Automania/Repair & Maintenance

Auto Questions And Answers For Week 44 Year 2001

by Bob Hagin

Q. When a young relative drives up our steep hill to visit our Big Bear home, she must stop occasionally to let an overheating condition dissipate. Running the interior heater is of some help. Can you name some likely causes for this '94 Volkswagen Jetta difficulty?

A. Your letter is sparse on details such as the configuration of the engine (four-cylinder or V6), stick-shift or automatic, how many miles the car has on it, if it loses coolant and the overflow tank has to be topped up, if she has had a professional mechanic check it out, etc. Hopefully the car hasn't overheated for very long because prolonged overheating can only aggravate the problem. Continual overheating can warp a cylinder head or even crack it. To analyze the problem, someone should check the cooling system to see if it will hold at least 17-pounds of pressure and if the radiator cap itself is holding pressure. The temperature-controlled electric cooling fan should be checked to make sure that it's working at all and/or is coming on when the coolant reaches the right temperature. The coolant should be checked to make sure that it's at least 50-percent antifreeze. If the coolant hasn't been changed very often (once every two years is about right), the circulation of coolant through the engine may be blocked with the sludge that's formed by galvanic action and in need of a reverse power-flush. Other mechanical caused could be incorrect ignition timing, a fuel mixture that's too lean, debris up front blocking the flow of air through the radiator and even incorrect or worn out sparkplugs. She should have the car checked out pretty quick to avoid a total meltdown.

Q. I have never owned any vehicle long enough to encounter this question. I have a 1996 Mazda B3000 pickup with an automatic transmission. I purchased it at 46,000 miles in '99. It now has 100,000 miles and is my daily driver but it has had four round trips from Virginia to Texas since '99. Should I have the transmission pan pulled and a new filter installed? It has not used any fluid although it is dark. I'm heading for Texas again after Christmas and I don't want to have any problems along an interstate highway.

A. If an automatic transmission uses ATF (automatic transmission fluid), it may already be too late for a change to do any good. At 100,000 miles, an ATF and filter change is a good idea and flushing the torque converter couldn't hurt either. Hopefully the transmission pan has a magnet in it somewhere to pick up bits if iron that may have developed there and also hopefully it won't have anything on it. You might want to have the bottom of the pan checked for non-ferrous bits of brass and aluminum too. Although vehicle makers promote the idea that automatic transmissions will go a long way between ATF changes, I've seen too many of them fail prematurely to believe that sales rhetoric.

Q. I have a '73 Ford one-ton Super Camper pickup wit a 460 engine. It has disc brakes on the front. Several years ago, under very hard braking, a red light came on on the left side of the instrument panel. It is very distracting even with a strip of electrical tape over it. I was told that it was the brake proportioning valve and indicated a problem with pressure feed to the front brakes. Ford doesn't stock it anymore and I haven't been able to find one in a wrecking yard.

A. I don't have a manual on that truck but I've been successful in resetting brake proportioning valves on other vehicles. It involved "cracking" the brake line that fed the rear brakes and applying brake pedal pressure to the front brakes to center the switch plunger. Your search for a new valve may require some exploration on the internet.