Q My 2000 Saturn SL1 runs well at 130,000 miles, but it has a problem with the air conditioning. The mechanic tells me that the compressor is shot and there is a small leak that could be easy to fix. The problem is that he cannot find a used compressor, and a new one costs close to $900. Adding the install, patch of the leak and the refill, it will end up near $1,200. If we put $1,200 in addition to the $500 we recently spent on tires and a battery, it will exceed the value of the car. Can a compressor be repaired? Or, where can I find a used compressor that will keep me on a $500 budget including installation?

A Yes, an air conditioning compressor can be repaired or rebuilt, but your best bet is a new aftermarket or a professionally remanufactured compressor. Checking with popular auto parts stores, I found compressors in the $350-$500 range, and online I found remanufactured compressors in the $250-$350 range. I'd stay away from used compressors -- I've not had much luck with these.

Also, I'd get a second opinion and shop around for the most competitive price on the repair.

Q I have a 1992 Toyota with just more than 100,000 miles. A couple of months ago, I heard a clicking noise that I thought came from a wheel bearing. I took it to two shops and had it checked out. No one could find a problem. At the third shop, the only thing they could think of was that the pads were dirty. So they cleaned all the pads, and it worked -- for a while, anyway. Now I hear the noise again. Can you give me some other suggestions that I can tell him to try?

A Do you hear the noise only when you reverse the vehicle's direction, such as moving forward after backing up, or vice versa? The brake pads must have clearance in the brake caliper to move in and out as the brakes are applied and as the pads wear.

That clearance also means the pads can move forward and backward in the caliper as the brakes are applied. If, for example, the pad has moved forward as brake pressure is applied while traveling forward, when you back up, the pad can "click" against the caliper as it moves backward. This is not dangerous or harmful, and resecuring the pads in the caliper or applying a very small dab of high-temperature silicone grease to the pad support plates might eliminate the noise.

Q I have a 2001 Pontiac Grand Prix GTP with 137,000 miles. I have changed the transmission fluid and filter every 25,000 to 30,000 miles. I ask the service technician to drop the pan and replace the fluid instead of using the newer fluid exchange system.

Recently, I have noticed that after warm-up, when I move the transmission from drive to reverse, there is a delay of 3 or 4 seconds before the transmission engages. As a result I find myself unconsciously applying the throttle before the transmission engages, which causes it to clunk abruptly. Is the transmission living on borrowed time? Do you have any suggestions?

A Because only about 20 to 25 percent of the fluid is changed when the pan is dropped to change the fluid and filter, I'd suggest having the fluid exchange service done. This exchanges 100 percent of the fluid, leaving the transmission filled with completely new fluid. It also helps flush the valve body, since the exchange is done with the engine running, hopefully cleaning any varnish that may be gumming up hydraulic pistons and accumulators. Also, try an additive to help that cleaning process. And finally, discipline your right foot to wait patiently for the transmission to engage before adding throttle. This will certainly help extend the transmission's life.