Q:
I've had to replace the radiator in my truck twice and the heater core three times in the last five years because of corrosion. I use fresh antifreeze, but it doesn't seem to help. What's happening here? A:
If fresh coolant, changed every other year, isn't holding the corrosion at bay, look for one of two problems. First, the combustion gases could be leaking into the cooling system through a bad intake manifold gasket, head gasket or a cracked head or block. You can chase that by sniffing the radiator neck with the probe of an exhaust-gas analyzer. If you can detect any carbon monoxide in the radiator, it's a sure sign there's exhaust leaking in. Second, the corrosion problem could be electrical. Measure the voltage between the battery ground and the liquid in the radiator. Just dip the voltmeter probe into the coolant without touching the side of the filler neck. If the meter indicates any more than a few hundred millivolts--bad news, dude. I'd start by replacing all of the ground wires and clamps connecting the battery to the engine block as well as to the frame and body of the vehicle. Remember, you've got a cooling system with several dissimilar metals (iron, copper and aluminum are all common in engines, radiators and heater cores) wetted with an electrolyte. That essentially creates a big battery, and the electrolysis can eat through thin radiator tubes in short order.
Clutching Techniques
Q:
I had to replace the clutch slave unit on my 2003 Ford F-150. The mechanic wanted to know how I drove the truck. I said that when I stop for traffic lights, I usually leave it in gear with my foot on the clutch pedal. He said that this practice might have caused the slave unit to fail. I've been driving manual transmission cars and trucks for some 30 years and have never had a problem with the clutch before. What is the right way to drive a manual truck or car? Leave it in gear with my foot on the clutch pedal or take it out of gear and keep my foot off of the clutch pedal when I am stopped? A:
I dare say most of the vehicles you've driven, unless they were either a tiddlywink-size sports car or a big rig, didn't have a hydraulic clutch like your late-model F-150. So you may not have seen this problem in the past. Most American iron uses a pure mechanical linkage, or maybe a cable. Regardless, keeping your foot on the pedal while stopped, or in motion for that matter, is poor practice. First, there's a safety issue: Leaving the truck in gear might make it easier to lurch into traffic if you sneeze or lose your concentration and release the clutch pedal. On a more mechanical level, the practice keeps hydraulic pressure on the slave cylinder, shortening the life of the seals. It also keeps the throw-out bearing spinning. Unlike any other bearing in the drivetrain, this bearing doesn't have liquid motor oil, ATF or gear lube constantly circulating past it. The throw-out bearing is lubed by a scant spoonful of grease sealed inside. When this bearing fails, the first step in repairing it is to remove the transmission from the car, which isn't easy or cheap.
Outmoded
Q:
What's the replacement for Type A transmission fluid? A:
Type A automatic transmission fluid (ATF) was a GM specification for transmission fluid back when they still used buggy whips. Well, not exactly: It was first used in 1947 when GM started selling cars with modern automatic transmissions. Type A ATF was superceded by Dexron in 1967, and then by Dexron II and Dexron III. Some power-steering units, convertible-top hydraulic systems and even outdoor power equipment still specify Type A. You should be able to substitute Dexron III in most applications that specify Type A. If you're really compulsive about an older vehicle's diet, you can find true Type A from some smaller manufacturers if you hunt around. Underhood Turbulence
Q:
My wife has a 1990 Lincoln Town Car, which she loves. Recently we've noticed an engine vibration you can feel in the gas pedal. Yet it goes away when we're parked. Is this an engine problem or a transmission problem? A:
Probably neither. If you're feeling the shake through the accelerator pedal and not through the steering wheel or the car's body, then I'd hazard a guess that a motor mount is broken or loose. This will allow the engine to shift under acceleration. When the engine's torque is just right, the mount lifts away from the frame. Feather the throttle just a bit, and the engine's weight holds the mount down. But too much throttle and the motor mount will top out, and things are free to shake. The shaking is then transmitted to your right foot through the accelerator cable. Time to replace that broken mount. Shiftless
Q:
I have a tough transmission question for you. My '93 Mustang GT sometimes won't go into gear. If I'm sitting at a traffic light in neutral with the clutch pedal released, then push the clutch in to put it in gear, the shifter won't go into that gear (or any gear) until I wait to the count of three. At that point, it will go in and out easily--until I let the clutch out with the transmission in neutral again. The clutch cable is adjusted correctly, and I have no problems shifting once the car is moving. I can't figure this one out, and I'm a professional mechanic (albeit for Benz, so we only see maybe a dozen manual trans cars in a career). It's really stumped me and my co-workers; any ideas? A:
Sounds perfectly normal to me. You've got a clutch disc, input shaft and the front half of the transmission spinning along merrily at idle speed, driven by the flywheel and pressure plate. When you step on the clutch pedal, that rotating mass doesn't stop spinning instantly. It takes a second or three to slow down. The 1-2 dog ring in the transmission won't mesh with the first-gear engagement ring until it's nearly stopped. The synchronizers use friction to slow down (or speed up when downshifting) all the whirly bits to allow gear changes. That resistance you feel in the shifter is the synchronizer matching speeds. When that synchro starts to wear out, you'll get a crunching noise. Best practice is to always depress the clutch a few seconds before trying to shift into first gear. This will let the parts slow down on their own. Dead Mule
Q:
I have a 2006 Kawasaki Mule 610. This winter it just wouldn't start--no matter what I tried--choking, no-throttle, quarter-throttle or full-throttle. The battery had enough juice to turn it over, but there was no spark (sometimes just a ppfst, ppfst, ppfst sound). A Kawasaki mechanic told me another spark plug should work. He said, "If it gets flooded, that will ruin the spark plug. It takes a new one to allow the engine to turn over. Just cleaning the old spark plug won't do it." How can flooding an engine permanently ruin a spark plug? A:
When the choke is on, especially when air temps are low, the fuel going into the cylinder tends to remain liquid rather than evaporating, wetting the plug's insulator with fuel. Only fuel that's evaporated and mixed with intake air will burn. After the engine starts and warms up, the fuel gets atomized much more completely--no problem. But until then, all that liquid fuel just soaks everything. The little combustion that actually happens is incomplete and will plate the entire inside of the combustion chamber, including the plug, with a sloppy film of gasoline and carbon and moisture--which is conductive enough to let the spark trickle down the side of the insulator instead of jumping the 0.028 of an inch to the ground electrode and lighting the charge that comes in on the next intake stroke. Continued cranking and partial combustion just makes it worse. A fresh plug fixes that. As far as your mechanic's assertion that the plug will never work again, he's partially right. The oxides and carbon can't really be removed, unless you use a spark plug cleaning tool. I have one. And I've have had it for 35 years. It's just a small sandblaster (although I fill mine with glass beads) that scrubs away all the goop. Problem is, it also rounds off the edges of the positive and ground electrodes, and those work best when the edges are sharp, not rounded. The electrons in the spark like to jump off pointy things, not rounded ones. When plugs had steel electrodes, I used a file to dress the electrodes and then gapped them back to the correct gap. Modern plugs mostly use precious-metal electrodes that don't take kindly to that. I haven't gapped a plug in a new car for years.
I've had engines in motorcycles and cars and power equipment that would consistently take two sets of plugs to get started on cold days. I'd pop in a fresh set to light the fires, warm up the engine, and then put the originals back for the rest of the day. Of course, I had less money and more time back then. Ignition systems are a lot better than they used to be, but sometimes not good enough.
Synthetic Leakage?
Q:
I heard from several "not too reliable" sources that once you use synthetic oil in your crankcase, you should never change back to regular motor oil. I have difficulty believing that, but would appreciate your response. A:
A generation ago, when synthetics first hit the market, there were a lot of complaints about leaky engines. In spite of claims to the contrary by the purveyors of these new, premium oils, they didn't have the same seal-swell characteristics as mineral oils. Mineral oils generally have an additive package that makes rubber and cork seals swell up slightly, promoting a tight, oil-free engine. When you switched to synthetics, the seals would shrink, ever so slightly, and oil would weep. Exacerbating this condition, the synthetics were generally much thinner in viscosity, and would find smaller gaps to percolate through. The result? Speckles on the driveway. Other brands of mineral oil had less seal-swell. These engines didn't leak when filled with synthetic--but the seals and gaskets compressed and wore out in their swollen state. Change back to low-swell oil; the seal contracts to its former, less turgid state, and out it gushes. Fortunately, the petroleum industry seems to have a better handle on that today. Don't worry. Change back and forth as you deem necessary.
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