tracke30m3

My car is leaking oil from where the cylinder (driver's side nearest muffler) meets the crank case from areas marked "A" and "C", leak is strongest from area "A". The other two cylinders on this side also show some very minor oil weeping but nowhere near as bad as this rearmost one. The three cylinders on the passenger side are completely dry.

Leak leaves a spot on concrete floor around 4" in diameter after parking overnight. I've also noticed that on my car "B" is a 10mm hex nut attached to a stud, most other pictures I've seen of 993 cylinders show a hex bolt, did Porsche switch over to a bolt after 1995? I have the same 10mm nut plus stud on the other 5 cylinders.

My guess is the leak is caused either by a faulty cylinder seal ring or a faulty thru bolt bolt o-ring. Car has about 24K+ miles, leak showed up last week after I started using the car after not being used for more than half a year.

One thing noteworthy is that this happened in May of 2010:

https://rennlist.com/forums/993-foru...il-plug-6.html

I bought a complete engine gasket kit and requested that they replace as much of the gaskets and o-rings possible but I'm not sure if the crank case was opened and if the cylinder seal rings and thru bolt o-rings were replaced when they retrieved the missing bolt inside the engine. Engine was bone dry after the engine out job done May of 2010 at around 22K miles on the odo, leak only started last week.

My questions are:

1.) Is it possible that this is somehow caused by the engine out job done in 2010 or is this just another random non-Viton(?) thru bolt o-ring failure? If the new o-rings were damaged during installation I'd assume the cylinders would start leaking immediately instead of 3.5 years / 2k miles later.

2.) Would you guys suggest fixing the leak even if I only use the car once a month or so? I'm worried that dropping the engine to fix this leak will lead to bigger problems.

3.) Do I replace all 6 cylinder seal rings since the L & R side cam towers have to be removed to access the crank case thru bolts.

4.) Do I replace just the leaking(?) thru bolt o-rings on the driver's side only or should I replace the passenger side ones as well? Am I correct to think that it might be better not to touch the passenger side since they're not leaking? Maybe I should only replace all o-rings if the current ones on my car are not the green Viton o-rings?

5.) Is there a sequence I should follow in removing the thru bolts to install new o-rings or can I just remove and replace the thru bolt o-rings one at a time randomly?

Thanks in advance.

Falcondrivr

Mine was leaking in a similar fashion, from the same place. It turned out to be the oring between the heads and the cam tower housing, where the cams go through. Part number 1 in the diagram below.

You have to get the engine down to this to replace:

NP993

Have you verified that the leak isn't originating from the top of the engine? Cylinder base leaks are pretty common on 993's, but they usually don't appear out of nowhere and leave a 4" oil puddle on the floor.

pp000830

I agree with NP993 - you may be seeing some sort of oil line or other easily and inexpensively rectified issue.

tracke30m3

You guys may be on to something, I noticed that if I take the car out to the mall or grocery and stay there for an hour or two the car hardly leaves a drop of oil on the parking lot. But when I get home and leave the car overnight I'll see a 4" oil spot in the morning. This probably means the oil is leaking from somewhere up top and slowly making it's way down, an hour or two isn't enough time for the oil that has leaked to make it's way down but when left overnight the oil eventually makes it's way down.

Falcon, how did you find the leak? Can it be diagnosed with the engine in the car? I'm a bit confused as to how a leak from that o-ring can cause oil to drip from where the cylinder meets the crank case considering that the cams are several inches to the left of the driver's side crank case.

If the leak is from the o-ring (green circle), wouldn't the oil leak from the area behind the yellow arrows instead of somewhere behind the red arrow?

Any other particular places on top of the engine I should check for an oil leak? I'm pretty sure there aren't any oil lines on top of the engine.

I'm outside of the USA and Porsche parts aren't readily available here so I have to cover up all the bases and have the O-rings on hand before I drop the engine to find the leak. I wouldn't want to drop the engine and not have the part I need and have to leave the car in the shop for a month or two while I wait for parts.

tracke30m3

Seem quite dry up on top of the cylinders.

guards red

Hi,

It's most likely a engine through bolt leak. The part you have marked at A & C are a one piece aluminium plate Porsche describe as an air guide. Due to the part being held in place by studs and bolts it's not removable without removing lots of other bits.

Having said that you can remove the air guide plates by doing the following:
1/Remove the oil returns tubes (assuming collapsible ones installed)
2/Thread a nut onto the three studs, lock this with the other nut already on the stud and remove the stud. You can put the later bolts back instead of the studs if you prefer.
3/Remove the air guide.

This will allow you to run the engine and check the through bolt for leaks, or if not that the base of the cylinder. If the through bolt or the cylinder base gasket is leaking as much as you say, you may be looking at splitting the case as the through bolts cannot be removed without removing the barrels...The base gasket cannot be removed without the three on that side coming off either.

If it's the base of the cylinder, you may try VERY carefully slightly loosening and tightening the cylinder head bolts. The risk here is snapping the barrel studs...

I had a similar problem on mine for a period, a change in oil to a thicker grade stopped it and re-seated the through bolt seal. Back to regular oil (Millers 10 50) and its been dry since. But mine was a very tiny leak however.

There is very little on that side of the engine above that area that can leak. The only thing to check is the oil bridge for the chain tensioner. These can been seen in the engine compartment at the far side of each chain cover. They look like this:


Hope that helps.
GR

Mike J

I have another car I am watching with the same issue, but its a minor leak, just a wet engine. We switched brands of oil to see if that makes a bit of difference, since the leak started after a change from long-term changing, and are waiting for initial results. If its the through bolts or base gaskets, then as has been said, its painful since the barrels have to be removed. I agree, there is not much above to leak in this area, and your shots show its dry anyways.

A oil spot of around 4" in diameter after parking overnight is a LOT though - some sealing gaskets/rings have failed, and I doubt if a strategy like brand changing will do much about this.

An issue is that there is a lot of wind action in that area, so sometimes oil can be dispersed and misleading on where its coming from.

The car was sitting for 6 months - have you run the car more since your posting with the same results?

Cheers,

Mike

Falcondrivr

My issue was diagnosed by a very experienced air cooled mechanic. He looked at it on a lift and called it. Somehow the oil runs down to that area from the gap between the head and cam tower housing. When we disassembled it, we could see how it was flowing.
It was a pretty involved job. Needed a cam timing tool from Porsche, and some other "while you're in there" stuff like chain guides and one tensioner was stiff. I went ahead and did a complete reseal of the valve cover gaskets, chain cover gaskets, ect... This was about 20,000 miles ago (~150,000 miles) and my car is still dry.

jo-hans

Mike - what brand are you switching from and to? Viscosity change?

Mike J

He was using Motul 300v 15/50, then ran one year with Mobil 1 15/50, now Brad Penn 20/50. So slightly thicker at the cold end.

Initial results appear to be oil leakage is about 1/2 of what it was with the Mobil 1, measured by oil levels at the dipstick. His oil consumption before the leak was quite low, so we are assuming that remains constant. We may go back to Motul, but he is deferring doing that right now due to high cost (the car is a DD).

Cheers,

Mike

tracke30m3

Mike, yes I've tried using the car a few times more and if anything the leak seems to be getting stronger.

Nice to see you chiming in here since I came to the conclusion that the leak is probably coming from either the thru case bolts or the cylinder base seals from going over (and over and over and over) your thread on Pcar workshop on engine rebuild DIY. I've learned tons from that thread with regards to how the 993 engine is put together. Without your informative posts and clear pictures I'd be totally clueless.

There's just one question I've wanted to ask regarding the DIY, in chaper 10 the picture showing the oil return tubes (4th from last), the cylinders seem to have been installed upside down?

Guards Red, I don't have collapsible oil return tubes so that means removing the air guides without major engine disassembly is out of the question.

Tiger03447

Try using an oil dye and a blacklight...might help some..hopefully it's just a minor leak.