Q. My ’94 Plymouth Grand Voyager has been without heat for some time. After replacing the thermostat without success, I was told the problem was the heater core. I had that replaced, again without success. Next, they replaced the vacuum tubes. The temperature gauge maintains a normal reading. After many trips to the shop, and hundreds of dollars, I am still without heat. They tell me the heat works when it is idling in the shop, but when it is driven the air turns cold. They want to replace the water pump next. Do you think this could be the problem and if not what is it?

A. If the engine isn’t overheating, I wouldn’t suspect the water pump. Have the repair shop check for a possible cylinder head gasket leak. At times when head gaskets leak they will cause an air blockage in the cooling system. The symptom is normal heat at idle and loss of heat at highway speeds.

Rodents under the hood

Q. I recently had a problem with my Chevrolet Blazer. I took it into the shop and they told me a rodent had built a nest in the air cleaner. The mechanic cleaned everything out and the truck runs great. Does this kind of thing happen often?

A. From time to time mice, moles, rats and squirrels will build nests around warm areas of an engine. Usually these critters are attracted to the area due to a food or water source. If you have bird feeders or pet food near where you park your truck, this might be part of the attraction. There are several items sold to keep mice away. One that is humane is a strong-smelling peppermint scented packet (it looks like a tea bag). Short of buying a cat, you might want to give this a try.

Head gasket leaking oil

Q. I have a 1993 Nissan Sentra with 176,000 miles and I took it to be serviced and inspected yesterday. The mechanic said that I need to have the engine gasket changed due to an oil leak. Is it still OK to drive and how long will it last?

A. If the oil is leaking on the hot exhaust system this could potentially be a fire hazard. Other than that possibility, as long as the oil remains full you should be able to drive the car without any problems. I should mention, however, that having oil leaking on the ground is not very good for the environment.

Milky white on dipstick

Q. I recently bought a 1968 Plymouth with a 318 cubic inch V-8 engine. The car runs great and has only 80,000 miles on it. The problem is after the first time I changed the oil I noticed a milky white substance on the dipstick. I have changed the oil twice since and this stuff is still there. I didn’t notice it when I first bought the car. I have been told this could possibly be the result of a faulty head gasket. I have changed the coolant and haven’t noticed any loss and the car doesn’t overheat. Do you have any advice?

A. It is quite easy to check for a faulty head gasket. A technician will use an exhaust gas analyzer or a chemical leak check kit (kits are available at NAPA auto parts stores for $50.00). Both methods test for combustion gases in the radiator, which would signify a problem. The 318 engine was not prone to head gasket or block failure. I would check the PCV system, including the breather cap, and test to see that the engine is getting up to operating temperature. A cool-running engine with a partially clogged PCV system will build up condensation.

Time for a timing belt

Q. I have what may be a stupid question. I drive only about 5,000 miles per year in my Hyundai Elantra. The car is now eight years old and has about 42,000 miles on it. Should I replace the timing belt? Also, did I hear you co-hosting the automotive program on WPRO one Saturday afternoon?

A. The only stupid question is the one that didn’t get asked! Hyundai recommends replacing the timing belt at 60,000 miles or every 48 months. The engine in your vehicle can be severely damaged if the timing belt breaks, so it would make sense to replace it now. Yes, from time-to-time I fill in for one of the Zangari brothers who host Drive Through Radio on WPRO.

projocars@projo.com