964 rear main seal

[JB]

Just completed a complete rebuild on a street use 964 C4. New P's and C's, pauter rods, everything balanced, ext. Crank polished and checked - Std/ std. Jerry woods rod bearings. On start up, everything fine. motor runs smooth, pulls strong. no leaks. good oil pressure. After 10 miles of break-in, stop and check idling motor, no leaks. After 20 miles, return to shop and oil dripping from rear main seal when motor turned off.

Pull motor, pull clutch and flywheel and find oil leaking from rear main seal. A Brown seal was installed from the gasket set. Ordered a new seal directly from Porsche (Black). checked crank sealing surface carefully and looks perfect. Called a friend at local porsche dealership and he says factory procedure is to install dry. Carefully fitted seal to crank without touching sealing surface (per instructions) and pressed flush with case. Started motor and all is well. Ran for approx 10 miles and no leak while stopped and idling. Return to shop and leak is back..

Checked crank case blow by pressure by pulling hose at oil tank. Seems to be positive, especially when reving the motor. Me thinks rings aren't seated causing positive case pressure. Route hose to catch can and go out doing full power pulls for 30 minutes to seat rings. Come back to shop and leak seems less. Rig up pressure gage to breather line and now engine pulls a vacuum when revving.

Reconnected oil breather line to tank and returned to do more full power pulls. Return to shop. no leak while motor is running but 3" diameter pool when motor is stopped.

Any idea what is happening here?

JB

[304065]

Did you install the RMS using the factory tool? How far did you push it in?

Assembling 1966 901/05 Engine- Phase VI- Post-Installation Nits and RMS Change

[JB]

used a similar tool, to evenly press the seal in flush with the case...

[304065]

How much oil pressure? My RMS leaks due to high oil pressure. Did you change main and rod bearings? I imagine you did. Very tight bearing clearance can give you high oil pressure which will blow out of the RMS.

[JB]

yes, new main and rod bearings. Dash gage steady at 4.5 bar at rpm. goes down to 1.5 bar hot at idle.

[JB]

I am considering using a "Speedi Sleeve" made by SKF. Does anyone have any experience with these? The sealing surface on the end of the crank looks OK to me but I'm wondering if the surface finish isn't right after the machine shop polished it or if it is out of round for some reason. Hard to measure installed in the case.

Also, does anyone know if it is possible to remove a C4 transmission without removing the engine? I have removed C2 transmissions numerous times leaving the engine in but not sure if it is possible with the C4 torque tube in place.

Thanks for any help or comments!
JB

[Porshaah]

How do you know it isn't leaking while it's running?
Have you measured case pressure while the engine is stopped and appears to leak?

[JB]

After running it hard for about 10 miles, I stopped in a parking lot and inspected it while idling. Just a slight oil residue and no drips/leak. I did rig up a way to test case pressure by pulling the breather line off the oil tank and inserting a pressure gage pressed into a rubber stopper. It was zero psi when idling and pulls a vacuum when reved up. I did not think to get a reading when the engine is turned off but will do so later today.
Thanks,

[JB]

OK, ran it again until warm. Pulled into shop and left running. Underside of engine dry, no appearant leak. Jacked up car, pulled right rear tire and pulled breather line off oil tank. Inserted a 0-15 psi pressure gage into the line. At idle, it crept up to about 1 psi. Still no leak. When the engine was revved, it pulled down below zero to a vacuum. released back to idle and the gage settled on zero. Still no leak. Turned ignition off and gage stayed on zero. The leak started and formed about a 4" dia circle.

[Porshaah]

I'm not sure how you differentiate oil which likely gets flung around the inside of the flywheel housing by the crankshaft from oil which apparently weeps out of the RMS. I would imagine some of the oil dripping, while the engine is stopped, is oil which has accumalated on the inside of the flywheel housing and is running down and dripping? Is there any oil pressure in the engine while it is stopped?

[AlfonsoR]

Any update on this?

[MBruns]

When you say "installed dry" I assume you mean the outside of the seal to the case and not seal lip to crank, if that's the case it will smoke the seal, it needs lube/grease in the lip area. One other thing I have seen is the small drain back holes in the case behind the seal plugged and the oil leaving the # 1 main brg. has nowhere to go.
Mike Bruns JBRacing.com

[HawgRyder]

I have used the "speedy seal" from Chicago Rawhide it is a very thin sleeve made of stainless I think.
If installed as per instructions...it can extend the life of a crank for a long time.
The old small block chevy's were notorious for "soft" ends...and this solved the problem of grooves in the sealing area.
I also like the CR seals that have more than 1 sealing surface.
For the chev they used to make 2 and 3 lip seals...not sure if they still do.
They also used to make seals that had 1 lip facing each way...(to keep the dirtt out and the pressure in).
Bob

[304065]

Bob, CR is now part of SKF. The SKF "speedi-sleeve" is still available. There is only one seal design offered by SKF-- and interestingly enough, even though the diameter increases 0.5mm with the speedi-sleeve in place, the original dimension seal is used.

[AlfonsoR]

Originally Posted by MBruns

When you say "installed dry" I assume you mean the outside of the seal to the case and not seal lip to crank, if that's the case it will smoke the seal, it needs lube/grease in the lip area. One other thing I have seen is the small drain back holes in the case behind the seal plugged and the oil leaving the # 1 main brg. has nowhere to go.
Mike Bruns JBRacing.com

You might be talking about 2 different types of seals. The conventional seal with a garter spring requires or is recommended to be installed with a coat of oil on the lip that will be touching the crank.

The other type I am less familiar with, it is the one with no garter spring and is supposedly made of some teflon type material. This one is supposedly recommended to be installed dry in regards to the surface to be in contact with the crank. Supposedly applying oil or lubricant on the teflon sealing surface is detrimental to the sealing function for this type of material, so it is recommended to be installed dry. From what I have heard from one mechanic is that if it is installed with oil it will leak. It is also recommended (again, according to same mechanic) to be installed with a special tool and let sit for several hours before running.

I don't know about all that. Not knowing all this before hand, when I installed this spring-less teflon type seal on my BMW 635 rear main, I installed it like I would any common seal, that is to say, I lubricated the "lip". Although this type seal really doesn't have a lip. no special tools, and so far 10k miles later, no leaks.

If I had a choice, I would always go for the conventional type seal. It works!! Some OEMs, BMW anyway, are now selling the spring-less teflon type seal exclusively. If you want the conventional type, you have to go aftermarket.

Other than making sure the drains holes are clear, if you don't want to use a speedy sleeve, you might try to install the seal at a slightly different depth. I installed the rear main seal on my 635 at .062" deeper into the seal housing. Idea being the seal is running on virgin crank surface.

[JB]

OK, here is my update: (long)

I received the speedi-sleeve but could not figure out a way to correctly position it with the crank installed in the motor. There is a flange that is used to drive the sleeve onto the crank. If the sleeve is pressed all of the way onto the crank until it bottoms on the case there are two problems. One is the flange covers the oil return holes and two, the sleeve is still hanging past the mating edge of the crank. If you remove the flange as instructed, now you have no way to push the sleeve further onto the crank to position it correctly without damaging it. The net of it is I did not install the sleeve.

I opted instead to shorten the garter spring about 8mm. I measured the seal ID before and after and it tightened the ID approx. 0.015" - less than the increase in dia fron installing a speedi-sleeve.

I then installed a new from Porsche Black Kaco rear main seal per a Porsche master techs instructions of not touching or lubricating the surface that contacts the crank. I used a very clean installation tool and carefully pressed it flush with the end of the crankcase. Keep in mind that the end of the crank has no visavble grooves and looks perfect.

Reinstalled everything and started the motor - no leaks. Took it out for a 10 mile loop not going over 3500 rpm and very little load. Pulled in the shop and left it running - no visable leak. Let it run for a few minutes while positioning it on a lift. Got under it with a dry blue paper shop towel and wiped the case where it meets the bell housing - got some oil trace. I knew then that there was no fix. I turned it off and it started dripping from the bell housing. Over night it formed about a 12" dia circle.

I pulled the motor again (augggh!) and found oil pooling in the recesses to the right and below the rear main seal as well as from the bottom of the seal itself (and being slung by the flywheel around the bell housing and out various holes).
At this point I am at a loss. I clean the end of the motor and let it sit over the weekend. when I return on Monday, the end of the motor and rear main seal are as dry as a bone.

I decide to see if I can measure how much movement I get from the end of the crank. I fixtured a dial indicator that measures in 0.0001" increments to sit on the top of the crank sealing surface and lifted (pryed) the crank up and down (screwed flywheel bolt in the end of the crank and pushed on that) . To my surprise, it moved 0.005" total. I have 5 other motors in the shop with cranks installed and known not to leak so I measure them as well. They all moved anywhere from 0.0045" to 0.006". Now I am really baffeled.

After much knashing of teeth, I decide that there has to be some internal cause for the leak like maybe a case crack so I dissassembled the motor. I did not mention before that this motor came to me with an oil pump failure. Long story but upon dissassembly, the oil pump pressure side had injested a sheetmetal screw. It broke gears in the pump and broke out the pump housing but there was no other appearant damage internally other than a little bearing scuffing (it was reported to have been started and then shut off 3 times (loud, awful noise) so it was not run long with no oil pressure). I was now wondering if the trauma from the pump failure caused the case to crack somehow. I could see what looked like hairline cracks in the area where the oil was pooling.

So, I cleaned the cases thoroughly and took them to a lab that specialized in penetrant crack detection for the aerospace industry. I went through the process with them but could not find any appearant cracks.

I measured the crank journal dia's and they are very close to upper end tolerance (main journals - 59.989mm, seal journal dia - 89.990mm) and look perfect visually.

Next step is to take crank in to be measured for run-out at the seal journal.
Then I will verify case bore diameters.

What am I missing here? I could install the speedi-sleeve correctly now that the crank is out but am reluctant.

Thanks everyone for the interest and comments. When (and if) I figure this out, I will post my findings.

Jim

[porterdog]

Interested, but got *nothing* for you. Well, I got empathy, for whatever that's worth. Sorry for your stressy hassle.

[AlfonsoR]

I would install the speedy sleeve and install the seal dry on the outside to the case and lubricated with 20W50 on the lip to the crank.

[Porshaah]

What type of instrument was used to measure journal diameters?