Engine Knock

[69ra3ta]

Two years ago shortly after I replaced the IP in my Suburban, the engine developed an intermittent knock. I thought that the crank was about to let loose (not uncommon with 6.5 TD's). So I dropped it off at the shop and had them try to diagnose the source of the knock. They thought it was the injectors and not the crank / rods. I had the injectors replaced but still have the knock.

The knock sounds like a rod knock. I usually knocks when cold and goes away when it warms up. I have good oil pressure and have no shavings in the oil. I figured it would fail, but it has been 2 years.

I have checked for exhaust leaks, harmonic balancer, injectors. It does not sound like lifter noise.

I have since put on about 35K miles (long road trips and towing) since first hearing the knock. It has not gotten any worse.

Any ideas??

[Turbo Al]

Just before your next oil change dump a quart of ATF fluid into the oil and run it for 100 miles or so. Worked everytime on my 1993. My knock came and went for over 100,000 miles area of the #6 piston under the Turbo.
Al

[john8662]

Check to see if the heater hose (metal line) going to the firewall is anywhere near touching an injector line, it will make a knocking sound that will be plainly heard in the cab.

Is this noise heard readily outside in the engine bay?

J

[sailun]

I had the same knock-when-cold problem for 100k+ miles. Tried Turbo Al's ATF fix, I was very skeptical, but it got way better.

With warmer weather in the morning, and new injectors, it's pretty much disappeared.

[69ra3ta]

Turbo Al - Thanks for the recommendation. I will give it a try.

john8662 - I checked the heater hose. It does not seem to be the problem but thanks for the tip.

sailun - I am glad that Turbo Al's remedy worked for you. I hope it works for me as well. I will keep everyone posted.