3.1L V6 Thermostat Housing Bolt size?
Joined: Apr 2010
Posts: 12,605
From: Mentor, Ohio
It has been a while, so I don't recall off the top of my head. But knowing GM, I am guessing 10mm or 13mm. You should be able to get a socket or wrench on them to check.
Typically when I change a t-stat on a 3100 or 3400, I remove the throttle body and I get pretty good access to the housing. Some take out the exhaust cross over pipe.
Typically when I change a t-stat on a 3100 or 3400, I remove the throttle body and I get pretty good access to the housing. Some take out the exhaust cross over pipe.