What a resource! Very glad to find this and be a part of it as of now. Bought a 96 dually w/ 5-sp manual and 220k miles yesterday. This truck has a terrible knock sometimes but then goes away after an hour or so(comes and goes) while the knock is present I have removed all valve covers to observe valve train operation and it seems to be good. Have also loosened all injector lines but makes no difference in the knock. Sometimes when this knock appears it causes excessive blowby while other times it does not. It's got me stumped.Thankyou for any ideas.

 

How is the oil pressure looking?
-P

 

It has'nt changed any. around 60 psi.

 

Injector Knock (leaky injector) maybe?, my 98 12 valve had one this summer that would come and go, sounded awfull, anyways replaced the injectors and had no further trouble, they pop tested them but could not find the leaky one (hence the come and go), but it never returned after I did them all,

Cheers

 

Thanks for the tip on the injectors. I completly removed the lines from each one and the knock still persists. I,ve had prechambers and glowplug tips fall into cylinders on my chevy diesels. Is there anything on a cummins that might fall into the cylinders and cause a knock? Thanks

 

elevatorman -

Welcome to the site! Sorry however that it seems you're having trouble early on like this. Might go ahead and take a second to fill out your year, type, transmission in your signature so it's easiest to help diagnose.

Now to the knock...is it an upper-end sort of knock? Perhaps I'll guess so since you've been looking there already? Possibly injectors, but I've not had this issue so far. Now if it's lower down, in the block itself, maybe (I hope not) it's something more like main bearings? Just hazarding a guess, of course. If it's something like this - or even injectors, I would give serious thought to contacting the seller of the truck. Did they mention anythig about an intermittant knock? If not - and you can demonstrate it to them, you may be able to get it repaired or your money back from the purchase.

Good luck - let us know how it turns up.

 

The seller disclosed the info about knock. I gave 3k for the truck which came w/ new tires and all factory options in pretty good shape so I'm not losing even with doing a rebuild. Your probably right about the lower end. I'm pulling the oil pan in the morning and will update this posting w/ what I find. Thanks

 

Not bad at all! Even with a rebuild you still are looking at a great truck after a little work. You could bomb it a bit as you do the work to it as well. Search on bomb - be careful, money tends to get sepnd this way.

Good luck...hope you find good & not bad bearings under there.

 

Cracked piston. Bought another engine today out of a low mileage 93' to run during the overhaul. Actually bought the whole truck(my wife is soooo proud) Thanks everybody!