1998 Chevy Tahoe Engine knock

HAROLDLC

MEMBER
1998 CHEVROLET TAHOE
V8
2WD
AUTOMATIC
203,000 MILES

I just had engine rebuilt by a local engine rebuilding firm because I had a bottom end knocking noise that seemed to be a front main bearing. Now after a complete rebuild with approximately 300 miles on the engine I am hearing the same type noise. The builder said it may be a distributor bushing noise. Any thoughts on this frustrating problem

1 Reply

PEAR69

MECHANIC
1,482 POSTS

When these L-31 Vortec engines were first introduced, some had a knock issue with main bearing no. 2. However, being that you had a complete rebuild done at 200000, it is safe to assume your engine did not have this problem.
The distributer gears wear out on these distributers, but if the engine shop is good they would have replaced that as part of the rebuild. There is no "distributer bushing" on these distributers to go bad. Your engine has hydraulic roller lifters that can leak down causing a knock --- but then again, a reputable engine shop would have replaced lifters with 200000 miles on them. If you rebuilt the engine because of this knock, thinking that it was caused by a main bearing issue, the rebuilder should have (and easily could have) told you whether or not it was a main bearing. IMO - a properly rebuilt engine needs around 1000 miles of variable driving to properly break in. There will be some knocking as the rings set and the bearings wear in. After 1000, you should change the break in oil (which should be in the engine) and see if the knock goes away, but make the rebuilder aware of your conserns.