Q–My 1952 Pontiac started overheating last year after the engine was overhauled. It now has 3,000 miles on it. The radiator checked out OK, the thermostat was replaced and the heater bypassed. A new water pump was installed and the head gasket was replaced. Can you think of a cause for this problem? G.B., Chicago
A–In our experience, the most common cause of overheating after an engine overhaul is the head gasket. Often it is installed wrong or may be the wrong one for the engine. When it was replaced, it may have been replaced with another of the wrong design. If any coolant passage holes are blocked by the gasket, overheating is certain.
Q–My ’91 Mazda 626, with 2.2-liter fuel-injected engine recently developed a “high” low idle. I suspect the air bypass valve may be the problem but would it affect cold engine r.p.m.? J.P., Morton Grove
A–When a fuel-injected car begins idling too fast, the first thing to look for is a leak. Not a coolant leak, but an air leak. Air is getting into the engine without passing through the throttle body. Ask your technician to carefully inspect the vacuum hoses and intake manifold gaskets for leaks.
Q–I have a 1990 Chrysler Town & Country van. No one seems to be able to determine what is causing the engine to die after it has warmed up and a load, such as the air conditioner or turning the steering severely left or right, is placed on it.
If I turn off the A/C or defroster, it runs fine. So far they have replaced the TPS (throttle position sensor), spark plugs, timing belt, distributor cap, oxygen sensor, AIS (automatic idle speed) control motor, gaskets (head and throttle body) and even substituted a main black box. Please help. I can’t afford to trade this van in on a new one.G.J., Oak Park
A–We were going to suggest you have the throttle body cleaned, which requires it be removed from the engine to be done right. However, we assume that was done since your idle speed motor and gasket were replaced.
We now suspect an electrical problem such as a bad or corroded ground connection or corroded connectors. The computer bumps the idle speed up when it is told there is a load, and we think it is not getting the message.
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Bob Weber is an ASE-certified Master Automobile Technician. Send your technical questions about cars to him in care of Motormouth, 17717 Silcott Springs Rd., Purcellville, Va. 20132. Send e-mail with name and hometown to motormth1@aol.com. Answers are supplied only through the newspaper.
