Installing Thermostat

[Ben Rush]

I bought a new thermostat in hopes of increasing my horrible gas mileage. 93 SC2 DOHC. Can some one post a how to on installing this?

[Tom92SCm]

Jack up the front of the car (the thermostat is located under the AC compressor). Remove coolant expansion tank cap. Open the drain plug, either on the radiator or on/near the thermostat and drain the coolant in a large bucket. Remove lower radiator hose from thermostat. Unbolt old thermostat from engine block. Replace with new thermostat. Use a new gasket when doing this. And then just piece everything back to together. If your coolant is old (more than 2 years) or got contaminated when draining, use new fluid. A 50/50 mix is good.

Also, just how bad is your mileage? What's your driving style like? A thermostat can cause bad gas mileage, but I think the problem lies elsewhere.

--Tom

[Ben Rush]

Im getting around 22-25 MPG in a 5 speed, and I dont drive hard at all due to a dieing clutch. I changed my PCV valve already with no change. My temp reading neevr goes above 1/4 so i figure this will help, and Im a broke college student who cant afford 70 bucks for an EGR valve. So im trying all the cheaper fixes before I go to something expensive.

[Dr. Bob]

First, search the board and you'll find scads of threads discussing the ECTS, also known as the coolant temperature sensor.

On yours, there are two of them - one (one wire) provides input to the temp gauge, the other (two wire) provides to the PCM (powertrain control module).

If the two wire sensor is bad, it can give the PCM incorrect temp data - it can falsely indicate a cold engine to the PCM, the PCM then directs a rich fuel mixture which kills fuel mileage.

Check the how to's section - this repair is very simple and cheap. Easier than replacing a thermostat.

As for the thermostat, some additional notes to what was listed above.

There is a draincock on the bottom of the radiator. Be careful opening it... it can break and no, you don't want to break it. If stuck, you can pull off the lower radiator hose to drain the system.

On the front of the engine, there is a large radiator hose going into a housing held on by two 10MM bolts. On the bottom of the housing, there is another 10MM drain plug. Remove the drain plug from below.

It's a good idea to do this on a cold engine... you are working very close to the exhaust manifold.

When removing the housing bolts, use a 6 point socket if you can get it in there. These can get extremely stubborn - an open-end wrench can easily destroy the bolt heads and then you are in deep doo-doo. Do these from above.

You may not have to remove the hose from the housing, but it is easier to work on with the hose off.

The thermostat resides inside the housing. To remove the old one, you have to push it in and twist the bar that latched into the housing. Reverse the procedure to install the new one.

Somebody posted that you can buy a new housing with the thermostat already installed, but I've never done it that way.

The new thermostat should come with a new o-ring for the housing seal. Make sure that is correctly installed in the groove. I bought one a few years ago at Saturn for $14.

Be careful to not overtighten - remember you're twisting those bolts into an aluminum block.

[eljefino]

Does this (http://www.saturnfans.com/forums/showthread.php3?s=&threadid=26261) help?

[FrozenPilot]

At least you don't have a linear EGR like I do. I've spent too much chasing fuel mileage already and have narrowed it down to the egr (basically with a diagnostic i should have done before). Its going to set me back around $120.... looks like I'm gonna start donating plasma!