Hi all, new member here and my first post. Got my 951 this past spring at which time I did the timing/balance belts and water pump. I now finally have a chance to do some other things.

I wanted to check the entire turbo coolant system. For the turbo coolant pump, everything checked out electrically but when I went to check the operation of the expansion tank check valve, it didn't seem to be working. I then removed the expansion tank and didn't find any check valve. Where is it supposed to be? I figured it would be in the rear-most fitting on the expansion tank but it's totally open. I'm concerned that I may not be getting coolant circulation through the turbo when the engine is running. Any help would be greatly appreciated.

Thanks.

 

I have completely dissassemebled that area twice...but I don't know exactly what a check valve is...i know where every hose and stuff is....but...sorry i can't be of help there buddy..lol

 

What's the check valve suppose to do? How did you test it if you couldn't find it?

 

If you go to clarks-garage.com Garage Shop Manual under Coolant, there is a coolant flow diagram with a good explanation of what the check valve does.

Basically, there is a suction connection to the main water pump (where the little turbo thermostat is) that is supposed to draw coolant coolant through the turbo. This connection splits with one connection to the turbo and another to the expansion tank. The check valve ensures that the coolant draws through the turbo and not simply from the expansion tank.

I tried to check it by drawing coolant through the expansion tank connection expecting it to not flow but it did. I found no check valve when I removed the expansion tank.

 

I found it! It's just a little flapper inside the expansion tank. It wasn't down in the closed position but dropped down when I shook the tank. Thanks.