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Leaky RMS? Check this out (Read 1330 times)
porschecidal_maniac
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Leaky RMS? Check this out
Dec 15th, 2013 at 2:00am
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In our shop, we do engine builds, clutches and service of all sorts. The single worst job to have to do twice barring a complete engine swap is a rear main seal. It's not a difficult thing to do, excepting of course that you need to remove the exhaust, transmission, starter, clutch slave, exhaust heat shields, torque tube, clutch fork retainer shaft, reference sensors, grounds from the top of the bell housing, then the bell housing, clutch assembly and flywheel.

All this to replace - or more likely just reseat - a $5 seal.

I would estimate that I have done 30 rear main seals. It's not hundreds, but it's probably about 29 more than most people will ever do and that's only in the past few years.

The last four we did all had a common thread - they all required redos. Just horrible. The work I described above is 16 hours per the Porsche shop manual and even in our shop takes a legitimate 10 hours. What happened?

Well, I finally figured it out. I still order my parts from Ian, as I always have. They still send me a Victor Reinz OEM seal, as they always have. And, the part number remains the same - again, as it always has. The actual seal has changed.

The seal itself has four surfaces. I will call them the outer, inner, top and bottom.

First, is the outer facing surface which faces the outside diameter of seat. The lower part is against the oil pan and the upper part of the outer seal surface is against the top of the block.

The inner part of the seal is the section that grips the crank.

The bottom is the open channel part that contains the spring and faces in when the seal is installed, and

The top is the facing surface that you see when the seal is installed.

The diameter of the seal is the same as it always has been. The spring seems identical to all of those I have ever seen. The difference, in the last few months is that the seal is shorter, from top to bottom by a significant (nearly 3/16") amount.

Instructions in the FSM and from mechanics and technicians and even Porsche itself all state to seat the seal until it is flush mounted with the rear of the oil pan and the rear of the crankcase.

That is how the seal is seated in these photos:





The other thing to notice about this photo is the oil leak below the seal. This is a new seal that was installed into the block with the motor out of the car, before the clutch and with only a couple thousand miles on it. The motor, sadly enough, leaked from the time this car went home until now when we replaced the RMS and seated it properly.

I mentioned earlier I threw out my tool. Let me clarify something. I didn't actually throw it away, I just relocated it to the tool box with SAE stuff in it. My old main seal setter was of the trumpet variety with a conical end and a butted shaft for hammering the seal in. It seated a RMS perfectly flush with the block and, with the old seals, worked perfectly. I wiped the motor off and replaced the seal in the photo below. I used the old RMS tool to set this seal.



Unfortunately, I now know (from costly experience), that this seal, if I were to close this motor up and send Bill on his way that he'd certainly call me up in a day and tell me that there's a puddle of oil in his garage. Well, that won't work.

I went to Home Depot with my new RMS and found what I needed to make my new tool. I bought a threaded inner freeze cap for 4" schedule 30 PVC. It had a square top on it for tightening it into a threaded coupler or pipe end. I used a 3.5" hole saw and cut the entire center out. The inner ring fits exactly in the channel where the seal seats and can be used to tap the seal down into the seat flush to the block.





I simply sit my "new tool" on top of the seal and tap it in until I feel it flush up to the block. Because the seal itself is about 3/16" thinner from top to bottom, accordingly, there is about a 3/16" space from the top of the seal to the outer edge of the seat on the outside. It's a little more difficult, but I think you can make it out from these pictures.







This seal does not leak. I closed the car up with a smile on my face knowing full well that Bill can now focus on finding other crazy things for me to address on his car - none of which will be dime sized spots of oil every place he parks.

  

Jason Gonzalez
944GT & 951GTS
R7 Racing & Restoration & ManiacRacing.net
exclusive.multibriefs.com/author/jason-gonzalez
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