Just got a 07 Dodge Cummins 5.9 w/53,000 miles about 6 months ago. When it is idling, I have a gear slapping noise on the front of the engine. The best way to describe it is a hollow gear slapping noise. It is most noticable once the engine starts to warm up, a few minutes after starting it. The truck seems to run fine? At first I thought the noise was coming from the exhaust side of the engine and was a lifter knockng, but after crawling up inside the engine compartment and putting my head practically on the exhaust manifold, i realized it was just echoing inside the engine compartmnet and was coming from the front of the engine. I am assuming around the cp3 pump. I had it to the dealer and got the usual song and dance, nothing wrong! said there were no codes, everything fine. What idiots! If there were somthing wrong internally, it probably wouldnt throw a code anyhow! worried I may have a problem, any help would be appreciated. Oh, by the way, no modifications to truck yet, bone stock except for a banks monster exhaust, cat back. Thanks!

 

Mine did the same thing, Bro. However, I was able to figure out fairly quickly what it was. I'm not saying that you don't have something different going on, but it sounds identical to what mine was. Once the engine warms up a bit, mine would make this "Whump" sound that I could hear, and just about feel, from the drivers seat. "What On Earth?", I thought. I just got this darn thing. So I popped the hood, and watched. WHUMP! The entire engine looked like it moved on the mounts, and I got really concerned. Traced it around, front of the engine, A/C compressor fan kicked on and the pulley went from a dead stop up to what the idling engine RPM was. WHUMP! "Ah-ha! So THAT's what that noise is, eh? Think I'd better keep an eye on it." That was over 2 years ago, and it's never been a problem. Pulley is tight, belt is good, engine lurches a bit from the instantaneous load a little, but all is well with the Cummins. 50,000+ miles it's been doing it, that's the entire time that I've had it.

See if that's it. I boggled me for a bit, too. Didn't think it could possibly have been something so simple, but it was. See if your A/C lines and hoses jump when it happens, and then you'll know that you have the same thing that I have, and it's really no big deal. At least to me it wasn't. Get a good aftermarket performance exhaust, and it'll go away. Or, at least, the noise will.

 

That sounds like a problem I could live with.

 

[B]Update:
Did some research and found that guys have been able to eliminate this noise by re timing the cp-3 pump. It involves removing the gear off the cp-3 pump and rotating the engine 60degrees and re installing the gear. I did this procedure today and it absolutly cured the problem! No more annoying gear slapping (knocking) noise, and it was relativly easy to do.

 

you should give us a link or a writeup as to how to do this?

 

DANG IT!!! And here I thought I might actually be able to HELP someone this time instead of always having people be smarter than me!

Can we change the subject to helicopters?