996 oil leak

[Rise1210]

By the sound of it an oil leak on a 996 is not uncommon.Massive understatement??? I Have just bought one knowing it had a leak now i need to work out where from. It drips off the n/s camcover on the lower corner closest to the bumper straight onto the exhaust. I have read about spark plug tube seals, camcover sealant/gaskets etc but think mine is slightly different as the oil is sitting in puddles on top of the cylinder head????? I bought the car yesterday so haven't had the opportunity to wash it off and take a look so just trying to get an idea of what to look for. I'm a technician myself but work for Volvo so not familiar with Porsche but have a good understanding of engines etc. Are there any oil pipes breather boxes or anything above the engine? Or is it just possible to have oil up top even though gravity usually take oil down from say spark plug seals or cam cover gaskets?

Any ideas greatly appreciated thanks Lee

[logray]

Hi Lee from London!

Well you certainly are on the right track with cleaning the areas and then monitoring.

Yes, the spark plug tube orings can certainly leak and is a simple job to do using a rubber boat plug.

The camshaft covers themselves are sealed by silicone (loctite 5900), and while they can leak if the silicone is very old or wasn't applied properly, the tube seals seem to be more common. Also on both camshaft covers are variocam covers which can leak (1998-2001 have one seal per side, 2002-2005 have 4 orings per side, one per variocam actuator).

On the RH side of the car, there is a crank breather on top of the 4-6 cyl head front of engine that can leak. On same of the car the there is an oil cooler on top of the engine (rear) which it's orings can leak.

On the LH side of the car, there is an air oil seperator which can leak.

On to top of the engine, oil can pool from various sources, AOS and it's various tubes and orings, oil filler tube and it's orings, and oil dipstick and it's orings.

HTH and good luck!

[Rise1210]

Hi and thanks for your reply. I have just read in the service history for the car that 1-3 vario cam solenoid & associated gaskets including plug tube seals were replaced last year also bank 1-3 cam chain tensioner seal & intermediate shaft seal were also replaced at the same time. As the oil leak is on the L/H (N/S) i guess this was an attempt to rectify the problem before. So if this has already been done I'm thinking AOS? will be a suspect. Ive looked at the detailed 'common fixes' and downloaded the PDF . I don't think ill have any troubles replacing it, any idea if its likely to be the unit itself or the pipes to it as i dont want to take the car apart unless i have the right bits to repair. Also how much is this thing??

[logray]

It could be the repairs made previously caused the leak or didn't fix the leak properly. The spark oring seals require some high temp thermal grease otherwise they can leak, the tubes must be fully seated. The cam cover silicone must be applied absolutely correctly otherwise it will leak. The 23 cam cover bolts must also be NEW micro-encapsualted with sealant already on the bolt head base OR they must be cleaned and then a small bead of silicone applied to the base of each bolt otherwise they can leak.

The IMS shaft seal would cause a leak through the bottom of the bell housing.

If you think it is coming from the top I might start by attacking the oil filler tube and crank vent, but again, you have the right idea. Clean the areas and then monitor where the leaks are coming from and attack them one by one.

The AOS itself is about $100 USD, but is a pain in the *** to replace, some say go in from the top, but it is just about as much time and difficulty to drop the transmission and go in from the rear.

[Rise1210]

Logray..... Today i put the car on the ramp washed down the excess oil and checked for leaks. None present at idle and again none present after reving engine to red line and even after holding revs at over 5 grand for longish periods of time. Took car for a short road test 'driving it like i stole it' and back to the workshop to find excessive oil leaking from top of camcover and running down onto exhaust.... After washing down again and monitoring it more precisely ive worked out that no oil leaks at all unless the revs reach at least 5500 and only while driving. Almost certainly leaking from the camcover gasket seems to possibly spray out onto the injector at quite a rate but only if you drive it hard. Washed it down again and drove it home about 15miles not driving over 5000 revs no leaks at all when i arrived totally dry?????? So gonna replace gasket sealant just wondered if this was normal to leak in this way. oil pressure is very good no other faults . Also what sort of a job is this thanks Lee

[logray]

I would be surprised if the leak shows up at 5000 rpm but not at cold idle when oil pressure is just as high. Could just be once it warms up enough???

You're certain (a) leak is coming from the camshaft cover then... Is the leak on the RH or LH side or both? Middle, front of the engine (rear of car) or rear of engine (front of car)? Pictures are great to share!

Anyhow, for the cam cover seal. It's a very tough job to do with the engine in car from what I've read unless you have really small small hands and access to a large selection of quality tools (and a lift/ramp helps tremendously). The engine has to be lowered some which means disconnecting lots of stuff that you need to undo to drop the engine, so why not drop the engine?.. without disconnecting lots of stuff you can only safely lower it a few inches. I've only done this procedure with the engine out of car.

With engine out of the car it's really not all that hard but you must follow procedures precisely (spelled out in the workshop manual).

There are several write-ups on how to do this, but I'll summarize the key points for you.

Camshafts must be locked/held in place with hold down tool before removing camshaft cover.

The 23 cam cover bolts removed and tightened in correct sequence (buy new bolts since they come pre-micro encapsulated to help prevent leaks).

All old sealant cleaned off with paint thinner/acetone.

The bead of sealant must be applied perfectly and according to the WSM, and 1 to 1.5mm in size. Do not use more than that.

You can use "drei bond", loctite 5920, or loctite 5900 as the gasket material (in that order of preference).

Engine retimed/timing checked when done.

If you're going through this trouble to remove a camshaft cover it makes sense to replace things while you're in there (is this a 3.4L?, if so replace the cam to cam timing chain & variocam pads). For either 3.4L or 3.6L spark tubes and orings, oil scavenge pump orings, camshaft end caps, (and for 3.6L new actuator orings).

[Charlesdht]

I have a 2002 C4S with the same problem, at 5000 to 5500 rpm the oil leak drips down on to the exhaust and causes smoke. Did you ever figure out the cause of the leak that was dripping down to the cam cover area? how much of a pain was it to fix? How many labor hours should I expect from a shop?

UPDATE

It was the oil air separator

Edited July 11, 2012 by Charlesdht