Oil Cooler Seals question

thetorch · 10-29-2022, 12:21 PM

I know there are threads on this, but I have bought 3 different seals (1 red 2 green) and why on earth is the lower seal on the oil cooler 1mm less tall than the top 2 smaller ones? That can't be by design, no?

No wonder I keep having a seeping oil issue from the bottom one.

Should I use the new green one I have (middle one)? Use some curil T?

left: top seal green FPM type: 9.86mm tall
middle: new bottom seal, green FPM type: 8.82mm
right: new bottom seal, elring red: 8.54mm

I really don't want to redo this a 4th time.

thetorch · 10-29-2022, 02:56 PM

welp, the recess looks to be about 1mm less in the lower seal, so it must be by design.

Suggestions about using a new green seal vs a new green seal with Curil-T are welcome.

stownsen914 · 10-30-2022, 05:55 AM

I believe I've heard that this has been a common issue, and that some manufacturers seals are better than others for this application. Hopefully someone will chime in with specifics.

Uwon · Uwon's Garage

You may want to have a look at the first portion of Post #344 in my build thread…
Evolution of a Carrera RST
It’s another possible source for that darn oil cooler leak.
Hope this may help.
Johan

thetorch · 10-30-2022, 01:03 PM

Quote:

Originally Posted by Uwon

You may want to have a look at the first portion of Post #344 in my build thread…
Evolution of a Carrera RST
It’s another possible source for that darn oil cooler leak.
Hope this may help.
Johan

Thanks for the suggestion. I installed it on the engine stand during the rebuild with nothing that could interfere: no shroud, no cooler duct, no intake, no ITBs, no linkages, no tins. Nothing.

I think I am going to have to have another go with a green seal.

Zuffenwerker · 10-30-2022, 02:11 PM

Very common for that bottom seal to seep oil. I always install them using a silicon grease to keep from pinching but have had troubles with seepage. Never tried a sealant because your not supposed to have to put anything on it other than lube.

Make sure your cast in steel pipe behind the cooler is sealed up and not the cause of your leak. If it isn’t sealed up it will trick you and make you think its your oil cooler seal. There is a tech bulletin from Porsche on this # 89-11. I can post a picture if you are not familiar

regnihe · 10-30-2022, 05:46 PM

I fought this for a year. Different seals, RTV, all kinds of tricks. We finally pulled the cooler and had it pressure tested. The cooler was leaking.

thetorch · 10-31-2022, 05:27 AM

I am certain it's coming from the seal. 100% dry everywhere else. I did the service repair on the pipe / thin case a year ago.

I just put the new green seal with Molykote Dow 111 grease only, and seemed noticeably more proud than the red one. Got good squish this time.

I am hopeful.

thetorch · 10-31-2022, 05:29 AM

Pic for reference.

stownsen914 · 10-31-2022, 08:32 AM

Are there any scratches or pitting on the sealing surfaces, that could give oil a path around the seal? The case looks OK from the pic above.

thetorch · 10-31-2022, 08:50 AM

Quote:

Originally Posted by stownsen914

Are there any scratches or pitting on the sealing surfaces, that could give oil a path around the seal? The case looks OK from the pic above.

no, and they didn't leak before i put new seals in. It started when I reused a seal that was one year old, that was a mistake. Then went to a red seal. That didn't work. Back to green.

Flat6pac · 10-31-2022, 10:16 AM

I don’t see it, there is no pressure there and the seal will fill the cavity
Although it’s under oil all the time, I’d have to look elsewhere
Bruce

gled49 · 10-31-2022, 02:59 PM

I’ve used red seals, green seals, used seals, all with DC 111 never had a leak in 40 yrs. I agree there’s another problem.

thetorch · 10-31-2022, 03:43 PM

Love the skepticism -- that's often warranted and helps us be methodical.

This time, though, it was just the seal. New seal has fixed the seeping.

thetorch · 06-15-2023, 06:46 AM

To update the thread, the drop returned.

I have tried multiple times to fix this with new seals. I have put a boroscope up between the case and the cooler to be sure the tech bulletin jb weld seal, acorn nuts/through bolts and upper seals were not the source. They are not.

It is verifiably not coming from the triangle of death.

It forms a drop at the bottom half of the lower oil cooler seal only. Maybe there is a scratch on the cooler or case that is allowing a tiny amount of oil by. Seems to happen when the motor cools, not when driving, though it's difficult to tell.

I see no other place the oil is coming from. The cooler (fins, etc.) are otherwise spotless -- but replacing the cooler feels like the only thing left to try, despite the cost. Not sure.

It's maddening. Some that folks say they have never had a problem here, and some folks say they always have a problem here. It's a tiny drip so I may live with it, though I feel like this should be soluble.

Latest pic of the cooler side lower.

Otherwise, the rebuilt 3.4 is an absolutely terrific power plant for this car. So much fun.

PeteKz · PeteKz's Garage

Live with it until you have another reason to pull the engine. In the meantime keep watching it to be sure that's where the leak is coming from. Over time, you might discover something else.

thetorch · 11-21-2023, 06:08 AM

Update for posterity.

This tiny drip continued, and in frustration I bought a new cooler. So far so good.

When pulling the engine for something else, and because I opened it on the stand, I confirmed again it's coming from the bottom half of the lower seal, nowhere else.

I checked the face of the cooler for flatness.

Very, very slight high spot on the mid-vertical face of the cooler seems to have caused the bottom of the cooler to be very slightly off the case which you can just make out in the picture. Must have been preventing full squish of the seal at the very bottom. It seems these can slightly warp over 35 years of heat cycles.

I have lapped the face flat, and now have an extra engine oil cooler. Expensive lesson learned.

thetorch · 11-28-2023, 07:19 AM

Never mind -- new cooler, same issue. This minor saga continues. Fairly stumped at this point. The case has machine marks inside the lower seal area -- perhaps they are preventing a good seal? You would think the rubber would easily seal there. Seems to happen after a drive during cool down cycle.

If it's not coming from the seal, it's extremely sneaky in getting to that point without leaving a trace.

Testing something else now.

callard · 11-28-2023, 01:15 PM

With the machine marks, perhaps it has been cut too deep. I just checked a '70 case and the depth is 5 mm from the lip to the base where the rubber gasket sits.

thetorch · 12-04-2023, 04:22 AM

Hoping this is the last post on this. The senior members saying "look elsewhere" were correct, and I was wrong. Despite having proactively repaired the casting weakness under the cooler prior to rebuild, with no evidence of a crack, I think a hairline crack developed.

Had to clean it out and repair again. Fingers crossed but at least the source of the leak is known.

Earlier repair looked good...

but it was cracked under the epoxy.