12 valve billet tappet cover leak

S

Shenian508

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Jul 6, 2015
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Anyone ever have any issues with a JD machine billet tappet cover? I have a brand new one on my 96 12 valve, I cleaned it thoroughly, tightened it and retightened it but it continues to leak just behind the back of the injection pump. Has anyone else had trouble with this cover or do I just have terrible luck? Maybe I'm not doing something correctly? Here is the part, any input is appreciated as I'm quite frustrated with it. http://cppdiesel.com/jd-billet-tappet-cover/
 
Are you positive that the cover is what is leaking? Could it be the timing case?
 
Where is it leaking from exactly? Did you remove all of any residual oil from the bolt holes?

Jesse has recommended now for sometime that installers put RTV silicone beneath the heads of the bolts.

I have one of Jesse's covers and the only "leaks" I had after installing it was minor weeping from behind the bolt heads. I blame myself for not cleaning the bores better. My engine's been rebuilt since and the cover installed per Jesse's recommendations. I've yet to fire the engine but will be soon. He did also mentioned that he's heard from a few that found the casting of the block is not truly flat but I think that was near the back somewhere.
 
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The engine was all new when I put it together. I cleaned everything with brake clean and blasted everything out with air. It is leaking from the bottom of the cover right about where the AFC is located on the pump. It did not leak at first, it took the engine break in and some laps around a parking lot to get it up to temp until it started. I am pulling the engine out to address another issue and I am going to pull the cover back off and try again. I just wanted to see if there was anything obvious that I did wrong or if it is a bad product
 
My oring did not leak. However the bolts did loosen up over time. I ended up rtving the like mentioned above.
 
You used the correct length bolt in the correct hole right? I've installed two and haven't had any leaks


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As mentioned above I now recommend to use rtv under the bolt heads, otherwise they tend to weep slightly over time. I have had two customers that had a leak from under the cover itself that was due to a small ridge in the block casting that the aluminum edge of the cover got hung up on and didn't allow it to compress the o-ring. All it took was to loosen the mounting bolts and then slide the cover about 1/16" to get off the casting flaw.

There is always the chance that the o-ring got damaged upon installation, there is debris under the o-ring or the o-ring has a defect. If you shoot me a PM with your address I'll drop another o-ring in the mail so that you have one on hand when you pull it.

Jesse
 
I also applied Loc-tite 242 (blue) to the bolt threads upon install of mine this time. Torqued to 18ft. lbs. per Cummins spec as well.
 
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