Mystery oil leak questions.

Lyndon302 · 08:10 PM

911 67S 2.0L
A few years ago I did the oil leaks. All pretty good except I can't get rid of a small one on the cam housings. ( No biggie )
Recently it developed a rear main leak. Not bad. Did not really investigate as I planned a rebuild.
Rebuilt engine. Cases in half. Elring made in Italy rear main
Done about 200 miles. Not a drip in my garage. Running really well. Sunday a warm day about 28 and gave it a bit of rev. When I got home I had quite a leak. One would think it would have left a trail up the drive. Which it didn't. I've run it on the hoist and can't see any oil running out. I would think it's a leak like a seal. Its not a weep. Like 2 or 3 inches off oil. Running out of the bell housing and clutch fork compartment. So it's being flicked by the clutch.
The main looks perfect. 😯. Or I should say I can't see oil.
Its in the bottom. Up the left side. If it was the case I would think I would only get a weep. ??
The plug on the left ?? Is this connected to the pressure relief valve ??. Did my high revs open or close something and oil has pressurized this plug and its leaking. ( Or am I just thinking it's an easy fix with some JB weld .
Lyndon

mikedsilva · 12-15-2021, 02:29 AM

Is that definately engine oil? or is it gear oil?
Your seal and case parting line look dry in the photo (unless you wiped it off).

Perhaps your transmission input shaft seal is the leak and you have gear oil making its way into the bellhousing?

Just a thought.

Lyndon302 · 12-15-2021, 04:53 AM

Engine oil. Definitely

T77911S · 12-15-2021, 05:06 AM

put some JB weld on the plugs

mojarra2929 · 12-15-2021, 05:12 AM

How is the death triangle at the top of the engine (oil breather, oil temp sender, etc)? Engine oil might also get in throught the upper opening of the clutch space.

mojarra2929 · 12-15-2021, 05:18 AM

Also check orientation of the gearbox/differential vent or breather. The breather opening must be aiming the front of the car. If not, gearbox oil can go everywhere .

Lyndon302 · 12-15-2021, 03:52 PM

Its has to be the bottom plug. Logic tells me.
Fingers crossed as this would be an easy fix
Lyndon

Reiver · 12-15-2021, 06:00 PM

If the leak was minor and it appears so then that may have fixed it...the main seal looks dry so other than a leak at the case mating surfaces .... as you know the only way to tell is put it all back together and run it.
Unless you have an issue with the main seal directly around the shaft that is throwing oil onto the flywheel without contaminating other areas?
I would change the main seal too if I were you (based upon your leak report) and use sealant around the outer edges while oiling the inner center area.

Crap shoot.

Lyndon302 · 12-15-2021, 08:19 PM

I haven't changed the rear main seal. I have bought an aftermarket seal Vinton seal used here in Australia by a well known supplier.
Its not leaking. All I can do is seal the plug.
If the case was a problem with the 574 then I would think that would be from start up.
Yep I'm looking thru rose coloured glasses but I'm backing what I'm seeing.
About to chuck it back in.
Lyndon

Lyndon302 · 12-15-2021, 08:44 PM

Quote:

Originally Posted by mojarra2929

Also check orientation of the gearbox/differential vent or breather. The breather opening must be aiming the front of the car. If not, gearbox oil can go everywhere .

I have a breather that runs into the engine bay via a filter.

Bill Douglas · 12-15-2021, 10:15 PM

Nice clean orderly looking garage. the car is looking good too.

Other than the oil leak how has the car been going and are you having a good time with it?

florio · 12-16-2021, 12:26 PM

Did you check the oil radiator? Oil can leak down the side and wick into the space between the engine and tranny. Ask me how I know...

Lyndon302 · 12-16-2021, 12:27 PM

Quote:

Originally Posted by florio

Did you check the oil radiator? Oil can leak down the side and wick into the space between the engine and tranny. Ask me how I know...

Yep it's perfect. ( 200 mikes old genuine Porsche )

Lyndon302 · 12-16-2021, 01:05 PM

Quote:

Originally Posted by Bill Douglas

Nice clean orderly looking garage. the car is looking good too.

Other than the oil leak how has the car been going and are you having a good time with it?

Car is great. I'm lucky to have a rust free SWB.
Its lively as it's a -67S engine and weighs 960 kg. Also lucky to have an aluminium case.
But you could not afford this car if you paid for all the repairs and maintenance.
Lyndon

MBEngineering · 12-17-2021, 08:50 AM

HI Lyndon

the flywheel oil seal looks to far in and could be part blocking off the hole for the rear main oil return into the crankcase, making the oil pressure to build behind the seal and leaking past

only a poss' , or maybe one of the plugs in the back of the crank, only the flywheel is dry?

Lyndon302 · 12-17-2021, 11:44 AM

Quote:

Originally Posted by MBEngineering

HI Lyndon

the flywheel oil seal looks to far in and could be part blocking off the hole for the rear main oil return into the crankcase, making the oil pressure to build behind the seal and leaking past

only a poss' , or maybe one of the plugs in the back of the crank, only the flywheel is dry?

The flywheel is dry.
The outer of the pressure plate is damp. Thus flinging out the clutch fork window.
The seal is 100 percent dry. Does anyone have a pic of the drain hole. This is of interest
Lyndon

proporsche · proporsche's Garage

the holes are what i remember way back towards the 1st bearing you are ok on that one.But..looking at the case somebody used hammer and chisel in the past,it is pretty banged up...Hopefully it is not on the outside where the seal slides in.But if it would be leaking there it would most likely splash around...
I also think that the culprit was the bottom plug..lets see cross fingers..

Ivan

Lyndon302 · 12-17-2021, 12:41 PM

Quote:

Originally Posted by proporsche

the holes are what i remember way back towards the 1st bearing you are ok on that one.But..looking at the case somebody used hammer and chisel in the past,it is pretty banged up...Hopefully it is not on the outside where the seal slides in.But if it would be leaking there it would most likely splash around...
I also think that the culprit was the bottom plug..lets see cross fingers..

Ivan

Thanks. I will leave it as it is. The engine is in but only the four mount bolts. I had a busy day Friday and didn't get the hrs I needed to finish it.
The case to seal is fine. I used some Curil T on it. I can't put my hand up on the damage but.

Lyndon302 · 12-17-2021, 12:46 PM

Just to be clear. This was a leak of about 4 to 5 table spoons. You would expect it to be running not dripping. I was expecting the seal to be cocked or ripped. Eg a proper failure.
I'm thinking I will take it out and replace the seal now. Its only a few hrs work at this point and I have a viton seal in hand.
Should the seal be flush with the case ?
Lyndon

proporsche · proporsche's Garage

i usually have it flush but again yours is a little deep but not blocking the holes..look 66 case
https://bringatrailer.com/listing/porsche-911-crankcase-and-engine-parts/