Yet another reader's story about the 86 Buick timing gear problems.
I discovered your articles on the timing gears on the 86 Buick after repairing a noise in my wife's 86 Park Avenue and realized how lucky I was to have repaired it when I did. The engine had a random "tumbling rock" sound that only occurred when the engine was hot.
At first, I could not locate the source of the noise so I just ignored it until it became worse. I finally decided that I was going to find the noise. My wife took the car to a couple of shops to get some idea what the noise could be. After one auto repair shop said, "It could be anything" and another said it could be rod bearing noise, piston slap, timing chain, cracked flywheel, etc. I concluded that they didn't know what the noise was either!
I purchased a stethoscope from Sears and began to investigate. I knew it wasn't bearing noise, piston slap or lifters as it did not change with engine speed. The noise was at the timing cover and at the transmission but loudest at the timing cover end. I decided to replace the timing chain, gears, tensioner, and cam button.
When I removed the timing cover, I immediately discovered the source of the noise. The spring in the cam button had weakened and was slapping against the timing cover casting. (The function of the cam button is to keep the camshaft from drifting which would prevent the cam sensor from functioning.) There was an eighth inch "crater" in the boss of the timing cover and the cheap plastic cam button was severely worn. The new cam button was a circular bearing and has a stronger spring. The replacement cam sprocket was all metal.
At this point, I knew that I wouldn't be able to finish the job that day as I had to do something about the damaged casting. When I replaced the timing gears, the camshaft sprocket was cracked in 6 places! It was only a matter of time before it would have disintegrated. I had the timing cover casting welded and machined for $40. A new casting was $200 and junkyards would not sell me the timing cover unless I purchased the entire engine! I re-assembled everything and there was no more noise.
The total cost of the parts and machining was $150 compared with $700+ if I had a shop do the work! I've since learned that this was a common problem with the 3.8L V6 from 1985-1987. I would recommend that anyone with this engine with 100,000 miles from that time period perform this as preventive maintenance.
I enjoyed your site!
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