pan, and we did an inspection. The main bearings looked fine, but rods number one and two had hammered their bearings out a little thin. Finding the specs and applying the micrometer to the surprisingly smooth crankshaft journals, we found a crankshaft that was actually within specifications.
We installed a new set of rod bearings, plasti-gauged them to find nice healthy numbers. When we reinstalled the oil pan and fired it up, the oil pressure was a nice pleasing 50 psi at hot idle. We had repaired her engine knock for a mere $65. The car ran and drove very well when we were finished, and her bill had climbed to just over $700.
She paid her bill at the front office and drove away on a quiet, smooth-running little machine that must have felt like a totally different car. I was satisfied that we had done her a good job that would last her through college and into her new career. A few days later, one of my guys saw her climbing in her car at the student center and asked her how she liked the job we did on it.
“I liked it better the way it was before,” she told him. She fired up the smooth-running car and drove away.
To put it mildly, this was a confusing remark on her part, because we had seen her driving the car a few times and from the sound of it, everything was still as it should have been.
“What’ll it take to satisfy her?” he wanted to know.
I had no idea, but there’s one thing I’ve known for years. No matter what we do or how well we do it, we simply can’t control what a person likes or dislikes. That’s just one of the breaks.
Every vehicle needs its own bank account for regular maintenance, with enough “wiggle room” for unscheduled maintenance.
I taught this principle at a ladies’ car care seminar once and most of them were startled at how much you have to spend on a vehicle just to keep it properly maintained… but in the world of vehicles, “An ounce of prevention is worth a pound of cure.” is a proven strategy.
One of the most comical things I’ve heard some people say is that they don’t think they need an oil change because the car still runs good. And those people are totally oblivious to the coolant that carries away engine heat.
Then there are some people care a lot about their cars but know very little about where things are under the hood, even if they do care deeply about what goes on under there. I knew of one young woman who saw a coolant level warning light on her Jeep Liberty and was concerned enough about it that she opened her hood, got her water hose, and filled the crankcase with water.
Another customer recently came to me with her Buick smoking and making strange noises. She said she had seen the oil light come on and so she added oil, but she wasn’t sure she had added enough. I pulled the dipstick and we found that it was about five quarts overfull. When I asked her why it had so much oil in it, she said she didn’t know anything about the dipstick – she just figured she needed to add oil until she could see through the filler cap hole that it was full.
But there are some drivers who are car-conscious enough to check and change the oil regularly, and they’ll even check the rest of their fluids, but too many don’t ever think of replacing the coolant or doing anything else to the cooling system until it springs a leak or an overheating episode happens. Oil changes happen regularly. Coolant changes every sixty thousand miles tend to be forgotten. It’s sort of like the transmission – some folks don’t consider doing anything to it until it starts giving problems. And a neglected cooling system tends to develop a few problems that can’t be easily dealt with, and some of the fallout from such lassitude is more or less permanent. Flakes of rust shred water pump seals, heater cores, and radiator fins, and used-up coolant stops protecting the metal parts. I’ve repaired overheating problems in some cases by just replacing old coolant.
From our side of the service aisle, it’s a foregone that cooling system service makes a LOT of difference, and it’s a great (and necessary upsell) on vehicles that are in need. Checking the vehicle’s maintenance record and schedule is a legitimate practice too (if there is one). If you follow the manufacturer recommendations at the intervals they publish, it pays off in the long run for the customer as well as the shop. It’s a win-win, but you must sell it!
Plastic Parts That Fail
To save weight, car manufacturers have been making lots things out of plastic for decades now, and many of these plastic parts carry hot coolant, which, in many cases has been a tremendous repair boon for those of us who wrench for a living. How many shops could fill the back of a pickup with plastic coolant-carrying parts we’ve replaced over the past six months?
Awhile back, a lady came to me with a high mileage Honda Accord and asked what I would do to reduce the likelihood of mileage-related unscheduled maintenance. One of the several things I suggested to her was that we replace the radiator and the coolant along with it. Why? Well, most of us have seen more than a few engines destroyed because of an old radiator that cracked on the highway, dumped the coolant, and led to a meltdown. Then there are those radiators that leak from the rubber seal between the core and the tanks. That happens even on lower mileage platforms, and sometimes it happens with replacement radiators if they’re cheapies.
And there are those crummy plastic elbows GM used to pipe coolant through the belt tensioner on turn-of-the century 3.8L platforms, but good metal replacements are now available for those. And there are also the plastic intake manifolds that like to split and plastic-and-silicone manifold gaskets that die every day and start dumping coolant everywhere. Most of us have also replaced leaking plastic thermostat housings on Ford Explorers and those annoying plastic 2.7L water outlets (the one that comes with the ECT sensor in it).
If you put a heater core in a mid-2000s Nissan Pathfinder, you may find that under hood heater hose manifold and pipe assembly brittle to the point of dreadful fragility, and since it includes an electric water pump, it’s about 250 bucks.
The point is that there’s nothing wrong with upselling items like this to protect a customer from catastrophic breakdowns. Again, changing failure-prone plastic parts on familiar platforms that are high mileage helps protect the customer from later loss. Simply servicing the cooling system might not totally prevent plastic part failures, so on a failure prone part that doesn’t cost a lot and isn’t hard to change, selling one is a good idea, even if it’s the plastic intake manifold on a Lincoln or a Crown Victoria. Those like to leak in various places as well. But be careful to buy good parts. We’ve had to replace radiators a second time because the first replacement part started leaking at the tank/core joints after only a few thousand miles.
We replaced one plastic radiator on a 2005 Caravan (it seems like we work on a lot of those) that wound up with a percolating coolant issue after we replaced the radiator, and it turned out that the neck of the radiator was built just a bit out of spec – even with the right radiator cap installed there was almost no spring tension applied, and so the coolant wasn’t under pressure, and it would be boiling whenever she stopped the vehicle. You could remove the cap with a thumb and a forefinger. The radiator cap’s bottom seal didn’t even have a signature mark where it had been pressed against that inside lip. Experimentally, I took another new cap I had, removed the gasket, and worked it onto the new radiator cap, stacking the gaskets to apply more pressure, and the percolation stopped. The radiator still had to be replaced with another one.
The Cap Debate
Certainly one of the more interesting issues I’ve run into more than once over the past several years is in regard to brand new radiator caps with dangly vent valves. If I pull a radiator cap off an older system and see a dangling vent valve, I’m replacing it. But when the new Stant cap comes with a dangly valve, I get sort of bothered, and I make the parts guy find one with the same part number that has a tight vent valve. And he always can, it seems. When he combs his inventory, some of the same part number caps will have dangly valves and some won’t. That in and of itself is troubling, but Stant calls these danglies “partial pressure” caps.
In a “partial pressure” cap, the vent valve is free-hanging by design – there is no spring to close it, just a small weight to make it dangle. It is supposed to close only when system pressure rises high enough to cause coolant flow volume that can overcome the weight of the valve and push it shut. Thus, in these systems, the cooling system isn’t pressurized until it gets hot enough to put sudden pressure on the cap. At that point, the sudden pressure/flow that hits the cap is supposed to push the vent valve closed and then pressure increases in the cooling system. Why do this? Well, they say the system doesn’t need to be under pressure until it becomes necessary to raise the boiling point of the coolant. Supposedly, this is easier on the solder joints and other “weaker” places where building pressure can cause leaks, and I’m not a college-trained engineer, but my question would be that if those joints can’t take the pressure early on, will they even be able to handle the pressure after it rises? This is a peculiar strategy to me.
This debate may not be worth having, but I don’t like replacing one dangly vented cap with another one, if you know what I mean. Caps are cheap, though, and replacing the cap is typically a good idea.
Most of today’s cooling surge-tank type systems don’t have that kind of radiator cap anyway, but there are multiplied thousands of vehicles on the road that do.
Much Ado About Coolant
With all due respect, we’ve seen more problems with Dex-Cool than any other coolant. That orange liquid loves to turn to orange mud on systems that haven’t been serviced according to the book, and it’s very difficult to get that junk out of a system once it’s there. We’ve used all manner of methods (including “CLR”) to try and get rid of that stuff, but it usually takes repeated services over time to make it happen.
We worked on one 2006 Impala that, when you removed the filler cap, had what looked like modeling clay clogging the filler neck. We flushed and flushed that one and eventually replaced the radiator before we finally got it clean enough to be trouble-free. Green coolant went back in, and we finally got just about all of that stuff out, but periodically some of it will break loose and make an appearance when we’re servicing that one.
On my personal vehicles, I follow the maintenance guide on everything from oil changes to coolant exchanges. I have a 2007 Taurus and a 2007 F150, both of which use Motorcraft Gold, and when I replaced it in both vehicles at the required interval, the coolant I was pushing out looked as good as what I was putting in. Personally, I like the Motorcraft gold coolant best of all, but Ford has moved on to other formulas and colors now.
We presently use a Robinair coolant exchanger that works well, and before I exchange the coolant on a nasty one I like to push about fifteen quarts of water through before shoving the coolant in, but it works best when you remove the thermostat instead of letting the pressure push it open, and replace the ‘stat when you’re done.
A P0128 code basically means the engine is running a bit cooler than the PCM is programmed to accept. The P0125 code usually means a thermostat is needed, but on some Toyota platforms it can mean the O2 sensor heater isn’t working and closed loop isn’t happening soon enough or at all, and you may not get an O2 heater code. If you’re working on a Camry that seems to be running warm enough but still throws a P0125, look at the O2 heater. The problem is that some new thermostats open too soon. I sometimes had to replace one two or three times when I was at the Ford dealer to get one that would get warm enough.
It’s a no-brainer that old coolant needs to be captured during service and stored for disposal – we have a Safety Kleen bumblebee out behind the shop where we dump our tired old coolant and they come around to pump it out when they take our used engine oil and our drum of used oil filters.
Without doing a lot of internet research, I’ll say that, in my experience, that mix-with-anything coolant the parts stores sell has worked well for us in most cases, but I may get my ears combed down with emails for saying that. If the system is clean and regularly serviced, coolant is coolant, for the most part, in my opinion. There are exceptions. I try to get the right coolant for those exotic Asian and European cars whenever I can.
Using distilled water is optimum when doing the 50/50 mix thing; sometimes tap water will create problems, but most shops use it anyway with few issues.
Hoses and Stuff
Anywhere there has been oil seepage that attacks a rubber coolant hose, those hoses tend to get soft, flabby, and unreliable. And don’t we all love those OEM spring clamps that can be so annoying, especially when one of the ears snaps off on one that feeds the heater core and those connections are ‘way down there almost out of reach? Be careful of hoses that are dissolving from the inside out, because they’ll look good right up until they spring a pinhole leak. You can usually squeeze the hoses with a practiced hand and catch this early, though.
Speaking of heater core connections, be careful of replacement plastic quick-connects that don’t fit right – sometimes they’re too tight to fit properly on the heater core pipes, and on some late 90s-early 00s F150s they’re totally out of sight under the cowl when you shove them on there, so you can’t tell if the plastic retainer has passed the pipe rib or not. You might think they’re on all the way because you can’t pull them back off, but that’s because they’re a tiny bit too small to fit right. And then when the engine gets warm they inevitably blow off in those cases, and that’s bad news. If you can’t get a good replacement quick-connect in short order and the customer is waiting, it might be a good idea to dump the plastic quick connect, shove the rubber hose past that lock lip and put a screw clamp on there.
Unserviced cooling systems (or systems that have been filled for awhile with nothing but water) may have cavitated water pump reaction services and partially dissolved impellers, so if you know the cooling system is full and you don’t have good heat, check for good flow. If the impeller is plastic with an aluminum hub, sometimes those get loose on the shaft and cause similar issues. To check for flow, we pull the hoses off the heater core and put a clear hose from the local hardware store between the inlet and outlet heater core hoses to see what’s going on. It’s a neat way to find bad water pumps and clogged passages, because you can watch the flow happen. You can connect a water hose to the heater core and check for flow through as well while you’re at it.
Pressure testing is a good thing to do, but you need a really good pressure tester, and I despise those that have the stupid one-size-fitz-all rubber cone, because they tend to blow out and make a mess. I want a set that has a cap to fit most every system.
Bleeding the cooling system is an all-important task – always turn on the heater – if it was working before but it isn’t working after the fill, you may need to do extraordinary things to get the air out. On a 2005 Pathfinder we just finished, (heater core, heater pipe manifold, etc.), we had to jack the front of it up at a very steep angle and add coolant to get all the air out. Initially, one of these will seem full and won’t usually be overheating, but we had no cabin heat until we raised the front of it and poured in another half-gallon of coolant. Watch for that. Nissan Quest is similar – raise it up in the front, put a funnel full of coolant mix on the radiator neck, and slap the throttle a few times. On the ones with old fashioned radiator caps, I use a doctored cap with the spring and seat removed so that it seals only around the top of the neck, and as the engine heats up, that lets the system drink from the degas bottle and get rid of its air very easily, but you have to keep an eye on the coolant level in the degas bottle.
Vehicles with the thermostat in the lower hose are obviously easier to bleed than those that have it in the upper hose, because the block tends to fill through the open top hose. I first saw that setup on VW Rabbits and some of the old 2.8L Ford V6s back in the day, but it’s everywhere now. On some platforms I like to fill the block through a heater hose, which bypasses the thermostat. Always check for shop manual procedures on unfamiliar platforms. R.W.M.
One Friday morning I left the house on my way to Dothan, the big town down the road where I worked for so many years. The Ford dealership parts manager had a brand new 7.3L engine block he needed to dump, either on me or in the scrap iron bin. I’m teaching engine repair next semester and the 7.3L block might be a nice training aid, so I fired up my old pickup, left my subdivision, and headed up the boulevard.
The weather was kind of damp and misty, and the old truck tends to skip and carry on in weather like that. It needs a set of wires and a cap, but I’ve been putting that purchase off for years, dreadfully guilty of my own indictments to others about ignoring known concerns, but what the hey? The truck had never put me down… until this morning.
I bought this old Ford for $2000 back in the summer of 1996. Since then, I’ve put about 12,000 miles on it. This 1980 F150 has about 80k miles total on it, so you can see that I almost never drive the old bomb. Don’t get me wrong: I don’t ignore it completely: it has new tires and I recently replaced a leaking radiator with a new one. This is the vehicle I leave at the airport when I fly and at the school when I’m on a road trip in one of the college vehicles. When I start the truck, I have to let the torque converter fill up before it’ll move. That’s how long it sits between drives. People routinely ask me if the truck is for sale, probably because they think I’d sell it cheap because it spends so much time parked on the curb.
When I was replacing the radiator a couple of weeks back, I noticed that all the potting in the ignition module had liquefied and trickled out of the box to re-congeal in waxy rivulets on the inner fender. I don’t know why that happens, but I’ve seen it before, and I knew when I saw it that my truck’s 28-year-old Duraspark module was on its last wheeze. Be that as it may, in true form as wrench guy, I figured I’d take a chance on letting it show me what it had left. It would be a grand adventure, a calculated gamble. Since I’m the only driver, there’d be no danger of my wife or anybody else sitting beside the road due to my lassitude. I did have plans to get a replacement module to toss behind the seat, but never got around to it. Good intentions, that’s all I had going for me.
Well, I wasn’t even at the end of my street before I realized I had big trouble. The truck popped and skipped in a peculiar way that I knew wasn’t related to wet ignition parts. The engine stalled. I restarted it. It stalled again. I noticed that it would stay alive if I kept the ignition slightly past the “RUN” position, a maneuver that keeps the start circuit to the module hot without engaging the starter. That circuit uses a different part of the ignition controller and it wasn’t uncommon when I was at Ford to find that a car would run on the “Start” side of the module but that the “Run” side had failed. The small gray module-mounted TFI modules work the same way.
As I kept toying with the ignition switch, I managed to limp on down the boulevard to the nearest auto parts chain store, which isn’t far from where I live. The truck was idling okay even in the “Run” position by the time I pulled into the Zone parking lot, but I wasn’t going to chance a 60 mile round trip with that used-up module under the hood, and I knew good and well the module was the problem.
The parts store carries a well-known line of aftermarket ignition parts, and the parts clerk sold me a peculiar little replacement module that looked completely different from the OE part except for the bolt holes and the connectors. I opened the hood in the parking lot and plugged it in only to have the engine kick back and carry on like it had crossed spark plug wires or something. I checked the cap for moisture and didn’t find any.
I reconnected my old module and the truck started right up. I reconnected the new module and the truck snorted and kicked back again. It was the classic A-B-A swap that proved the N.E.W. (Never Ever Worked) part was indeed faulty.
Back inside the store (wearing jeans, boots, and a T-shirt, none of my ASE patches) I encountered a skeptical parts guy who had probably seen a lot of yo-yos trying to use his parts for troubleshooting.
“We don’t need to just go swapping parts like this. We need to check your old module to make sure it’s bad.”
“Why don’t we check your new one?” I asked.
We did, using a handy dandy ignition module tester he had sitting on his counter top. The machine checked all the circuits and illuminated the red ‘FAIL’ light. The parts guy looked surprised, but I told him I wasn’t surprised at all. He got another new one and we plugged it in to the ignition module tester. It passed with all green lights.
Back in the parking lot, I tried the same A-B-A swap and got virtually the same results. If I hadn’t seen this module pass the test on the machine, I would have believed it was the same part I had tried before. Once again, the old module started the truck, and the new one acted exactly like the previous new module, green lights on the tester notwithstanding.
Leaving the engine running with my old Ford Duraspark module connected, I walked back into the store to find the skeptical parts guy.
“Can you come out here for a minute?” I asked.
“Sure,” he was more than courteous.
The engine was running. I disconnected the module and the engine died. I connected his new module and it wouldn’t even start. I reconnected my original module and it started.
“Doesn’t that module have to be grounded?” he asked. I groaned but knew how to answer his question.
“No.” I told him. “It doesn’t.” I fingered the harness. “See this black wire? That wire comes from a terminal screwed to the body of the distributor and that’s the only ground this module needs. The orange and purple wires go to the pickup coil. The green wire goes to the ignition coil. The black wire that is grounded in the distributor provides the ground that the module uses to fire the coil. The red and white wires are the “Start” and “Run” circuits. There is no external ground necessary on this box”
He was shaking his head, a little shocked that I knew the system that well, but he remained unconvinced. After all, how much can a guy in faded jeans and a T-shirt know anyway?
We retested the module on the machine. It passed (again) with flying colors. The parts guy was still skeptical. This machine was his go-no-go tester, yet in the last five minutes he had seen one module fail and another one pass on the machine, and neither module would start the truck.
“I don’t know what this means…” he muttered, “I mean, I’ve worked on cars for a long time… ahhh… not professionally, you understand, but…”
“Look, I know what it means.” I tried to be gentlemanly. “It means this machine can’t be trusted. It doesn’t load the internal module circuits the way the module is loaded when it’s firing an ignition coil. It can pass a module with all green lights and the module can still fail to work right. If I had driven twenty miles to get this part instead of being right outside the store I’d be pretty hot. Wouldn’t you be? The acid test of whether these modules are good or not is out there, not in here, green lights or no green lights.”
“Well, I just need to refund your money, I guess, and let you go somewhere else. Do you think you can trust the parts from the other stores in town?” I looked up at the big banner on his store for a second or two. At the risk, of sounding like Mitch Schneider, how could I answer that? Let me count the ways.
“I don’t actually trust any electronic part that doesn’t come from the manufacturer – when I was at the Ford dealer, I don’t know how many times I replaced aftermarket ignition parts to take care of annoying misfires and the like. If I saw an aftermarket ignition part on a car with ignition-related driveability problems I found that replacing it with an OEM part was the wisest thing I could do.”
He gave me back my $23 and I drove down the street and bought a different brand of ignition module that worked like a brand new one. I went and picked up the 7.3L block.
Oh, and by the way, I just plugged it in and let it lay on the fender. When I have time to bolt it down, I will. Until then, it can ride next to it’s failed predecessor. My old Ford doesn’t complain much.
Without pointing fingers at any brand name brand or chain store, that’s the F150 ignition module story. R.W.M.
My mom’s 91 Chrysler had an MIL illuminated, and the flash-out code indicated a cold running engine. Dad replaced the thermostat and got it running normally warm again, and she drove it for a day or two before he got around to changing the oil.
With new oil in the crankcase, it wouldn’t idle, and dad (an old-school mechanic) was so mystified by that development that he called me on the phone to ask about it while he still had the car in his shop. I told him to remove the battery cable for awhile and let it forget what it had stored in the fuel trim tables.
As a cold-running engine, it had also run rich long enough to lace the engine oil with gasoline, the vapors of which were making their way through the PCV system. With no gas in the crankcase, the air-fuel mixture was all fouled up, and until the screwball numbers were dumped, it just didn’t idle worth a toot.
Stories Number Two and Three
My sister once drove a 1977 Chevy Caprice that mysteriously developed an inoperative radio right after my dad replaced the brake pads. She grumbled about the radio and how he must have caused that problem somehow (my dad knew better and turned a deaf ear to her complaints). Finally, I got tired of her tirade and troubleshot the radio problem to find that the radio had a shorted capacitor in it that was causing it to blow the fuse. How did replacing the brake pads cause the radio problem?
They didn’t, obviously. Why the failure happened when it did is probably a Murphy’s Law deal the likes of which we’ve all seen. Customer logic is simple (a little TOO simple sometimes): The item in question was working fine before the car went into the shop and it had a problem after they got the vehicle back, so it had to be something the technician did wrong, and it should be fixed for free. Right? Well, sometimes, but not always, and many a shop has chosen to eat the cost of repairs that were actually the customer’s problem so as not to alienate the customer.
Still, there are times when the customer’s complaint is legitimate, no matter how seemingly unrelated it may be. One of our problems in this business is that with so many customers trying to get piggy-back freebies, we tend to roll our eyes at complaints of related issues when in reality we should be giving them the benefit of the doubt.
For instance, I personally saw my brother’s 1977 Cadillac develop radio static immediately after the tires were rotated. Sound ridiculous? As it turned out, the steel belted tires on that car were older radials that weren’t friendly to being cross-rotated, and when they were placed back in their original positions, the radio static was gone. Really, it was!
This gentleman was qualified to have work done in my department because he has a government job; he had a few concerns he wanted checked. To begin with, the engine was a hard-start long-cranker, and he had the idea that the fuel pressure regulator needed changing. This Blazer was equipped with one of those delightful CSFI fuel systems GM dumped after only a couple of years or so, and at his insistence I had the guys replace the fuel pressure regulator, which was no small feat on that engine. The upper intake had to be removed, and with it a part of the fuel system.
I had my doubts as to whether the regulator was the problem, and we replaced it just to satisfy the customer. The fuel pressure wouldn’t hold steady at engine shutdown, and I was fairly certain it was the pump rather than the regulator, but it didn’t hurt the students to tackle the job. With the regulator replaced, the fuel pressure decay wasn’t any better (not surprising), so I sold him a fuel pump, which handled that hard-start problem. His second complaint was a fairly serious oil leak, which turned out to be a rear main engine oil seal, and I had a different student handle that repair. The transmission was removed, and the rear main seal was replaced along with the transmission pump seal; it would have been a bad bet not to replace that one as well. After all the work was done, everything seemed fine, the bill was paid, and the Blazer went home.
A few days later, the Blazer owner called back to say that his electric rear hatch release no longer worked after we performed our repairs. I have to confess to some eye-rolling here, but I gave the customer the benefit of the doubt and told him to bring the Blazer back so we could have another look. When I spoke to him at length, he explained that the key lock cylinder hadn’t opened the hatch for years, and so he had been accustomed to opening the hatch with the pushbutton switch up front. We were studying electrical systems at the time, and even if the problem wasn’t something we had caused, it would be good for the students to track this one down.
Checking the Hatch from Scratch
First we checked the fuse, then we followed the circuit to the next easiest place; the pushbutton release switch had good power and the power would pass through the switch with the button pressed, but there was no activity in the hatch. I know of one guy who has a short piece of 2×4 with two nails in it. He has a long wire connected to each nail so he can connect the wires to the battery and with the wired-up 2×4 in hand, he takes power and ground with him wherever he goes. Shifting the test light to B+, we checked the circuit feeding the hatch release solenoid and found that there was no ground. Studying that side of the circuit we found that the hatch release solenoid gets its ground through the neutral safety switch; GM didn’t want some yahoo punching the hatch release button while driving down the road. Think about it: You could lose ice chests, camping equipment, dogs, and even kids that way, if they’re riding back there.
To make a long story short (if it isn’t too late), the transmission range sensor connector wasn’t properly seated. As unlikely as it may sound, with that connector poorly seated as it was, everything else that went through that switch would work except the hatch release.
Mustang with a Buzz
This isn’t about a half-drunk horse; I saw a 1996 Mustang that belonged to a retired Air Force fighter pilot, and the car had developed a buzzing noise coming from behind the instrument cluster. I fiddled around for awhile trying to find something and couldn’t pinpoint the noise. The shop foreman noticed that if he held a balled up jacket up at the top of the windshield area, it muted the noise, so we applied masking tape to all the chrome around the windshield, but to no avail. We explained what we had found (or rather hadn’t found) to the old fighter pilot, who told us that he needed the car that afternoon and said he would bring it back later so we could do more checking.
When he did bring the Mustang back, it was to report that he had found the source of his noise. He had been driving with his left elbow on the door and the fingers of that hand on the rain trough when he heard the noise and felt it on his fingers at the same time. He used his finger for a pointer until he felt the strongest disturbance, then held his finger there and pulled off the road. When he stood up to look down his finger, he saw that he was pointing at the edge of the brand new bug shield he had mounted on the front of the hood. The old pilot built some V-shaped aluminum braces and used Velcro to mount them in such a way as to brace the bug shield. The bug shield had been creating an oddball noise that was being telegraphed through the windshield and actually sounded to all of us as if it was coming from behind the speedometer.
- Vehicles primarily produce three harmful gasses and two harmless/beneficial gasses. What are the harmful three? ______, ______,and ______ What are the harmless/beneficial two? __________ and___________
- What gas does the Exhaust Gas Recirculation (EGR) System control? ___________
- What is the optimum air/fuel mixture for the cleanest burn? _________
- Why was it necessary to remove lead from gasoline in the early 1970s?_______________________________________________________
- What vehicle emission does the evaporative (EVAP) system control? ____________
- Black smoke from the exhaust is a strong indicator of ___________ emissions (it’s one of the three)
- What actually happens at the molecular level when fuel ‘burns’ in the combustion chamber? ___________________________________________________________
- What does the term “stoichiometric” mean? _________________________________
- Does alcohol produce more power and fuel economy than gasoline? _________________________________
- During a combustion event, why does the ignition spark ‘burn out’ while energy is still available in the ignition coil? ____________________________________________
- If an engine is running too hot, which harmful gas increases? __________________
If an engine is running too cold, which gasses increase? _____________________