28gts

Yes, a thicker viscosity oil does help with oil leaks.
Generally, though, the engine should be leak free with a either oil.

cobalt

I won't anything less than 15w-50 personally. I find running thinner oil will leak more than not. I have not had issues and have been using it in my 911's since the 80's. Did the OP verify his torque spec is correct and double check the case bolts? Any signs of oil making a path from someplace else? I find it is usually from another place than the bottom of the case. Also I would never touch a mating machined surface with a scotch bright pad or anything abrasive. Red or green IMO are too abrasive. Use a chemical to strip the old sealant off, or a plastic tool. If anything some very fine crocus cloth will do the job without any chance of scratching the surface. Also did you spread the 541 or just apply a bead? Spreading it with an acid. brush is usually fool proof.

GL one drip every 20 min of running time is a fair amount.

DonD964

Hi Thanks again for the feedback. I don't disagree that thicker oil would slow down the leak, but yet to see it stop leaks unless your experience is different.

As for it dripping down from another location, you have me second guessing myself now....I will check it again

I did lay a bead of locktite 574 as opposed to spreading it, as that was the initial recommendation I received but at this point I'm willing to try anything!
Thank you!

No_snivelling

Granted my experience with mating engine cases is limited to motorcycles, but I was taught always to lay a very small bead of sealant and then spread it into a thin layer.
The reasoning behind this is that you don't want the excess sealant to be squeezed into the engine where it could later break off in chunks that could block oil passageways.

cobalt

Actually once the 574 touches metal and air is displaced it begins to harden. So if you lay a bead and are slow at tightening everything down the possibility of a leak by keeping the case halves slightly separated increases. Just like when you mount the cam towers if you don't work quickly and have a bead of 574 instead of a thin brushed area it can cause binding of the cams by not allowing you to tighten the nuts properly and make it flush. Porsche uses 574 because it is unlikely to do damage if anything makes it into the case. They do say do not use a silicone sealant as the strands might break off and clog the oil pump. However I opened a factory sealed 996 Cup car engine that had never been opened and it was full of silicone sealant.

Black_Hat

I remember this thread on pelican:

https://forums.pelicanparts.com/911-...r-rebuild.html

there is a solution using a vacuum, "Apply some LocTite 574 (or similar) to the leaking area and watch it get sucked in"

disclaimer- I've never used this method.

the thread goes over other possible leaks but the subject of the thread is a 964 case leak after re-build

Stefan

Gus

Another option is to install a one way check valve in the main crankcase vent hose. The check valve allows positive pressure out, and creates a negative pressure within the crankcase. The negative pressure will reduce the crankcase internal pressure which should reduce the oil leak. I have installed and my minor oil seeps have stopped

J richard

Something is off about the case through bolt directly above the leak. I’m used to seeing at least 3-4mm of thread out of the end of the nut.
is the bolt too short and you don’t (didn’t) have sufficient torque on that bolt? Is the oil coming thru the flange around the bolt? I hate the suggestion but pulling that bolt using some grey Rv on the shaft of a proper length, shouldered bolt torqued to spec would be my next try. You could leave the bolt out overnight to see if the drip increases, and check the seat surface of the bolt holes for burrs/gouges. The 574 should have sealed the mating surface of the case but the bolt bore is the narrow spot particularly if you just ran a bead on the outside of the bolt hole…

cobalt

Interesting observation. I would of course check all bolts for torque again. However the factory bolt does look like this. It is hard to see but It looks like you aren't using factory hardware and I don't see any markings other than SJ and the rest I can't zoom in on. Is it standard SAE thread non hardened? It should be an 8.8 bolt if it isn't it is possible it has stretched or the cause of the problem. I have to verify I believe the nuts are non nyloc locking design. They would need threads to go beyond the end of the bolt to work properly.

Pic of factory bolt.

DonD964

Thanks Cobalt ...this could definitely could be my problem.
When I pulled the engine out there was no bolt in there at all. I think this bolt might also hold a support bracket for the splash pan and I forgot about that.
When I bolted the engine cases back together, I never replaced that bolt which means your theory would be correct. I applied the locktite 574, never inserted a bolt into that hole then after the fact when I noticed the leak I tried to insert another bolt I just happened have on hand which is NOT hardened and that could be why it is still leaking.

Regarding application of a thin layer versus a bead, I might try that next time as another rennlister suggested the same thing. I really appreciate your help.

Does this mean a whole new teardown if the Loctite didn't take? I hate to use shortcuts but in & out with this engine is getting old.
Thanks,
Don

cobalt

Yes that is one of the 2 nuts that need to be removed to remove the lower heat shield bracket. Per the manuals they say to remove the bracket when lowering the engine. I would consider replacing the bolt with one of proper length and torquing it down. You might consider although I don't always say to try this but in your case might be worth a slightly higher torque and see if it slows down the leak. If it doesn't make a change I would try this vacuum method. I have never heard of it but I always say try the least invasive approach first. You never know.

GL I always hate when these little things can turn into a major PITA. I hope this helps and you are set without any major setbacks.

DonD964

Thanks again and another good suggestion! I always appreciate words of encouragement.
Don

DonD964

Gus thanks that does sound like another great suggestion. I have seen those....anything is better than pulling & tearing down the engine again!
Don

DonD964

Gus do you or does anybody know of another source for a check valve? What is so magical that it cost over $400.00???

s65e90

Maybe something like this....


One Way Check Valves, Piston Style - Vibrant Performance