I have what appears to be a rear engine seal leak. Maybe a couple of tablespoons a day. My mechanic told me that he would just leave it until it got worse. He said that excessive crankcase pressure may cause even a new seal to leak and he thought I might end up spending $300 dollars for nothing...<br><br>Any comments?<br><br>What should I expect to pay for a new one?

 

I would crawl under the truck with a really bright light and look at the engine side covers under the intake side for leaks on the back of those seals before I figured it was a rear main seal.

The design of the crankcase vent is such that, unless you pinch it shut, you will not get excessive crankcase pressure.

For the cost of replacement, I recommend calling a real Cummins Service Center for a quote. But, would expect to spend somewhere around $650 if it is a main seal. If it is the side cover seals, tighten the side cover bolts and see if that does not stop it first.

Also, for grins, tighten your oil pan and be sure you just have not got the pan loose over time (it happens) and the oil is just drooling out the back of the pan.

 

I don't know what mileage you have on your truck, but there is a TSB that covers the rear seal and it is covered under warranty for the engine. Mine was replaced by the dealer.<br>george

 

The rear crankshaft seal was leaking on my 89 at about 120000 miles more than I liked. I had it replaced at a cost of about $325. The seal itself was $80. It is a double lipped teflon seal that must be installed dry with no oil on the crank shaft or the seal (on that truck anyway).

 

I thought that I had a real main seal leak a while back so I ordered one when I went to put my clutch in. Turns out it was the input shaft seal on the tranny. Now I have a brand new $80 dollar real main seal sitting in the house. Maybe I will need it someday. Thanks for the info on how to install it. I did not know that you had to install it dry. Thanks

 

That installation tip was right out of the 89 service manual. The guy that I had doing the work didn't believe it either so I copied the pages and took it to him. Never had another problem.