Continuously crooked rear main seals
 

I have been having an issue with my Boxster. I bought it in pieces after the previous owner attempted to install a clutch and ended up bending valves. Long story...

At the time of rebuilding the motor I installed a new rear main seal, put the engine back in the car and went about having fun with it. About 2 weeks after getting it up and running I noticed an oil leak and a week later noticed it was getting progressively worse. I was able to narrow it down the back of the engine/bell housing area and proceeded to pull the trans out. I found that the rear main seal was incredibly crooked and the engine was leaking heavily from the back of the crank. I chalked this up to somehow installing the seal wrong, even though I have installed hundreds of rear mains and am familiar with the process, installed a new rear seal and put the car back together.

It has not been about 3 weeks and the oil leak is back same as before. I have not pulled the trans out yet again, but plan to this weekend. I have a feeling I know what I will find.

All that said, has any else had issues with rear mains working themselves crooked and leaking after a couple hundred miles of use? I have never seen this before on another car.

Edit: I have been using Victor Reinz seals. I am going to try an OEM from Porsche next.

One potential issue is that the seal is not seated perfectly. After you pressed the new seal in, make sure it is sitting at the same distance from the crank`s end all around the seal. It`s an obvious thing, so I guess it`s unlikely you didn`t install it properly.

Another thing: the seal originally is not flush with the engine casing, it`s pressed further in by about a mm. I`m not sure if it matters, but may be a good idea to position the lip exactly where it was before.

http://986forum.com/forums/uploads02...1607531550.jpg

If all these all checks out, then another possibility is that the crank got scratched during the rebuild. I hope that`s not the case. Once I had to replace the crankshaft on a different car just because the surface of the shaft had some tiny, barely visible scratches right where the seal`s lip ran...

This problem was written up in Excellence magazine several years ago. A couple of things are absolutely critical:

1. After the old seal is removed, the block and crank areas must be scrupulously cleaned,
2. You should ONLY be using the updated PTFE seal.
3. You cannot even get finger prints on the seal or seal seating areas; Porsche released a special tool to install the PTFE seals without touching them.
4. NO SEALANT OF ANY KIND should be used on the PTFE seal. Install it dry.
5. If you still encounter leaks or seal movement after doing the above, Porsche has a special tool to check the block for concentricity (many early engines were not machined correctly, and this problem cannot be fixed. Porsche used to just replace the engine.)

Good luck with this one........................

It matters more than you might guess; this seal MUST be installed to the correct depth, which is why Porsche released a tool that does this perfectly every time.

Anyone have a part number for that tool? I don't want to pull this out again.

You really don't want to buy the tool unless you do a lot of these, it retails for around $600.

That said, LN Engineering rents the tool, and sells the OEM PTFE seal.

I can`t remember now if I just eyeballed it or I measured the 13 mm distance all the way around based on the manual, but this should be doable properly without the tool:

http://986forum.com/forums/uploads02/seal1607548414.jpg

It certainly helps though to have it, I think the tool you are referring to is called 9699.

Thinking of JFP`s 5. point, it`s unlikely that the cases are deformed, as I assume the seal was not leaking before. Did you split the cases for the rebuild btw? Perhaps they are somehow misaligned?

I did not split the case. I removed the bank 1 head to replace the exhaust valves that were bent.

You need the 9699/2, which has the adaptor for the PTFE seal

https://lnengineering.com/media/cata...s/rs9969_1.jpg

The cases in question are not deformed, they were machined wrong (the opening is not round) causing the seals to leak and pop out.

In that case a properly installed seal should fix it.

Amazing. What happened to the German precision?

Believe me, Porsche is not the only company that cannot always produce round openings in car engines...................

Worse yet, then did produce a $700 tool to prove it.

I don't really know the history of the car, but I can guess based on the residue that was present on the bottom of the motor that it did not have this oil leak before.

The last RMS I put in was a 997 P/N........it was perhaps four years ago. Has there been revisions since then?

The one that was in there (997) popped out a bit after a track day.

The current version is the 0PB-105-249, which replaces the 948-101-212-02, 997-101-212-00, 999-113-476-40, 999-113-490-40, and 999-113-490-41 versions.

Lol, that`s a good one :)

Thank you for this information. It looks like I am way behind.....!

Went at it again today replacing the RMS.

Good: New exhaust makes it much easier as I don't have to take the bumper off
Bad: RMS was crooked again
Good: Subaru RMS install tool is basically a direct fit for the 986
Bad:Oil cooler is leaking
Good: Got the time down from 4.5 hours to 2.5 hrs
Bad: I misinterpreted the service manual and set the seal to 13mm from the case flange not the crank flange
Good: If I have to do it again I can go for 2 hours

We'll see what happens.

Side note: screw that stupid stud on the bottom of the trans. That is the most stupid fastener placement I have run across on a car.