Question for you Diesel "Experts"

[BisonTech]

Ok, this will be long and vague, so pay attention.

I was at a customers jobsite working on a forklift with an electrical problem. My customer started asking some questions about a lift that was previously fixed by an ex-mechanic of ours last year. The Ex-mechanic was suppose to be more of a "Diesel Engine Guy", where I am more towards small engines/ gasoline, electrical, and fabricating.. Forgive me, I didn't take note of the make, model of the lift in question. It does have a Cummins (with a Holset turbo that would fit nicely on my 89 Turbo Caravan- 5 speed..blah blah blah) Now the engine had a knock, our mech went through and checked the bearings n such and found nothing wrong. My customer said it sounded like it was in the upper end almost like detonation. My customer found a plate wheere the air comes from the turbo and goes through [this plate] and also houses a heater. Now this plate has 2 broken bolts, which then is obviously creating a boost leak..

Could this boost leak richen up the fuel enough to raise the EGTs and cause DET at idle??

I know this was vague, so if you need more info please ask... I don't have a lot more but ask anyway.lol

[skata]

a boost leak would be more evident under load, not at idle. only knocks at idle?

[TCS]

True a boost leak at an idle would contribute to none of that at idle,the most might be a compressed air sound under load,maybe some smoke and loss of power. From the little info, you offered it sounds like it may be a B-series Cummins,either a 4 or 6 cylinder.The test for a bad wrist pin or piston skirt would be to crack each injector line at the injector,killing that cylinder to see if the noise disappears. I will add that the B-series is prone to head bolt failure when they get a lot of hours on them. That in turn causes head gasket failure which if the failure is on the atmosphere side rather than the internal side can sound just like an upper end knock at idle. Good luck.

[BisonTech]

Thanks guys!

TCS I know it is a 4 Cylinder (4BT maybe?). We did crack the injectors and there was no change in sound. I did remove the head and had it sent to be rebuilt by a well known, local, reputable engine builder. Hopefully the noise goes away after this. I appreciate your responces.

Nate Hopkins
Bison Scaffold