PRACTICAL VIEW : Older Engine May Need Rebuilding
Question: My 1981 Toyota Celica, which I thought would last forever, has recently begun rumbling while idling and occasionally stalling unless I rev up the engine. This started after I overheated it recently, but several mechanics haven’t been able to diagnose it without tearing apart the engine. Am I looking at a complete engine overhaul?
--C.E.S.
Answer: You undoubtedly had some engine damage when it overheated. A mechanic should be able to give you a rough idea of how much it will cost to fix. But it doesn’t make sense to spend a lot fixing an 11-year-old engine without rebuilding the whole thing or installing a remanufactured engine.
The stalling problem most likely means the cylinders have lost some compression. The rumbling also indicates some moving parts have been seriously damaged by heat or lack of lubrication.
If the problem is in the rings--the circular metal inserts in the pistons that seal them--the repair will require complete disassembly.
It is possible, though unlikely, that one or more of the engine valves have been burned and are leaking. That would be a less expensive fix. Again, a trained mechanic who can do a cylinder-compression test and leak-down test should be able to diagnose the problem.
Finally, if the car runs acceptably, you may want to drive the engine into the ground. You might eventually get stranded, but if you accept that risk, you have little to lose.
Q: Can crossing railroad tracks that have big bolts extending above the road surface damage tires? My tires have large chunks of rubber missing. What causes this? --V.S.
A: When a tire loses a piece of rubber, it is commonly called chunking out. But the railroad crossing is an unlikely cause. Bumps can be cumulatively hard on a tire, but any single bump seldom hurts.
To cause real damage, you have to ram a curb or a pothole with enough force that the sidewall folds over the rim flange, and you get a rim bruise. It seldom happens to radials, though, because their sidewalls have greater strength than bias-ply tires.
If your tires are chunking out, it may indicate a manufacturing defect. If the rubber did not flow properly into the mold, the tire may have a void or weak spot in the tread. As the tire wears, the weak spot will eventually fail, and the rubber will chunk out.
The same thing can happen if the tire gets very old, even though it may not have many miles on it. Sunlight and pollution make the rubber brittle and weak.
Q: All my life, I have checked the oil when the engine is cold. Now a relative tells me I should check when the engine is hot. Who is right? --M.C.
A: You should follow the procedure laid out in your owner’s manual.
Some manufacturers recommend checking the oil when it is hot, but advise waiting a few minutes after the engine is shut off to allow the oil to drain to the pan.
Beyond the first few minutes after an engine is turned off, only a moderate quantity oil of drains down. The more important thing to remember is to check the oil regularly.
