Help -- 930 case fastener potential problem

[logician]

Hi,

So I realized that in the process of fixing some oil leaks on my 930, I unknowingly removed two case stud nuts, and I'm wondering if this could have caused or exacerbated a leak near the nose bearing.

I realized that I had removed case fasteners today when investigated why my engine still had a leak at the pulley after replacing the pulley seal and the intermediate O-ring. With engine running, the leak appeared to be coming from the case seam in the short length between the main bearing and the intermediate cover. However, it's difficult to tell exactly where the leak was, and it could very easily have been coming only from the very top of the seam, where the nose bearing meets the case halves. I don't think the leak is coming from the pulley seal, as it looks dry (after disassembling engine mount and removing pulley to access seal).

The two nuts that I removed hold the turbo sump bracket to the case, just to the left of the intermediate cover. The two studs run over and under the intermediate cover -- see picture. (At the time, I didn't realize that the sump could be removed by undoing a hose clamp, rather than unbolting the bracket.) Not realizing these were case fasteners, I left the nuts off while I worked on the engine for a period of 2 weeks, until I remounted the bracket. I am uncertain what torque I applied to these bolts when I reassembled everything -- almost certainly too much or too little.

So question: by removing these nuts and improperly torquing them, have I permanently screwed up the seal between the case halves? Or would the leak be fixed simply by retorquing these nuts to the right spec? Or is it unlikely that removing the nuts would have caused this area to leak any more than it was before -- perhaps the problem has always been the dreaded nose bearing leak?

Any help would be greatly appreciated!

-Juan

[Jim Sims]

I will speculate. If the joint surfaces did not pull apart while the nuts were off or loose you will not have a leak. If you didn't excessively overtighten the nuts and move the joint you won't have a leak. However, if there was enough residual stress in the joint when you loosened the nuts or the engine running loads moved things when the nuts were loose you will have likely have a leak. If you overtightened the nuts and moved the joint you will have likely made a leak. Who can tell? I believe your best course of action at this point is to loosen the nuts one at a time and retighten them to the correct torque. If a seam leak remains you'll need to split the case to fix it. Good luck . Jim

[logician]

Hi Jim,

Thanks for your reply:

> I will speculate. If the joint surfaces did not
> pull apart while the nuts were off or loose you
> will not have a leak. If you didn't excessively
> overtighten the nuts and move the joint you
> won't have a leak.

To clarify, I did run the engine (for approximately 30 minutes) with the nuts improperly torqued, and it did leak at the seam between the case halves. So oil has made it's way through the case halves. So I guess the question is whether the case halves might seal again with proper torque on the fasteners, or whether once oil makes it's way between the halves, the case seal is permanently damaged...

-Juan

[Jim Sims]

Once the sealant has broken it will not reseal; tightening the nuts may slow down the leak but only splitting the case and redoing the sealant will completely reseal the joint. Sorry. Jim