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Join Date: Aug 2004
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Angry Trick to gettings seals to seal?

After a couple of weeks of driving, my 73S 2.4 has developed a couple of small leaks. I won't know for sure until I pull the engine again, but one appears to be from the pulley seal, and the other from the flywheel seal. Everything else seems pretty oil-tight.

Are there any tricks to getting these seals to seal? I followed the basic procedures and both went in without any drama, so what's up? As an additional note, my 120k miles engine was previously leaking (draining is a better word) everywhere, and most of the seals and hoses were crumbling piles of ash - but both of these seals were in good shape...as if they (alone) had been somewhat recently replaced?

Do these seals always leak or are they at least chronic leakers? Am I facing a losing battle, so I should just live with the drips? For reference, after 20 minutes of spirited driving down the canyon, and with the engine up to full temp, the flywhee seal will leak, oh, a dozen or so drips over the course of an eight hour day in the parking lot. The pulley seal will leak maybe four or five. Is this as good as I am likely to get? I don't relish pulling the engine again, but it's only a two-hour job each way, and I still have the borrowed hoist and stand/yoke, so it's not insurmountable.

Thanks,
Brian

73 911S Targa
Signal Yellow "Lemondrop"
This car rocks
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Old 10-05-2004, 06:28 AM
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I don't have answer for you, but I'm wondering what the deal is with all the leaks people are having. I'm building my engine now and all of you guys have me concerned. I've never had a leak after building a japanese car or motorcycle engine. What could the difference be?
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Old 10-05-2004, 08:23 AM
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On the rear main seal does anyone think it would be advisable to use loctite liquid gasket around the RMS?
Old 10-06-2004, 12:25 AM
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Curil-t is a good choice around the crank seals. I know it is what Wayne recommends. I feel your pain. I've had to replace the FMS twice on one engine before I got it right.

Good luck,

JP
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Old 10-06-2004, 06:04 AM
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1. Pull it.

2. A sealant is unlikely to help here. You likely have a leak on the shaft, not on the case itself. Check the case for ovality, if you squeeze the seal to make it oval when it is installed it WILL leak (trust me I know). Make sure the shaft does not have any wear in the old seal area. If it does look at speedi-sleeves, moving your seal slightly forward, or go to the undersized seal.

3. You should also use Curil-T on all the paper gaskets before you instal them. Sorry, but if you have leaks on paper gaskets now it is too late.

4. Hope it is not this....

Rear Main Seal Hell
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Last edited by Porsche_monkey; 10-06-2004 at 09:49 AM..
Old 10-06-2004, 09:47 AM
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I had my RMS leak. The fourth time we got it to seat on the crank shaft in an area which wasn't worn. It doesn't leak now. However I have some leaks on the Intermediate shaft gasket.

I'm thinking of using a silicone sealer to create a bead on both sides of the gasket and then re-installing.

Anyone try this?

Tristan
Old 10-07-2004, 01:25 PM
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Quote:
Originally posted by Ho Hum 74

I'm thinking of using a silicone sealer to create a bead on both sides of the gasket and then re-installing.

Anyone try this?

Tristan
I don't understand...
Old 10-07-2004, 01:37 PM
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Get a high temp silicone (black like the one in Wayne's book). Then cut the nozzle at an angle to provide a small thin bead. Run this bead around the entire gasket perimeter. Wait for it to dry, then do the other side. Then install.

You can now buy valve cover seals that have this bead already imbedded in the manufacturing process.

Tristan
Old 10-07-2004, 01:40 PM
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But your seal leaked on the moving seal, not the fixed portion didn't it?
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Old 10-07-2004, 01:41 PM
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Hold on. Not sure we're talking about the same seal. I'm talking about the intermediate shaft cover seal. Plain old gasket. Not the flywheel seal. That I had to re-install on a better place on the crank as my crank had a small groove in it which passed 3 inspections!!

T
Old 10-07-2004, 01:43 PM
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Sorry. I used a sealant there the second time. No leaks thereafter.
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Old 10-07-2004, 01:45 PM
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OK! So we're on the same page. I'll try this as well.

T
Old 10-07-2004, 01:47 PM
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Oooo, oooo, something I am very educated with:
Lip seals are designed with either sealant or a very thin rubber seal on the outside diameter. The 911 rear main seal does not have asealant but has rubber about half way ou. this makes it seal but also makes it easier to install.
They seal very well unless the bore is out of round, has sharp burrs or edges that rip the rubber, is oversized, or if the seal was installed incorrectly (cocked or hammered).
It is very important to push the seal in square and not cock it or dent it.

Single lip seals are designed to only keep stuff in. They do this by a thin rubber lip rubbing on the shaft. if well lubricated they seal well, if dry they burn and don't seal. over time the rubber lip wears as does the shaft where the rubber lip contacts it. You've all heard people talking about seals drying up if the engine sat too long without running, IMO that is because the lip of the seals lost all lubrication over time and burn up before the lubrication is re-established.

Always use a compatible grease on the inside diameter when installing a lip seal. Do not use a sealant on the outside unless you are trying to compensate for a bore that is damaged or out-of-round or over-sized.
In those cases a sealant may make up for the mechanical short coming.

Double lip seals are designed to keep stuff in, and to a lesser extent
keep stuff out. With these, lubricant is even more critical because the outer lip will not see oil, but will trap dirt if it gets burned and has clearance.
The condition of the shaft is very important. Lip seals by nature will cut a shaft over time unless it is of a very hard material (over 500 BH).
If the shaft is cut, you can compensate by placing some sort of shim or gasket material behind the seal so that it does not go in as far therby making it rub on a different and undamaged part of the shaft.
Excessive diametrical movement in the shaft will also cause a leak, but if a 911 engine has enough crankshaft displacement to cause a seal leak, you have bigger problems than oil.
Old 10-09-2004, 06:33 PM
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OK - thanks, everyone.

I will be pulling the engine again in a couple of weeks, and will see what I can learn - whether it's leaking around the seal or around the shaft, and if the shaft or case are damaged or out of round. I suspect that I damaged the seals when installing them because (a) I didn't grease them well, and may not have greased the inner bore at all, and (b) I more or less hammered them in place using various instruments, and they passed through various cocked orientations en route to their final placements.

Yes I know that was stupid, but I'm learning as I go. If I didn't want to learn, I would have just written a friggin' check. Now I can add "installing seals" to "pulling/reinstalling the engine", "timing the cam" and "checking valve clearances" as things that I'm getting LOTS of practice on. :-) But trust me, nothing is as bad as fishing a long-dead mouse from deep within a (my wife's) Range Rover's AC duct system.

So - I'll see where my seals are leaking, check the shaft and bore, grease the inner diameter very well, perhaps add sealant to the outside, and carefully push them straight on using a section of pipe or something similar.

Everyone cross your fingers for me!!!!

Thanks,
Brian
73 911S "Lemondrop"
Signal Yellow Targa
Livermore, CA
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Old 10-09-2004, 08:51 PM
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Hi Brian,

Small leaks are the biggest pain in the A**. Attached are photos I took on the RMS assembly, two of which I think may be useful for you. I cleaned the inside area so that all the surface was bare metal (and minor edge deburr) and installed the seal using a press in order to have alignment. Does it leak? Don't know yet.
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Old 10-10-2004, 05:57 AM
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Keep chipping away! Good luck.

Tristan
Old 10-10-2004, 06:07 AM
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