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Contemplating a rear main seal

soclosenotnear

Active member
Joined
Oct 12, 2011
Location
summerville, south carolina
1990 740 turbo aw71

My brother and I are trying to solve his rather large oil leak. We have meticulously cleaned the engine bay to try and track this down. We also changed the oil separator box for Volvo oe. Verified all pcv hoses are clear and even the small brass nipple.

After these efforts, he is still having to add a half quart every other day or so. He noticed a slight wetness around the box and also under the distributor. But then dry all around it, so couldn't be the major source.

Every time the car is parked, a small pool forms under where the engine and transmission meets. Has to be the rear main seal, yes? Oil pan gasket isn't great, but dry on the sump. I imagine this leak is likely worse under boost when he's driving and that's when the oil loss really happens. But it leaks even with the car off(?).

I've never pulled an auto trans in my life, but how much harder than an m46/m47 could it be. But that is a last resort so we are just trying to verify.
 
I don't have experience pulling an auto trans, but I am guessing that it is indeed your RMS. It could also be your front crank seal weeping and the oil will run along the pass side of the oil pan / block seam and drip at the block / trans junction.

I had a similar situation and a new RMS took care of a majority of the leak, but there is still a small drip that originates at the front crank seal. Worth checking that out as well.
 
You can pull the 6 bolts for the inspection plate. Use a small mirror and look at the seal. It probably leaking. Use a genuine Volvo seal and set it a little deeper than the old one. Have fun. I’ve done more than enough for a lifetime. Your going that far you may want to do bell housing orings and front pump seal. Check the bolts for the rear seal plate
 
You can pull the 6 bolts for the inspection plate. Use a small mirror and look at the seal. It probably leaking. Use a genuine Volvo seal and set it a little deeper than the old one. Have fun. I?ve done more than enough for a lifetime. Your going that far you may want to do bell housing orings and front pump seal. Check the bolts for the rear seal plate

Never done the bell housing stuff, usually not needed and if they're not leaking, I wouldn't mess with them. The rest of it though, dead on.

Pull the inspection cover (2 bolts into the BH, 4 into the block), take a look at the seal. ONLY use an OEM seal. I've tried a few different brands, none of them really lasted where the OE is still dry after a few years.
 
1990 740 turbo aw71

My brother and I are trying to solve his rather large oil leak. We have meticulously cleaned the engine bay to try and track this down. We also changed the oil separator box for Volvo oe. Verified all pcv hoses are clear and even the small brass nipple.

After these efforts, he is still having to add a half quart every other day or so. He noticed a slight wetness around the box and also under the distributor. But then dry all around it, so couldn't be the major source.

Every time the car is parked, a small pool forms under where the engine and transmission meets. Has to be the rear main seal, yes? Oil pan gasket isn't great, but dry on the sump. I imagine this leak is likely worse under boost when he's driving and that's when the oil loss really happens. But it leaks even with the car off(?).

I've never pulled an auto trans in my life, but how much harder than an m46/m47 could it be. But that is a last resort so we are just trying to verify.

All good advice about the use of OE rear seals only (I learned too late after foolishly buying the red colored aftermarket....always a slow drip). I must ask, is he running Dino oil or synthetic? I've seen several Saabs in the family that converted to synthetic, began to leak profusely. Both were converted back to Dino oil, and the leakage diminished significantly.
 
That's the car. I wasn't trying to beat a dead horse with the tranny question, I just wanted to clarify since there seemed to be some variance of thought on that but yes, I've decided to leave it alone and search elsewhere. Better safe than sorry. Thanks again for your time and input, everyone.
 
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Hey everyone and thank you for all the good advice. I am the brother with the large oil leak, I've been filling it with 10w-30 castrol gtx, but after some reading I was thinking about 10w-40 with seal conditioner or what not. Being hopeful that the thicker oil and addiditives would seal it up.

I'm putting it on a lift in the next hour and I should be able to give a definitive answer after that. If it does end up looking for sure to be the RMS I will pull the inspection plate

But one question that I just can't seem to word right on Google...on the intake manifold there is three small brass nipples where the snall pcv hose go, the wastegate actuator hose, and the boost gauge? If I'm thinking right...now me and my bro pulled the nipples off the ensure they weren't blocked. And all of then we're clear, but the one nipple that the pcv line goes to has only a small pinhole where the threads are, it's not oil crap, it's made with a tiny hole while the others are wide open. The vacuum diagram says I have the hoses on the right nipples, but my question is what the heck is the smaller one for? And where exactly does it go
 
Okay, so I just got it off the lift and found exciting maybe but unexpected things... So the sump is wet coming from under the box on the left side of the engine is wet the right side is soaked all over the starter and onto the sump and it looks like it's coming from the rear main? There is a forever drop of oil staying right underneath the distributor rear cam seal I'm guessing, another question I have is if it is the rear cam seal, can I lose that much oil out of there? Or does it sound like I have a crankcase ventilation problem? Being that the rear cam seal is at the back of the valve cover where the valves are I can't imagine I'd lose that much oil so quickly, unless it is combined with a whole bunch of other leaks due to PCV problems but we have cleaned all the PCV equipment to no avail, I am lost as of right now I don't know where to turn
 
For those that have the 2.4 system and are considering doing a rms . Make sure you mark the flex plate or you might get to have a rerun. I like to take the first bolt out and then give it a little shot of spray paint. Makes it fool proof to reinstall correctly.
 
For those that have the 2.4 system and are considering doing a rms . Make sure you mark the flex plate or you might get to have a rerun. I like to take the first bolt out and then give it a little shot of spray paint. Makes it fool proof to reinstall correctly.
This.

There is no rear cam seal. You have an o-ring on the distributor.
 
Okay, I'm sorry that was what I was referring to... Is it possible to lose that much oil out of the O-ring behind the distributor?

And the PCV problem is very confusing to me we replaced oil separator box with OEM and confirmed that all hoses are clean and clean them out anyways all the brass nipples are clear all hoses are clear is there another part of the PCV system that I'm missing?
 
I helped quell a RMS oil leak in a redblock by using 20W/50 dino oil: the leak went away.

With cold weather coming, time to switch back to 10W/40 to allow proper lube at initial start up, at least that's what I've been lead to believe.
 
Try the glove over the oil filler and see if inflates.

And flywheel always goes with gap towards starter at TDC on 2.4.
 
I will definitely try the glove over the oil filler when I get home in about an hour, I have tried the oil filler loosening and all it does is vibrate on top of the oil filler hole which I've heard means there's pressure and it's supposed to be sucked down and not move at all but to me that kind of seems far-fetched I'll do the glove / Saran Wrap test and let you guys know
 
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