Stripped threads on rear main bearing cap
 

Working on sealing up my engine after installing a new rear main seal, I installed the oil pan only to discover that the threads for the oil pan bolts in the aluminum bearing cap are pretty stripped. They will hold a bit of torque, but not enough for my comfort.

Looking through my disassembly photos, I see that the metal there is pretty thin and open directly to the crankcase. (i. e. no drilling/helicoils)

https://cimg9.ibsrv.net/gimg/www.for...9aa94e63f7.jpg

I was hoping it was a little deeper and longer bolts might be able to grab some decent threads.

Aside from disassembling everything again (Ug! Would add a week+ to this project, waiting for replacement gaskets, etc), any ideas on making sure this area stays sealed?

~Steve

That is a MAJOR bummer. Visit your local machine shop guy and see if he has any suggestions.

I don't see why a helicoil wouldn't work. It's either that or tap to the next size and use larger studs. Or replace the retainer. Studs should be used in those two holes.

My experience with helicoils is all secondhand--but I was under the impression that the holes needed to be drilled out before the helicoil could be installed (and everything pulled out to do it.)

~Steve

Just about any way you do it will require drilling or disassembly. You will need to remove the oil pan at least. You should be able to do it if you're careful. Remove all of the chips you can before you put it back together.

Another thing, you shouldn't torque oil pan bolts. Watch the gasket as you tighten it. You will see the gasket squish out slightly when it is tight enough. Use studs on the seal reatainer, like original. If you can get those nuts that tight, it will be fine. Use thread sealer on the studs, in the seal retainer.

Sorry, I misunderstood the issue. On hand are many seal retainers. I can get one to you for not much, and within 3 days via priority mail. Mike

Thanks. The manual calls for something like 10-12 ft/lbs or something equally ridiculous like that. My torque wrench doesn't even go that low. I used a 1/4 drive socket and proceeded as you outlined. The bolts on the retainer are almost, but not quite, as tight as the rest.

I'm going to take my chances with the assembly as it is, knowing that I can still redo the whole thing with the engine back in the truck. The only real risk is a little oil on the clutch, which would suck, but I suspect I'll have weeping, if anything, and not the flood of oil I was seeing before.

If I do need to re-do it, I'd pull the whole retainer and do the drilling on the bench to avoid any chance of contamination.

~Steve

Make sure you put sealant on the studs/bolts on the retainer as since they go thru they themselves can be a source of a weepage.

Good call--hadn't thought of that.

Do you, btw, happen to know the recommended torque for these? Couldn't find it in the manual.

~Steve

Tap it to the next larger size.

Put in bigger bolts.

Sorry Steve I don't. I just tighten them 'snuggly'.

I remember back a ways that someone installed metric studs/bolts. Don't remember what size but it was just slightly larger than the striped hole but smaller than the next SAE size. May hold you over until you have to drop the pan again.:-hair

Good luck.

The engine gods apparently want me to pull that pan off.

Snapped a bolt deep inside the timing cover while torquing the bolts down. Gotta pull the pan to get the cover off and fish out the broken end, so looks like I'll have an "opportunity" to drill the retainer and tap for studs.

~Steve

You don't have to remove the pan for the timing cover. A timing cover kit includes the front portion of pan gasket.

Assuming you are using the correct length bolts and torquing them properly, you should replace all of those bolts because they will not snap if all is well. If one failed, then the rest may follow.

Some of the timing cover bolts will contact the cylinder if they are too long. This can result in improperly torqued bolts and possibly severe engine damage. You should be able to thread them all the way in by hand and then torque them. If more than hand strength is required to thread them, find out why.
Use thread sealer on the bolts that go through to the water jacket. Do not use RTV for this purpose.

Well, now that I have two reasons to pull the pan, I think it's worthwhile. Nice to know for future reference, though.

I first thought that my torque wrench had gone south on me, but in testing it yesterday, it seems fine. I'll pick up some new replacements today.

I was not aware the bolts went through that far! I'll check out the thread sealer and clean up the threads as well.

Many thanks for the tips.

~Steve

In the end, this was the only way to get the pan tightened up. I tried to clean up the old threads, but there wasn't enough metal left to make that work. I drilled out the holes and tapped them for 3/8" coarse threads, then installed 1" studs. I had to drill out the holes in the pan, too, of course, and be very careful installing the gasket so it didn't rip. It's still possible to get a socket on the bigger nuts, as they stand proud of the pan lip a bit, but any larger would be a problem.

I noted, though, when I pulled the pan off, that the pan to retainer seal was weak, so glad I took the time to fix this.

~Steve