7 Car Mysteries Solved: Expert Car Clinic

• auto clinic
• auto repair
• DIY
• radiators
• motor oil
• engines

I’m Melting

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?

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

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?

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

What’s the replacement for Type A transmission fluid?

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.

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