New timing belt or new mechanic? Maybe both.

Dear Car Talk

Dear Car Talk | Oct 01, 1992

Dear Tom and Ray:

I have a 1986 Renault Alliance. Last spring, the timing belt broke, and as a result of it breaking, I had to have the valves replaced too. After the repair, every time I drove the car up a steep hill, the valves would peck very loudly, and the car would lose power. In order to keep the car running, I would have to pull off to the side of the road and put it in park for a few seconds, then take off again. I explained this several times to the mechanic who fixed the car, and each time he told me something else was causing it. This summer, the timing belt broke again, and the same garage fixed it. Yet I'm still having the same exact problem when I drive up steep hills. Do you have any idea what the problem is?

RAY: I think the problem is your mechanic, Phyllis. He may have installed the timing belts incorrectly.

TOM: When he installed the first belt, he may have either over-tightened it, or under-tightened it. That would explain why it broke again so soon.

RAY: It's possible that incorrect installation is causing the lousy performance, too. The timing belt is a notched, rubber belt which connects the crankshaft to the camshaft. The camshaft, in turn, controls the opening and closing of the valves. If these two shafts aren't lined up exactly right when the timing belt is installed, then the valves won't open and close at the right time.

TOM: That would cause the car to run lousy all the time. Of course, since this is an '86 Renault, you're probably accustomed to it running lousy all the time. So you wouldn't have noticed any difference, except under the most extreme climbing steep hills.

RAY: But more likely, the lousy performance is the result of damage done to the cylinder head when the first belt broke. If the cylinder head was damaged in that incident, the valves could be sticking, and that would also cause the performance problems you describe.

TOM: In that case, your mechanic is also at fault for not noticing it. And if that's true, you need a new mechanic AND a new cylinder head. Good luck, Phyllis.

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