Volvo 940 Seals and using additives

Hi, I recently purchased a 1995 volvo 940 turbo with only 137000 miles on it that I really love. However, She’s leaking oil a lot out of the rear-main crankshaft seal, which is an expensive fix. I picked up some AT-205 RE-SEAL which I wanted to try out, then I got worried that it might mess something up, being how Volvo tends to be very specific as to what one can and cannot use as far as fluids. I believe there is synthetic oil in the engine now. Does anyone know if it is safe to try out the re-seal or should I just bite the bullet and get the thing fixed ? Thanks !

I’m not familiar with particular product but I don’t see that it will harm anything considering the situation.

A rear main can leak for any one of several reasons. One could be that the rubber has aged and hardened, which is causing the seal to not conform to the surface of the crank journal. This product MAY help that but only up to a point. If it’s very bad then it will do little.

The other is that the crankshaft and bearings could be worn out which is then allowing the crank to move either up and down or back and forth in the bearings. This can beat the seal to death.
The car may only have 137k miles but it’s also an aged Turbo and if the previous owner was in the boost for 120k miles of that total anything is possible.

You could try taking a pry bar and carefully seeing if the crankshaft has excessive movement back and forth. Up and down is a bit harder to gauge.
This could be especially true if the car has a manual tranmission. (heavy use of the clutch, etc.)

Thanks. I’ve heard that the seals on these engines are typically problematic. I’ll check out the crankshaft motion as you suggested and try out the re-seal stuff. It seems like the engine had too much oil in it when I first got the thing too, and the leak is not as bad now. Just concerned. It is an automatic trans. If it is the crank-shaft, what do I need to do, replace the bearings ? Yikes !

Also do you think using 10w-40 would help ? of is it too high a viscosity for this engine ?