new oil leak

[Pilladose]

Hello everybody, I have a question, I know i've read about the this some time ago but couldn't find it. We just installed a banks turbo on my brothers '84 blazer w/6.2. There was no leak before the turbo install. Now this thing has a massive leak looks like it running down from the rear main. This does not have the EGR. Is this caused by the case becoming pressurized? Any suggestions? How to repair?
Thanks
Edgar

[BobND]

I've never installed a Banks turbo, however, the way a 6.5 turbo is set up, the crankcase vent (the outlet of the CDR) is plumbed into the INLET side of the turbo, so the crankcase vapors are sucked into the compressor side of the turbo, and blown into the intake manifold.

How is the Banks set up? Originally, the crankcase on a 6.2 was vented into the intake manifold, so if the vent line(s) from the CDR are still connected to the intake, you'd be pressurizing the crankcase with pressurized air from the turbo.

How is this supposed to be set up on a Banks... I'm sure the vent tube(s) would have to be unhooked from the intake, but where are they supposed to go... into the turbo intake, or "overboard" like Cummins???

[john8662]

It's somewhat common to start having rear main seal leaks after the turbo install, as it does affect the way the CDR system works. But here are some things to check on first:

Several things can leak, one thing comes to mind being the vacuum pump. When it fails, you can have oil coming out of the pod itself, and it will run down the back of the engine and look like a rear main seal leak. The gasket that mounts the pump to the engine block can also leak, but this is somewhat rare.

You could also possibly have a fuel leak on the fuel return system (lines from injector to injector) that can cause diesel fuel to clean off the oil on the engine making it look like an oil leak by the time it gets to the ground.

If the above mentioned areas don't reveal your leak, you could have a rear main seal leak. To tell you will want to pull the tranny inspection cover to see if that's what is leaking (rear main). If it's the rear main seal leaking you should be able to look up on the inside of the flexplate (engine side) and see part of the crankshaft. If it's all oily from fresh oil, you can bet you found your leak on the main seal. If the crank is dry but the rest of everything else nearby is oily, then it's probably the pan gasket on the rear. Either way you're going to be pulling the pan.

The 84 model 6.2's had a rope seal, that is somewhat sensitve to leaking when pressure changes in the crankcase, but once leaking it needs to be replaced. The new replacement seal is a viton seal. A cause for a rear main seal leak can be a faulty CDR valve, the tuna can looking valve that sits above the alternator. There is a way to test it, but you are best of replacing it for good measure in my opinion, I'll try and dig up method of testing it for you though..

[BobND]

John,

How does the crankcase vent get re-routed with a Banks turbo install?

[john8662]

Bob,

The blow-by from the CDR valve gets sucked in before the turbo right at the air box in the Banks setup. Banks does away with the CDR metal tubing that goes to the intake manifold because they take one 1" ID tube to the airfilter box to be injected on the clean side of the filter and before the turbo compressor.

[jcomp]

The CDR vent on the Banks system is routed to the air cleaner box.

My engine did not leak until I put on the Banks system, then it was severe. Turns out about 1/3 of the rear main seal was missing.

[Pilladose]

Thank you for the replies. Looks like we're going to replace the CDR and and the rear seal and go from there. I cleaned the vacuum pump, their is nothing coming from it and i have no fuel from the return lines leaking. So tomorrow we'll try and finish her up. Thanks again.
Edgar