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This article is now being maintained on HowTune.com: Chaning a thermostat on a GM 4.3 Liter V6

Nothing quite as fun for a weekend upgrade as the thermostat. It's cheap, It's easy, It's fun!... right.
There's 2 reasons to change this out, to lower coolant temps or to replace a broken one. They are made by many companies, and come in several varieties. Form stock temps, 180, and 160 degree. A lot of people are using 160 with out a problem, but there is some speculation that it can cause problems with the normal operation of the EGR and IC pump. So I opted for the 180.

lets go..


Step One: Removal

1)- Remove Air Box and intake crossover tube. Place a paper towel in the orange elbow at the turbo to prevent from dropping stuff in.
2)- Partially Drain the radiator enough to get the coolant out of the upper radiator hose.
3)- Remove the Upper radiator hose. (2 clamps) one at the radiator, and one at the front of the motor.
4)- Using a deep socket, remove the bolt on the front,driver side corner of the thermostat housing
5)- Using a complex set up of an extension, wobble joint, and short socket, you can get the the bolt in the rear passenger side.
6)- Remove the thermostat housing and thermostat.

Step Two: Installation

1)- Prevent Overheating: There's 2 ways to do this, you can drill a small hole in the thermostat to prevent an air pocket from forming when you refill the coolant system, thus causing the thermostat not to open. The other way is to make sure the motor is fairly full of coolant. Mine, I could see coolant in the cavity directly under the thermostat, this should sufficiently heat the thermostat and cause it to open at the right time. I haven't drilled a hole into any of the 3 I've changed, and haven't had a problem with one of them overheating.
2)- Place thermostat back into it's place, and replace the thermostat housing.
3)- Bolt the housing down, and reattach the upper radiator hose, tightening the hose clamps sufficiently
4)- Refill the Coolant system.

Run the motor, keeping the overflow tank full. Make sure the engine warms up completely. If it starts to overheat, then the thermostat isn't opening, most likely due to trapped air. You should notice that your engine temp gauge rests a little lower when it's working properly. ;P

thermo bolt thermo housing