Knock

[suffolksnowbird]

Hi: I'm a new guy on the block. We (my son and I) just purchased a "new to us" 1998 GMC 2500 6.5 turbo diesel originally owned and operated by VDOT. We seem to be the 3rd owners since it was state owned. We bought it at a bargain price because of the loud knock and the code message that No. 6 cylinder was not working. Thought it might be an injector but with all new injectors have now been able to hear a very loud knock in No. 6. The body of the truck is in excellent shape for it's year, but the engine has 396,752 miles. Should we tear it down and rebuild it or just worry about the No. 6 cylinder? :confused:

[DmaxMaverick]

Welcome aboard!

If you've eliminated the injectors, I suspect a repower will be in order. A rebuild or replace will depend on what you find on disassembly. With that many miles and a very loud knock, the likelihood of broken crank, main or some other more serious issue is much higher. You've already dealt with the possible #6 fix about as much as you can, so anything further will be an overhaul.

[suffolksnowbird]

Thanks for your thoughts on the situation. You answered our concerns with a confirmation for pulling the engine and checking out the insides. We sorta thought that was gonna be our "need to do." We have the garage, the chain falls and the engine stand. Appreciate your experience. We shall keep on learning and post the outcome.

[a5150nut]

Hope you have a stout engine stand. These 6.5s aren't light.

[JeepSJ]

Hope you have a stout engine stand. These 6.5s aren't light.

Bought a heavy duty unit from Harbor Freight. I scrapped all the cheap hardware and used grade 5 stuff everywhere. Works nicely.

[suffolksnowbird]

Great Idea. Will do the same. Our stand has seen a few engines but they were not 6.5's. Thanks.