Engine Running Too Cool ?

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Clovis, CA
2000 Buick LeSabre

When I got back to the car from the grocery store, I decided to take the car for a little test trip and watch the water temperature. A/C was off for the whole trip. At the start of the trip, water temperature was 167F and ambient temperature was 70F. Took the car on the freeway for 21.5 miles. As soon as I got on the freeway, the engine starts cooling off. Stayed between 155F and 156F for the whole trip. Exited the freeway and drove about two blocks to the house.

During the time the car was sitting in the driveway at idle waiting for me to open the garage door, the temperature spiked to 182F. The same exact trip the day before with the A/C on, the engine reached a maximum temperature of 176F. Thermostat is not supposed to open until 192F.

What you guys say ?
 
OEM thermostat replacement only Merk. My grandparent's Trailblazer had the thermostat replaced and it ran warmer, turns out the Stant opening was a lot smaller than the OEM one.
 
Originally Posted By: zeng
Originally Posted By: Chris142
Thermostat stuck open

+1

Ive replaced probably half a dozen thermos in just mine and a couple of friends cars for this same behavior.

Replace the stat.
 
Maybe T-stat but maybe not. The way those are geared, along with the 3800 torque (if/when in good shape) they're barely loafing along at a steady (speed limit) on the highway.

Owners of others cars will not understand that my same generation with a 3800, could run at 40MPH IDLING. Bad side, shifting was anything but performance oriented, and the gearing and high torque wears down brakes faster, like a train pulling when you brake to slow down.

Up to you, you can pull the t-stat and test it in a pot of boiling water if you like, but at that point I'd throw a new one in just because it makes sense to do so while it's so accessible.

However if it were me, I'd warm it up first then drive it like I stole it to get the temperature up, blow a little carbon off the valves, and see if you get that typical temperature plummet that happens when coolant gets around the t-stat rating then suddenly cools down the engine a few degrees because it opened.
 
No need to over-analyze, no need for a pot of boiling water. It runs too cool and its the thermostat's fault. With the correct thermostat that engine will run pretty steady 194-197F on the highway.
 
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I just had this issue on my Malibu where the temp gauge didn't move at all from cold. Replaced the thermostat and all is well. I was getting a P0128 code. Do you have access to a scan tool?
 
I changed t-stats on both my Hyundais this summer. Both OE and both were 'lazy'. they would run about 180-183F n the highway. But in the winter when coasting and slowing down the temp would dip below the 180F marks. Since changing them the run 185F-190F.
 
I've already had the new ACDelco thermostat sitting in the box for about 12 years. I even have a couple of extra seals that go around the "saturn" perimeter. What I don't have is the thermostat housing gasket. I got two on special order. Nobody stocks them anymore. Thanks for the replies guys.
smile.gif
 
Thermostats with a rubber seal that wraps around the edge of the flange don't need any other gasket.
 
You're correct mk378, but when I changed the thermostat back in 2005, it was seeping coolant where the thermostat housing mates to the engine block. Prior to that from the factory, it didn't need a gasket.
 
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