My car has been running hot since the engine install, so I took the thermostat out and tested it. In water, it didn't open until 210 degrees, which is about where the car has been running, and that seems a little hot. So I bouight another brand of t-stat, and it started to oped at about 190, but wasn't fully open until 200. It said it was a 180 t-stat on the box, so what does that mean if that isn't when it open? The guy at autozone told me these cars are made to run at atleast 220, and I said I think he is wrong. Are both of these thermostats bad, or is opening at 190 okay?

 

The stock t'stat in the LT1 is 180degF, and thats when it should open. Rob/Shoebox has a test instruction on his tech page.

The stock cooling fans do not come on until 226degF for the first one (or low speed... depends which year you have) and 235degF for the second one (or high speed). The t'stat will not affect how hot the engine runs, only the point at which the coolant starts to circulate - unless of course it is defective.

Link to Shoebox Tech

 

Just wanted to say to Injuneer that you have a bad *** car!

 

Not sure this helps you, but here's my experience...

The stock thermostat (180?) in my car kept it right around 200 degrees under normal conditions and just under 210 when using the A/C. My stock thermo just died a couple months ago and I wound up replacing it with a Hypertech 160 unit. Now it runs at 175 while cruising down the highway.

If my memory serves me correctly, the stock fans will kick on at 226 to help cool the car down to the 200 area. If you're in stop-n-go traffic (and with the stock PCM programming) this temperature cycle will repeat itself.

Our cars came from the factory setup to run at or above 180 for emissions and fuel economy purposes.

 

So that means that I still have a bad thermostat then right? It seems like if the t-stat didn't open, or block off the engine, until the engine was at 210, then that is the temp the engine would run right? Or do I have something backwards, because I thought when the thermostat opened, it blocked off the coolant in the engine, since these cars use a wierd thermostat and reverse flow cooling. Then when the temp in the WP and radiator get cool enough, the hot coolant flows from the block and the cooler coolant goes in, and gets blocked off until there is more cool water to come in. Am I right, or am I thinking backwards?

 

But would a thermostat that waits too long to open cause the engine to run warmer? So if I get a 160 thermostat, it will only let 160 or so degree coolant circulate through the block, then block in off, until more coolant is cooled down?

 

The t'stat BLOCKS coolant flow from the radiator to the heads/block until the rated temperature is reached. Then it opens and allows coolant from the radiator to flow through the block. Once it is "open" it stays open until the coolant drops below the rated temperature. This insures that your engine will always run with at least 180degF coolant.

Once the temp is above 180degF, it just stays open and does nothing.

 

Yes, a thermostat that waits too long to open will cause the engine to run warmer. Sometimes as they age, thermostats fall "out of range" and don't open/close when they should. Some just fail immediately and stick in the closed or open position. To your second question, the thermo will close if the coolant goes below 160 and it won't open until the coolant on the backside of the thermostat rises above 160.

Since you live in MI, I would stay with at least a 180 thermostat. Otherwise if you drive your car in the winter the heater won't get above luke-warm. YOU'LL FREEZE YOUR BUNS OFF!!

 

Okay, I am still a little cofused about this. So say I have a stock 180 degree tstat, and it opens at about 195-200. Will my engine average around 195-200?

 

If the t'stat opens at 195degF, there is absolutely no way the engine will ever operate below 195degF. But you can still see higher operating temperatures. On a hot day, at idle, sitting in traffic, it is VERY normal for a car with stock fan temp on/off programming to sit at the middle of the temp gauge, or slightly above. That is 220degF. It will continue to heat up when the car is standing still. The temp will reach 226degF and the first fan kicks on. If it continues to go up, at 235degF the second fan kicks on. The fans should be able to pull it down to 200degF, where the cycle starts all over again.

When you go to high speed driving, the air flow through the radiator will generall keep a stock seetup below 200degF.

As far as the thermostat, once it opens, whether its at 160degF, 180degF or 195degF, it can not take any action to lower the coolant temp if it is above the point where it opens. Temperatures will continue to rise until the radiator and fans can bring it back down.

 

Well then I just don't get why I have tried 3 tstats, and done open below 197 or so. I just picked up one from the dealer, and I am checking it now.

 

How are you determining the opening temperature? Don't go by the dash gauge in your car, it may not be accurate (mine is off by 10degrees!) Sometimes the sending unit for the dash gauge (which is screwed into the driverside head) becomes flaky and doesn't report temps correctly. Just an FYI...

 

I had it in a pot of water, and used an accurate thermometer for cooking candy or something. I just tried another one, and it opened before 190, so I am just gonna go with that one. It is an AC Delco from the dealership. Now hopefully I can get the cooling system bled correctly this time. Thanks for all the help guys