flyboy1717

Yep, another thread to help with an oil leak.

My car has 214k miles on it. The previous owner spent alot of money with a local shop to chase this leak to no avail. I'm now trying to figure it out on my own, with hopefully a little help from my new Rennlist friends.

So the largest leak appears to be coming from the bell housing area. The oil will drip on the exhaust cross over and lightly smoke. After a spirited run, I'm looking at a 4 inch puddle of oil which develops rather quickly. The car only appears to leak after it is run. I've had it up on a lift, and the leak seems to accelerate when the engine is rev'd. Yesterday, I replaced the oil pressure/temperature sending unit o-ring, hoping this was the culprit....it was not. Given the location, I'm starting to think rear main seal. I'm pretty certain this is an engine drop procedure to replace it.

Are there any definitive ways to diagnose it is an RMS failure without pulling the motor?

I am somewhat hesitant to pull the motor, because once its out, I have no way of chasing the leaks.

Some additional information: '92 C2 tip, 214k miles, Mobil 1 15-50 with less than 400 miles on it.

Oil pressure at WOT is slightly over 4 bars (I think it should be pegged at 5)

When the engine is hot, I get the low oil pressure light at idle (this is mildly concerning, though I've read this is common, and acceptable)

I'll likely get it up on the lift again tomorrow to take another look. Any ideas at what to look at while its up there would be greatly appreciated.

Thanks for the feedback.

stevepaa

which side is the leak on or in the middle?

Steve Weiner-Rennsport Systems

Chasing oil leaks requires a methodical, thorough approach to have any chance of success,....

I'd begin the process by cleaning the bottom of the engine, transmission and bellhousing with brake cleaner to get everything as clean as humanly possible. You should get the car on 4 jackstands (very carefully) or a lift since you will run the engine while laying (standing) under the car to spot leaks. Everything must be clean so you spot any moisture beginning to accumulate under the bellhousing where it joins the engine. Sometimes we put a dye into the oil and use a special lamp to make this task easier, but it can be done with the above procedures and some patience.

At 214K miles, I'd not be surprised to see an RMS leak, based on your observations, since gaskets, seals, and O-rings tend to shrink, harden and crack over time and accumulated heat. Since you don't have a clutch disc to worry about, such leaks are more annoying than critical unless the loss rate is high.

Ultimately, the only way to confirm this is by pulling the engine and transmission to separate them, remove the flexplate and look at the seal.

The rule of thumb for oil pressure is 1bar/1K RPM so I wouldn't worry too much unless you run the car hard. High mileage engines sometimes don't have a lot of oil pressure at idle due to bearing wear.

I would suggest creating a fund for an engine rebuild as thats likely in your future.

altarchsa

I have the same problem, EXACTLY as you descrbe. 89 C4, 110K. Pressure same, did the o.p. sender. ?????

flyboy1717

This forum is amazing. Thanks for all the feedback. In less than 30 minutes I had two replies.

The leak is in the dead center of the car. There is a notch/opening in the bell housing which the leak appears to be coming from.

I wouldn't be opposed to pulling the engine to replace the RMS, if I was certain thats what it would be. I understand its about an 8 hour job to drop the engine, so I'd budget 16 for myself (that seems to be the growing trend for me meeting the estimated time estimates). Is there anything thing else that I could check in the vicinity of the area that could be causing the leak. The only thing which makes me question whether its the rear main seal is I believe it should leak fairly consistently at idle and low temp.

I broke alot of the rules of buying a 964. No PPI, no leak down, spotty documentation, however I think the price reflects it. I paid $7500, so I do have a budget to rebuild if necessary. As I stated earlier, the PO spent alot of money with a local shop re-sealing the engine. While the receipt lists the seals, the RMS is not one of them. Part of the $5k job included spark plugs, wires, and a valve adjustment. After giving up on it, the shop decided to refund $2k to the PO because it was still leaking oil. I think I know where not to bring it.

The butt dyno says the car is running great all the way up to 6k RPM's. I think my current plan is to drive it with some oil absorbent pads in the trunk to protect the driveways I need to protect. Come winter time, I'll likely drop it and replace the RMS. Does anyone know of a good DIY article for this job.

Thanks again for the great feedback.

Roger

ian89C4

+ 1 on the RMS leak. You may also check the seal for the power steering pump pulley that is attached to the right camshaft (as you are looking at the engine from the back of the car). It doesn't sound like it, but with these cars you never know.....

There is a great write up on a C4 engine and tranny drop in the 964 DIY section. Just leave out the parts about the torque tube and sleeves and all that stuff, but I am pretty sure that everything else is the same. I have a feeling you are going to get to know you 964 very well here in a few months. It is very rewarding in the end (I had the engine out all winter).

Good luck.

Boeing 717

I did an engine removal write up in the 964 turbo section, should be pretty similar to the normally aspirated model. Its pretty easy, just takes a while.