Q: I have a 2001 Buick Century with a cooling sensor problem. About six months ago the check coolant level light came on and I discovered a leaky intake manifold gasket. About a week after the gasket was repaired, the light came back on. The radiator level was OK, so the coolant level sensor was replaced.

After another week, the light came back on again and the sensor was again replaced. We are on sensor No. 4 and the light is back on again. What do you think is wrong? – W.L., e-mail

A: According to technical service bulletin No. 04-06-02-007M, the sensor could be contaminated with oil. If that’s the case, it shouldn’t merely be replaced each time without first finding the source of the oil.

Oil contamination in the coolant could be the result of a bad intake manifold gasket or cylinder head gasket. Since the intake manifold gasket was already replaced, I would have the cylinder head gaskets carefully inspected. A technician can use a block tester to see if combustion gases are getting into the cooling system.

Also, a technician can pressure test the cooling system and use a borescope in the cylinders (with the spark plugs removed) to check for the presence of coolant in the combustion chambers. If everything checks OK, the cooling system should be thoroughly flushed. It’s possible that remnants of engine oil are still floating inside the cooling system and contaminating the coolant level sensor.

Q: My wife owns a 2005 Toyota Camry (four-cylinder) with 30,000 miles on it. Whenever we turn on the air conditioner we get a moldy smell from the vents. The smell usually goes away after a few minutes of run time but it is really bad while it lasts. We are wondering if there is anything that can be done to repair this. – J.H., Orland Park

A: Usually a moldy smell is the result of trapped moisture or moist debris trapped on the evaporator. First, I would recommend that the cabin air filter be inspected. It’s located behind a cover that is accessible once the glove box is lowered out of the way. Replace it if it’s wet or dirty.

If the filter is OK, have the evaporator drain checked to make sure it’s not restricting the release of water from the evaporator case. Also, the surface of the evaporator should be checked for debris. It may need to be cleaned. The most economical way to do this is to remove the blower motor.

Auto parts stores sell aerosol products that can be sprayed on the evaporator fins to clean it. But before you attempt to clean the evaporator fins, make sure the water drain is not clogged.

Q: I recently brought my 2005 Ford Focus in for an alignment because it was pulling to the right and wearing out the tires. The alignment shop called me and told me that there would be an additional charge to first align my car’s subframe. I told them forget the alignment. Have you every heard of this? – S.P., e-mail

A: Yes, I have seen cases where the subframe was out of alignment and needed to be adjusted. In fact, Ford issued a technical service bulletin, No. 07-4-2, to address this concern for your Focus.

Questions for Ira Siegel? Call the Auto Advisor Hotline at (708) 633-6839 or e-mail autoadvisr@aol.com. Siegel is an automotive instructor and an automotive service excellence certified master auto technician.