Since these turbos came to me used, I won't mention what brand they are; but it's a good extra place to 'check' prior to bolting on new turbos; especially with the thread a few days ago.

The backing plate to compressor housing was leaking. So I disassembled both of them trying to find a solution.

This is what I found. Notice the 0ring grove, but no o-ring:



O-ring in place:



This resolved my leak between the compressor housing and backing plate. NO RTV, gasket or sealant needed. Though, I'd have used pipe thread sealant compound if there had been no other solution.

Moral of the story: do your boost leak check any time you work on the car. I found things leaking that I wouldn't have thought to ever leak.

 

I say this every time I talk to a client... they do not understand and I think give too much faith in the components and or in the installer... 50% of the success is the install/pressure testing....