Q. I have a 2004 Chevy Colorado, crew cab, with 38,000 miles. It has a five-cylinder engine, and runs fine with the following exception. The heater/AC fan only runs at the highest setting. I did some research on line and it indicates a resistor in the fan connection can be the culprit. I replaced the resistor with a factory-direct part, and it worked for a few days, but then went back to only working on the 4 setting. I also noticed that even with the setting on 4, if I press the gas pedal, the fan speeds up. Is there a recall, or a technical service bulletin for this problem?

—Jim, Cumberland

A. Currently there aren’t any technical service bulletins concerning the blower motor or the resistor. Before you replace the resistor again, check all the various connections as well as the blower motor itself. The resistor is cooled by the air generated by the blower motor. If the blower motor is binding it could be causing the resistor to heat up and fail.

Changing valve seals

Q. I have been told my car needs valve seals. What is the easiest way to change the valve seals on a 1996 Toyota Tercel? Are there special tools are needed? Or should I just change the oil and put in an additive such as Restore and hope that cures the oil problem?

—Melodie

A. If the problem is the valve seals it is a big job requiring about 10 hours’ labor to remove the cylinder head and replace the seals. The other issue is that many of these engines also have piston rings that stick and cause oil smoke and burning. An oil additive may help but won’t take the place of worn parts.

Homemade coolant

Q. I read your column on the Internet and found it very informative. I am planning to use ethylene glycol bought from a chemical store and use it in my car radiator in combination of 70 percent glycol and 30 percent water. The problem is that quality coolant/antifreeze is not available in this part of the world. The coolants that I have found are fakes with just color dyes added to water. I’m afraid of harming my engine. Could you offer any advice?

—Nadeem, Pakistan

A. Although ethylene glycol is the major ingredient in most antifreeze, there is much more to it than that. As important as engine coolant is to aid against overheating and freezing, there are chemicals that help prevent corrosion and also lubricate the water pump. The other issue is that not all engine are compatible with all coolants. Here in the United States there are at least five different types of engine coolants on the market. Unless you can come up with the exact formulation of a compatible coolant I don’t think I would try to make my own.

Check out strange noise

Q. I have a 2006 Corvette and when the engine is warm I hear a slight noise that seems to be coming from the transmission. I took the car to a Corvette specialist and he has heard of this noise, but doesn’t recommend doing anything about it. He feels that it is more of a characteristic than a problem. What do you think?

—Bob, Seekonk

A. I am not familiar with this noise, but I think you should take the car to the dealer and have it evaluated. Even if the dealer thinks the noise is within tolerance, you will have the noise documented. In this way, if the noise becomes louder after the car is out of warranty, you can approach the dealer and remind him that you brought in the car with the noise while it was still under warranty.

Is Top Tier gas worth it?

Reader comment: Regarding the May 3 question and your reply about Top Tier gasoline, I believe you and that reader have some facts wrong. First, all grades of such gas sold must meet the Top Tier requirements (which means more detergent than in other brands of gas), so you don’t need to pay for premium if your car runs on regular. Second, the main brand in this area on the Top Tier list is Shell, and recently you can get Shell for about the same price as other brands. So your advice to avoid “spending the extra money on boutique gasoline” would seem to be off target. I don’t know if Top Tier gas helps engines, but for the same price I fill up on Shell.

—Jim, Providence

Jim, I agree if you can buy “name” brand gasoline for the same price as “no-name” gasoline, why not buy it. The question is does using top-tier gas help keep your engine clean? BMW, Chevrolet and some other manufacturers think it does, but won’t void a warranty if you don’t. The EPA sets the minimum standards for fuel additives, not the maximum, so if gasoline manufacturers want to increase the additive content they certainly can.

If it sputters, smokes or stalls, John Paul, the AAA Car Doctor{+s}{+m}, has the diagnosis. For an archive of his past prescriptions for car ailments go to: www.projocars.com