Sealing bottom cover bolts

Thoughts: the stock grade-zero 1/4-20 SAE bolts are amazingly weak but need careful torquing (don't have the value handy but it's in inch-pounds), and the front & rear pairs of bolts are 5/16-18 SAE needing slightly MORE torque. Second, if you coat the block-only with RTV silicone before adding the gaskets, it's easier to remove the pan or gasket without it cementing itself to the metal. Third, the thin steel pan rails are VERY easy to bend, which pinches the gaskets in pieces with over-torque (just before a bolt snaps off). Be SURE the pan rails are flat without waves. The rails can be straightened blacksmith-style with a hammer & vise-grip pliers plus a thick strip of steel, & you'll be startled to find how easily they bend. Cork pan gaskets in some rebuild kits are easier to crush in pieces than the 'composite' gasket types. I've also seen steel rocker cover leaks that ran down the block so some think the pan is leaking (same gasket problems).

I sympathise- it's a real problem to get stock OR aftermarket pans (or rocker covers) to seal off completely. And even the best job doesn't last long with a bent rail....

Since it's leaking through the bolt holes and not around the edges of the cover, why not try crush washers or the kind of sealing washers that have o-rings around the ID?

On the ZF, the lower cover leaks mostly because the bolts loosen up slightly. I use studs, good washers & elastomeric self-locking nuts, with a tiny o-ring around each stud between the cover & case, since I've found leaks that go under the cover only halfway to the stud (or bolt), then lube travels down the stud (or bolt) to leak at the cover/bolt-head interface, which is often irregular. The cover needs a little chamfer in each hole to accommodate an o-ring.

Haven't tried them but there are washers for stock bolts with rubber inserts bonded to them to accomplish the same thing. Some use these bonded washes on the rear case cover, too.

[QUOTE]Originally posted by LF - TP 2511:
Despite the work being done by the foremost ZF vendor, my ZF manages to weep oil from around the bottom cover bolts. Noticed this with it on an engine stand with totally cold oil. Hate to think what happens when oil is warm.

I'm thinking removal of the cover bolts - NOT the long, cross bolts - and covering them with a suitable sealant might stop the drips.
That worked for me on a similar leak, a little RTV around the bolt head and re tighten.

I had a similar issue with my ZF after Quella rebuilt it.

I contacted him regarding the weeping of oil from bottom cover bolts and he asked that I bring the ZF back so he could take care of the issue for me free of charge.

I had no desire to remove the ZF from my car and take another 610 mile round trip to his shop after just getting it installed.

Mr. Quella recommended that I pull each bolt individually, clean them with brake fluid (along with the bolt hole area), and reinstall them using RTV near the bolt head.

This seemed to take care of the issue.

Devin