Air Flow Pattern Could Be Expensive Problem
Question: I do not use either the heater or the air conditioner on my 1981 Oldsmobile Cutlass Calais. It’s just a habit. But even with the mechanism in the off position, I find there is an air flow from the dashboard vents, which ranges from cool to warm. I questioned my mechanic, who ran a computer diagnosis and could find no problems. Can you explain it? S.K.
Answer: The air flow you are describing may be part of a safety ventilation system built into many cars, in which the blower fan operates even when the heat and air conditioning controls are in the off position.
Federal regulations require that the passenger compartments in cars have a positive pressure, so that poisonous carbon monoxide gas cannot enter the car if the exhaust system has a leak.
A vacuum condition was created in many older cars by air flowing around the passenger compartment, an effect known as a venturi effect. Then, if the exhaust manifold or exhaust pipe leaked, gas could be sucked in.
Your 1981 Cutlass has a positive ventilation system, though the air is supposed to enter through the ducts at the floor, rather than the dashboard.
If you are correct that the air is all entering through the dashboard, it is possible you have a problem. The vent channels are controlled by small doors that are closed and opened by using vacuum power from the engine. Other cars use small electric motors or manual cables from the board control unit. Sometimes, the doors become stuck or warped, preventing them from either opening or closing.
The cost to repair such problems can be quite high or very low, depending on which doors are at fault. If the problem is behind the dashboard, you could easily pay several hundred dollars to remove the dashboard and all of its wiring and tubing.
Q: I own a 1988 Acura Integra LS. Several months after purchasing it, the brakes began to squeal loudly. The dealer told me that was normal. Then, at only 7,000 miles, I was told the brakes were only 80% good. Could they be defective?M.A.
A: At the rate you are wearing out your brakes, you should get roughly 35,000 miles out of them. That is about normal, especially if you do a lot of city driving.
The squeal, unfortunately, is common, though you might not consider it normal. It is becoming commonplace because brake manufacturers have turned to metallic-type brakes in recent years as asbestos is being phased out.
The metallic-type brakes contain tiny grains of metal that provide for long wear and resistance to brake fade. But they also tend to glaze and make a high-pitched squeal. So, while your ears are ringing, you can at least be happy that you are not breathing asbestos, a known cause of cancer.
Q: My 1987 Chevrolet Caprice loses a half-gallon of coolant every month. The oil shows no signs of dilution with water and there are no external leakage stains around the hoses or engine.
What might be the cause of the leakage and could the engine suddenly overheat? M.E.
A: A half-gallon of coolant is a significant monthly loss. You need to have a pressure test run on your cooling system.
A mechanic will remove the radiator cap and install a special gauge that will pressurize the system. It will determine if the system can hold pressure.
If the system is leaking, the pressure test will help find the cause. Leaks such as yours often occur around the water pump bearing seal.
The bearings can fail, causing rapid loss of pressure and coolant. The car could overheat and be undriveable.
Other causes of leaks include poor hose connections, a relatively minor repair, and leaking head gaskets, a fairly major repair.
