911SC Oil Leak

yulw · 09:04 PM

Help Please! I have a 1978 911SC with a recently rebuilt engine that is leaking oil onto the heat exchangers and creating smoke. It appears to be leaking oil from between the cylinder head and camshaft housing of the two most forward cylinders (#1 & #6, I believe). I cleaned off all the oil residue and tightened the nuts on the valve covers and have not noticed any leaks from the valve covers. The drip off the backside of the camshaft housing persists, even when the engine is not run for an extended time.

My guess is that the nuts holding the camshaft housing to the clyinder head need to be re-torqued. Any suggestions? Is it possible to remove the lower valve covers and torque the nuts without removing the engine? Is it possible that the leak could be coming from above?

sammyg2 · 10-03-2005, 07:38 PM

If it is leaking oil from the cam tower to head joint, I really doubt re-torquing will do any good at all.
That is a metal to metal joint with a very thin coating of sealant.
If it is actually leaking there you will probably have to take it all apart.
But before doing that, make sure exactly where it is leaking from.
it might just be a leak that can be solved with rocker seals, or maybe even easier.
Spend some time and effort playing sherlock holmes, you don't want to jump to conclusions and solve the wrong problem. In other words, don't fix it three times. If all else fails, pay to have a real expert diagnose it.
Money well spent.

yulw · 10-03-2005, 09:44 PM

Thanks. I already took it to a fancy Euro shop and they told me to replace everything that I just had replaced in a complete teardown and rebuild of the engine and heads from a reputable import shop in a different state.

Do you have any suggestions of other spots to look for a leak higher up above the flywheel? I'll check it out again this weekend.

wilke3169 · 10-04-2005, 07:20 AM

From your description I would agree with Sammy. The rocker shaft seals would be the first place to look. Is the above the flywheel leak another issue? You may want to add a location to your name. May be a Pelican around the corner who can give it a look with you.

sammyg2 · 10-04-2005, 01:48 PM

There are a few common leak sources on top of the motor like the thermostat o-ring, the crankcase breather gasket or hose, and the oil pressure sender. not sure if that's the area you are refering to or not.
One of the problems wth thse engines is the air from the fan blows oil every wich way, making it very difficult to find an oil leak. Maybe the dye and black light trick might help.

yulw · 10-04-2005, 09:50 PM

Location is Norfolk, VA. Any help would be greatly appreciated. The leak is a mystery to me, but I do know that it is dripping off the back of both of the cam towers at the forward most point of the engine (toward the transmission). I do know that there is no accumulation of oil visible from the top of the engine and that a lot of oil can leak out over time. I cleaned off all the oil and dirt accumulation from the underside of the engine and I know that it's not the valve covers. The car spends more time in the garage leaking oil than on the road these days.

What are the rocker seals and where are they located? My original thought was that there was oil in the cam tower that is somehow seeping out, but it could be coming from above somewhere out of sight. It seems odd that it should be leaking oil in the same location on either side of the engine. I'll post a picture on Friday.

sammyg2 · 10-05-2005, 12:54 PM

The rocker arms ride on steel rocker shafts. The shafts are designed to fit snugly in the cam housing and expand to seal when tightened.
Lots of things can cause them to leak, like not being centered, loose in the bore, having the bores scarred or filled with crap, etc.
Lots of us use what is generally called RS seals.
Mostly because i don't think they were installed on any production cars 'cept the RS cars or something like that.
They aren't really o-rings, more like flat rubber washers that fit in the grooves of the rocker shafts. When tightened, the shafts squeaze the seals and they expand to seal against the bores of the housings, no more leaky.
That is what it sounds like you need but I really can't tell from here. My eye-sight isn't what it used to be

Pelican sells em cheeap, but I'd do everythiung I can to make sure that's what you need before going that route. It can be kind of a PITA and it can't be done with the engine in the car except maybe by houdini.

sammyg2 · 10-05-2005, 12:55 PM

IIRC there are also some pressed in plugs near the area you described, little help anyone?

yulw · 10-05-2005, 08:07 PM

I would have imagined that the rocker shafts would be fully contained in the cam tower and not lead to the exterior of the cam tower. I have not disassembled a Porsche engine before...I already paid someone well for that privilege. I'll look it up in my manual tomorrow and take another look under the car. Thanks a lot for your advice!

wilke3169 · 10-06-2005, 02:58 AM

YULW, the two outer ends of the rocker shafts are actually semi exposed. There is no real seal if the oil passes outside of these shafts. Sammy's description of how they seal and suggestion of the RS seals is dead on. If you remove your valve covers you should be able to see and feel the ends of the shafts. This area should be dry upon removal. I assume you mean it is leaking at 3 and 6. 1 is actually closest to your distributor on the left side. You might pick up the rebuild book and have a look. If there is a Barnes and Noble nearby have lunch there and study a copy before you buy.
It's quite possible the problem is elsewhere but this is certainly a location that jumps out from your description. Odd that it is coming from both sides. Like something was omitted during the rebuild.
Good Luck

sandiego · 10-06-2005, 11:59 AM

This may not be your problem but it is a source of leaks. If you fill the oil tank to more than about half way, you can get oil into the air filter housing which will then go out the drain hole in the bottom and on to the engine. Quick check is to see if you have oil in the air filter housing.

yulw · 07:45 PM

I dug out my Haynes manual and I now see the potential for a possible leak from the rocker seals...I get it. However, it's strange that it should be leaking from that high up on the engine if there is a non-stop drip when the engine has not been run for an extended period...we're talking about a puddle here. I would not expect the oil level to be that high. Any insight as to where the oil level should reside in the crankcase when the engine is not running? It's also strange that the outer seals on #3 & #6 are the only ones leaking.

I have had overfilling issues with the oil (I left it in the care of my father who did not heed my warnings when I told him to keep the minimum amount of oil in the engine). I have since drained out some oil, but the leak persists. I'll take a look at the air filter for signs of oil.

Thanks again for the advice. I'll know more on Sun when I have the time to look at it, so stay tuned...

sandiego · 10-11-2005, 03:52 PM

The air filter will not show the oil. But the HOUSING (below the filter) will.

yulw · 10-12-2005, 09:26 PM

I checked the air filter housing and it was dry. I also pulled one of the lower valve covers and it appears that the rocker seals are not leaking. I took pictures and will post them tomorrow. It still look as if it is leaking from between the cam tower and the head.

I also had the pleasure of removing the control pedal assembly for a rebuild this past weekend. What a pain!

afterburn 549 · 10-13-2005, 09:15 AM

if not oil stat or sending unit, I- 4th the motion, rocker seals almost guaranteed!!.....would have to be real sloppy rebuild to get rocker box to leak ...esp both sides......not at a;; likely

yulw · 07:59 PM

wilke3169 · 10-14-2005, 02:57 AM

yulw, i think you need to give the engine a thorough cleaning to get to the root cause of this. I'm sure the real life image gives more clues but, the photos make it difficult with oil everywhere. The powder method and other methods of looking for leaks will work better if you start with less oil in the problem areas.

Good Luck