rear seal leak

[dusty613]

Rear seal '82 with 90K miles. Replaced 4000 miles ago. Leaking again. Now thinking I need to drop the crank and see if it is worn. Noted other possible leaks in the forum, replacement was done by experienced Chevy hands, and was dry for 4000 miles. Thanks Dan

[TimK]

Dusty,

Check to make sure you crankcase ventilation is operating properly. Excessive blowby can in the crankcase can pressurize your crankcase slightly if it is not venting correctly. This can cause the oil to be pushed past the seal. When the engine is at idle or at very fast idle, do you see a lot of blow by coming out the oil filler tube when the oil cap is removed? Do you feel any pressure if you place your hand over the oil filler tube? You might feel some pulse but you should feel any pressure.

TimK

[smcghan]

I have virtually the identical problem on my '82. I checked the filler cap and I have what I consider a LOT!! of blow by. And I seem to be having a lot more smoke out the tail pipe. I seem to be adding 3-4 qts. between oil changes also. I went to change the air cleaner and there was oil all over. Short of a rebuild how about plugging the two nipples on each side of the air intake, and putting a road draft tube on to the oil filler nipple. Other than this the engine runs great. Steven

[TimK]

I don't see any point in bypassing the crankcase ventilation and letting it vent to the atmosphere. Here are the reasons why:
1. It doesn't solve your problem of excessive blow by. A set of new rings should fix that.
2. Your engine is desiged to burn oil and does so very well. All the oil vapor that is being pumped out of the crankcase and into the intake is being burnt as fuel. If you are going to put 1 gallon of oil in between changes you might as well burn it as opposed to spraying it on the underside of the truck and on the roadway.
3. Of all the pollution controls we have to deal with, the crankcase ventilation is rather benign. There are probably no benfits in bypassing this. This is not the same as the EGR (exhaust gas recirculation) system which bypasses exhuast gasses back into the intake.

TimK