Case to Cylinder Oil Leak - Rebuild? Reseal?

tito911s · 06-07-2016, 07:43 AM

About a year and a half ago, I bought a 1984 911 that was a little rough. Was owned by a military guy and sitting outside for a couple years. Hideous fiberglass tail, brakes barely worked and an oil leak on the driver's side over the exhaust.

BEFORE

AFTER

I spent a lot of time sorting the car, replacing front right weal bearing, replacing master cylinder, doing CV joints, adjusting the valves, replacing tach etc. etc. But several weeks ago I finally decided to tackle the oil leak that seemed to be getting worse. I followed the good advice here, adjusted valves and installed RSR seals on the rocker arms with the engine in the car. See my post here.

However, after stitching everything up, confirming no broken head studs, and inspecting the leak further, I have confirmed that the leak is coming from the base of cylinder #3. When the car runs at idle, it seems to leak minimally. However, under load, the thing spits all over the place and has become, really, not fun to drive. Oil dripping everywhere, smoking. You get the point.

I know a lot of guys here have been through this, or other situations that lead to the inevitable "should I reseal" or "do I need to rebuild," which leads to "top end / bottom end rebuild," and all the decisions in between. But I need help. How much longer does it take and cost to do a top end, than say, a reseal? Does it even make sense to focus my attention on cylinder #3, reseal all the gaskets while the long block is out, set the timing on the engine and reinstall?

In short, how would you guys approach and/or budget fixing a leak like this?

I'm not independently wealthy, so backdate/hotrod/rotisserie restore is not on the table.

I look forward to your responses and know full and well that everyone has a different perspective when it comes to what the "best" approach is.

Cheers.

Flat6pac · 06-07-2016, 08:13 AM

If you're so loose that it spits oil, something isn't tight.
If you're pulling the engine, removing a side, treat yourself to a valve job on all 6
12 dilvars studs replaces with factory steel. You lol need a base gasket on #3. No broken studs, the studs can change out with double nuts and maybe some heat eithout removing more cylinders..
The other side of the coin is, you can break a stud, there is rusted nuts on the heat boxes. Intake and exhaust needs to be removed.
Bruce

Discseven · Discseven's Garage

Quote:

Originally Posted by tito911s

...I have confirmed that the leak is coming from the base of cylinder #3. When the car runs at idle, it seems to leak minimally. However, under load, the thing spits all over the place and has become, really, not fun to drive. Oil dripping everywhere, smoking. You get the point.

Tito... by "base," we shall believe you are referring to the point pointed to below---never mind that pic is not of cylinder #3. There are gaskets for cylinder bases and some will even go a step further and apply sealant to cylinder bases. A leak at the cylinder base would require something very odd going on at the base. There is a justifiable school of thought that says that no matter how well an engine is sealed, what matters first is how "clean-clean-clean-clean" the surface is before it's sealed. IF... the prior owner had the engine worked on including the removal of the cylinders and the base matting surfaces were not cleaned well... this could be the cause. In the alternative, the "triangle" is just above #3 with passage for oil to run down between #2 and #3 to the base of #3. And no offense to your conclusion the leaking being at the base of #3---am offering food for thought. Were this the case, it would be the lessor of 2 evils in regard to investment to repair. Maybe the breather hose is cracked / or disconnected? If that were it exclusively... you just saved a good number of dollars. I'd suggest checking that hose and connections before all else.

tito911s · 06-12-2016, 08:15 AM

Quote:

Originally Posted by Discseven

Tito... by "base," we shall believe you are referring to the point pointed to below---never mind that pic is not of cylinder #3. There are gaskets for cylinder bases and some will even go a step further and apply sealant to cylinder bases. A leak at the cylinder base would require something very odd going on at the base. There is a justifiable school of thought that says that no matter how well an engine is sealed, what matters first is how "clean-clean-clean-clean" the surface is before it's sealed. IF... the prior owner had the engine worked on including the removal of the cylinders and the base matting surfaces were not cleaned well... this could be the cause. In the alternative, the "triangle" is just above #3 with passage for oil to run down between #2 and #3 to the base of #3. And no offense to your conclusion the leaking being at the base of #3---am offering food for thought. Were this the case, it would be the lessor of 2 evils in regard to investment to repair. Maybe the breather hose is cracked / or disconnected? If that were it exclusively... you just saved a good number of dollars. I'd suggest checking that hose and connections before all else.

Karl -- everything you are saying makes sense. The engine was rebuilt at some point as there are 946 or 993 triple squared head studs.

As you mentioned, perhaps someone did not get the geometry right, or things weren't clean enough or somehow the copper gasket at the base of cylinder #2 or #3 was not installed right. I've double checked the triangle of death -- and it all looks dry up top. Thanks for double checking to make sure I looked at the easy stuff. I was given some advice to remove the shroud and inspect the through bold o-rings.

I think at this point I'll try to remove the shroud to look back to inspect the through bolts and the top of the engine. Obviously I can't see any of that from below.

I am fairly certain that there will be no way to fix this leak with the engine in. That means I need some help on determining my range of options to fix this leak. Of course, I hope to positively identify the leak. However, if I can't, I will need to determine what engine work needs to be done.

Based on Bruce's sound advice, I would replace all driver's side head studs, do valve job and put things back together. That would be my most inexpensive option, I am sure. Is there any value to doing a compression/leak down test to determine if I need to do more than the minimal?