Questions on leak down test.


New Member
Authorized Seller
Sep 13, 2013
Lacey, WA
Took my car , 7mgte, into the mechanic today because I am having smoke on decel and at start up when the engine is warm only. Compression was good on all cylinders, 160-165. He did a leak down test and got results ranging from 10%-25% on one of the cylinders. The motor has a fresh rebuild less than 2 thousand miles ago. Turbo is a new Boss To4e 61.

I am not sure exactly what they did when they rebuilt the motor in regards to the head, it's been a while.... I thought they at least did new seals, but ???? The mechanic said on the leak down test that it was going to the crank.

Any thoughts on what I have going on?

He asked what rings were used, and I don't remember, it's been a while. The car has been sitting for a couple years. He mentioned some sort of zero clearance rings, and if used will sometimes blow too much through the pcv system if it is one with no valve, which the 7mgte does not have. I did have some oil in my lower inter cooler piping last time I checked,but not a lot....


Dang Dude! No Way Man.
Staff member
Super Moderator
Authorized Seller
Apr 17, 2007
The leak down test will tell you where it's leaking from. That's the whole point of it. So if it was leaking 10-25% into the crank case it's the rings. Either bad rings or not properly broken in.

Valve stem seals usually smoke on cold start up but can smoke non stop if there really bad.