Getting into the trans conversion (BW35-to-M41) and I'm staring at the rear main seal. So do I just replace the seal with the same type or is it really important to upgrade it to a later style as I've read about? I have to do one or the other as it appears to be leaking a wee bit.

Hello,

The old style felt seal works okay when the engine is fresh and has low blow by past the piston rings. But as the motor gets older and the blow by increases, the felt seal lacks in comparison to the lip seal in its ability to withstand higher pressures.

The only possible downside to updating to the lip seal housing is unintentionally creating another oil leak from the oil pan gasket.

It is not uncommon for the section of oil pan gasket under the old rear seal housing to tear when removing it to replace the housing.

Even though I have used a section of new oil pan gasket and plenty of oil resistant silicone, I occasionally still have leaks which I usually have to attribute to a deteriorating old oil pan gasket.

So if the oil pan gasket is very old, you might consider changing the oil pan gasket at the same time as updating to the lip style rear crankshaft seal housing. FYI, the same applies to updating the front timing cover or changing timing gears/camshafts.

And I find it easier to pull the engine out of the car to replace the oil pan gasket as opposed to doing the job with the engine in the car.

You can't remove the oil pan without lifting the engine or lowering the front suspension crossmember and I don't recommend either with the transmission removed.

With the engine on a stand, its much easier to replace the oil pan gasket. And while the oil pan is off, you can check out the crank and rod bearings as well as the oil pump and oil pump seals.



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Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

If removing the engine is not practical or possible for you--at the very least loosen 3 or 4 of the pan bolts on either side of the seal housing. A seal housing from a B21-B230 will work for you but remember to use the two pan bolts that match the metric threads on the OHC motor's housing. -- Dave

Eric/Dave, thanks for the responses.

I really don't want to pull the engine at this stage of the game. It has about 100,000 miles on it so the bearings should be OK. I don't know the condition of the oil pump other than it is pumping oil to the top end quite well. So I'm going to attempt a fix with the engine in place. I, too, was thinking about just loosening the first few pan bolt a couple turns to facilitate the housing R/R and then hoping I can get everything snugged back up good and tight.

Do you guys know if someone sells the later seal housings, or am I off to a junk yard for that (which is perfectly OK with me)?

Oh, one more question. What are the differences in outward appearance between the original B20 seal housing and the B21/23/230 housing. I want to make sure someone hasn't already converted it.
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Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)

The original rear seal housings don't have alignment pin holes.

FYI, there is nothing wrong with an updated original seal housing if it is properly machined, which is what I usually sell as a kit with a new seal and gasket for $50.00. But I am out of them right now.

If you want, I have a good used one with metric threads or I can get new ones that are complete kits with a new seal and new gasket for $75.00.

--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502

Here's what I've got in there now. (Attempting to attach photo....)

If unable to see, as some browser may balk at not using a complete URL:


URL:
https://www.brickboard.com/IMAGELIB/_images/12471.jpg

Art's instructions on embedding links into messqages.



Happy St. Patrick's 2016!!










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Something, something, something, something ....

OK, I figured out the problem. I was missing the first "<" in the code. What's weird is that it shows the image "sometimes" when I call up that page. So, let's try this again.....

Lucky you---the modification has been made already---you're looking at the lip type seal. It is the same seal -- B30, B21, 23, 230. No worries now about broken oil pan gaskets. Don't remove the housing (unless you determine its gasket is leaking). Pry the old seal out -- fill the void on the new one with wheel bearing grease--that will keep the spring from popping out. Press or tap it in after making sure the lip (lubed with grease) hasn't folded back when you slip it over the crankshaft. -- Dave

That's cool. When Eric said the old version DOESN'T have locating dowel holes, I was encouraged to see them on mine. You know, that car has been sitting in my garage since I bought it 20 years ago. So I guess that seal mod has been practiced for a long time.

I'd like to drill two or three tiny holes in the seal, screw in some small screws, and use them to pull it out. Would you happen to know how deep the drill and screw can penetrate without bottoming out on anything inside.

Thanks for following me on this one.

"I'd like to drill two or three tiny holes in the seal, screw in some small screws, and use them to pull it out. Would you happen to know how deep the drill and screw can penetrate without bottoming out on anything inside"
It isn't that complicated. Slip a flat blade screwdriver under the lip of the seal and use the edge of the crankshaft as a fulcrum and just lever the old seal out. You only need to get under the lip just a bit. 1-2-3 - nuthin' to it. -- Dave

Gotcha. I'm always afraid of gouging something.

Any favorite brand of seal?

I noticed that with all my jacking up and down with the engine to get the BW35 out, that I've created a leak from one of the heater hoses. Well, they're only 43 years old. If they were going to spring a leak, now was the right time. (Additional access with the bell housing out of the way) One step forward - two steps back.

Thanks again.

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Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)

No, I don't have any particular "favorite" as far as the seal goes--maybe others have more to say. I'd count the the leaking heater hose as a blessing---better now than on the road at night in the middle of nowhere. Use Volvo originals if available. -- Dave

I have some seal housings -- $10 plus postage ($8). The original will have a flat metal ring retaining the felt seal and a wire clip fit into a groove to retain both. Reach me at ---fastforwardphoto(AT)yahoo(DOT)com----Dave