Don’t put off professional repair on slow tire leak
Q: I have a tire on my SUV that loses air to the tune of 4 to 5 psi per month. I’ve looked for a nail or screw in the tread but have found none. What is your take on adding some of the tire sealant to stop the leak? My busy schedule makes it difficult to take it to a place to be fixed? — Janice
A: While a sealant would probably mitigate a tiny leak such as this, perhaps for a while, I wouldn’t do it. I carry a can in each vehicle for a possible badspot-for-a-flat situation, but I would hesitate using it in an elective case.
The fault could worsen, and even though some sealers are touted as TPMS (tire pressure monitoring system) safe, it’s best to make the time for a pro repair. (Also, save a future tire replacement technician’s sanity: Sealers are super messy!) A sneaker leak like this may at some point be accidentally neglected, and an SUV is the worst possible vehicle,
stability-wise, to have a low tire condition.
Is the valve stem cap present? If not try replacing it.
Q: I just adopted a 1999 Chevy pickup from my dad that wasn’t being used. It runs great but I am concerned about a clacking noise from the engine right after a cold start. It lasts for about 30 seconds and is getting better now that the weather is warming up. Ideas? — Jim P.
A: This sounds like a harmless case of piston slap, a condition where the piston-to-cylinder clearance is a bit wide and the piston rocks in the bore as it passes top dead center. A sometimes sloppy original fit when the engine was manufactured compounded by a short piston skirt (reduces friction/improves economy) and normal wear can lead to this noise. As the piston warms up and expands, skirt-to-wall clearance decreases, and the noise typically goes away.
Brad Bergholdt is an automotive technology instructor at Monterey Peninsula College in Monterey, Calif.