Brand new rear main flywheel seal leaking under acceleration!!!

Dana_Drury · 05-26-2002, 03:51 PM

Hi Guys,

Well when I thought it was all over and complete...

Finally finished off most of the work, was taking it for a test drive and noticed that white oil smoke was coming out after about 10 minutes of driving.

This is the second time the car has been driven and it has been started numerous times over the last few weeks. Pulling over and checking under the car, it seems that the rear main is leaking, but its brand new.

We are pulling the engine out again , but can anyone give me some suggestions as to what may have caused it. Theres not a drip under low pressure if your slowly driving around, but give the car a bit of acceleration, and whammo! it starts to leak heavily.

Could the fly wheel have been over tightened, or the bolts not installed in the correct order to cause this? Or could the seal simply be faulty. There is not a drop of oil from anywhere else in the system.

Oil pressure was fine (1 for every 1K of revs roughly).

john walker's workshop · 05-26-2002, 04:07 PM

you don't say what year it is, but i've seen 2.7s that had such a worn out mainline that you could move the flywheel end of the crank back and forth 10mm. needless to say, there's no seal that would work in that situation. when you get it out, walk the flywheel side to side with a couple of screwdrivers on each side. flywheel seals are not normally leakers, even pretty old ones. are you sure it's not the oil cooler, or something on top of the engine running down?

Dana_Drury · 05-26-2002, 06:08 PM

Hi John,

Excuse me, I should have posted the year, its a 1977 3.0l Carrera. I assumed that it was the fly wheel simply because that and the clutch was the main thing we replaced.

I will try what was suggested. I can't imagine what would have been affected at the top of the engine to cause that much oil to come squirting out other than the fly wheel.

I guess I will know a lot more once the engine is back out.

The fly wheel installed fine, and there didn't seem to be much room for it to move. When I had the PPI done, the mechanic said the Rear main was leaking and should be replaced which is why I have done it (but I didn't see much of a leak.

Thanks for the reply.

Jim Sims · 05-26-2002, 06:27 PM

Five weeks ago I replaced a rear main seal in a 2.7; it wasn't leaking, I just replaced it since I had the flywheel off. The car has been running for about 5 weeks and 600 miles now with no leaks. I used a slide hammer method to extract the old seal that doesn't leave marks on the bore or crankshaft and the Porsche rear main seal installer tool to put the new one in place. In addition to the main bearing caused runout problem John Walker refers to, there is the possibility of the portion of the crankshaft that the seal rubs on being scored or worn. This can also result in too much runout or roughness for a new to seal to follow or withstand and it begins leaking soon after installation. Besides a new crank there are several options to fix this: 1) place the new seal in a slightly different axial position so it rubs on an undamaged portion of the crankshaft, 2) grind the scored portion of the crankshaft down to the next standard size and use an oversize seal (Porsche lists such a seal in their parts), 3) install a CR Speedi-sleeve over the scored section of the crankshaft and use a new standard size seal. In option 2) there is the likelihood of grinding through the surface hardening which means the new sealing surface will be soft and have reduced wearing life against the new rubber seal. The crank can be rehardened but apparently this can cause warping and require all the running surfaces of the crank to be reground. The option 3) CR Speedi-sleeves (they come with the required installation tool) can be installed with the crankshaft in place in the engine but may require a slight increase (.010 " on the diameter) in the mating flywheel counter bore. Cheers, Jim

Jim T · 05-26-2002, 06:38 PM

Are you using the brown and black seal?

Jim Sims · 06:44 PM

I had my 2.7 engine out looking for oil leaks and it sure looked like a rear main seal leak while the engine was in the car but it wasn't. It was a top side leak; most likely an old hard breather hose that wasn't sealing well to the nozzle on the breather cover. I changed all the possible topside "oil leakers" while I had the engine out: breather cover gasket, breather hose, oil pressure switch, engine mounted oil thermostat o-ring and engine mounted oil cooler seals. The breather hose is the only thing that cost very much. One last thought prompted by the leaking under acceleration statement: is there any chance the leaking oil is coming from the rubber drain valve (sort of like a "duckbill" valve) that drains a line that comes from either the air cleaner housing or air box? It is mounted on the passenger side up on the sheet metal near the starter. If for some reason there was too much oil in the system it can find its way out through this drain valve. I'd sure check this valve and then address a possible high oil level before pulling the engine. Cheers, Jim

GB83SC · 05-26-2002, 06:45 PM

Did you change the oil pressure swith and the oil thermostat o ring when the engine was out? if not that could be the problem. with the engine off stick your finger in the base where the trany and engine meet if it is the flywheel seal you will feel the oil in there.

Dana_Drury · 05-26-2002, 07:30 PM

The new seal installed as a dark brown one part no 999 1113 05752.

The original seal was only leaking slightly.

I didn't replace the Thermostat O-Ring etc, but I have a new ring coming over today so I will replace that in the mean time. The rest of the engine seemed fine as far as oil leaks were concerned, the oil return tubes are fairly new and there are no oil leaks there.

I will look into the other possibilities. Hopefully it isn't the fly wheel seal and its leaking from some place else but the oil was dripping down from that area and dripping onto the exhaust pipe that runs just under where the transmission and engine mate.

The car has only done 113,000 KM so I didn't think there was enough milage there (70,000ish miles) to score the crank case.

I was surprised that it leaked after 20 minutes of driving after a few quick bursts of speed, yet when we stopped for a few minutes and I had to drive the car into the workshop there wasn't a drop of oil.

I suspected the Rear main because we just replaced it, but it could oil over filled (10 litres), Mobil 1 (5-50w) though I thought 10 litres was correct (it has an external oil cooler).

I have to replaced the internal thermostat now it seems as the car is overheating, the internal oil cooler is not getting hot. So I will get in there and have a look at the rings.