[nike_sasquatch]

My Engine Is Running Way Too Cool! I HAVE A 1995 JEEP GRAND CHEROKEE LIMITED V8 4WD. It Runs On 100 Degrees For A Long Time And Then Gets Up To 130 And Only Goes Up To 160 If It Is Really Hot Outside And The Jeep Has Been Running For A Long Time. Does This Sound Like The Thermost? I Think The Engine Really Is Cool Because The Oil Pressure Takes A Very Long Time To Get Down To 25 Psi When Stopped At A Stoplight. It Won't Get Down To 25 Psi Until I Have Driven Around For A Very Long Time. I See The Top Radiator Hose Attaches To The Front Of The Engine With A Metal Clamp Like The Clamp You Find On A Dryer Hose, Except It Is Smaller. If I Remove This Clamp And The Hose Will I Find The Thermostat Underneath It And Do I Need A Sealer Or Gasket If I Install A New One? Also, I See They Sell 195 Degree Theromstats And 180 Degree. Which Should I Get?

Also, My Check Engine Light Has Been On For Weeks, But I Don't Think It Is Related.

[driabyor]

i would say the thermostat is stuck open.

[nike_sasquatch]

I think I am getting better gas mileage with the thermostat stuck open. Does it hurt the engine to run it this cool?

[John in MA]

I'd tend to think it could be a thermostat, but it should _eventually_ get to operating temp if you give it long enough. I wonder if the temperature sensor is out of whack too. Running cool isn't good for the engine. Oil doesn't thin out, emissions are funky.

And lose the caps on all the words that aren't names or starting sentences.

[nike_sasquatch]

Maybe I shouldn't have driven 5,000 miles with the engine running cold using 10w-30 synthetic oil.

The engine almost overheated 20,000 miles ago, so I had the coolant flushed and they put in a failsafe thermostat. Everything worked fine for about 15,000 miles and now the engine is running cold!

[Phil Gerard]

It's pretty much impossible for your engine to run at 100* - 130* in the summer even without a thermostat. The friction the engine produces will get it up to the 190* range.
So:
1. You need to check your check engine codes. They can be related. Information on this I believe is up in the FAQ Stickey.

2. I agree with John - likely you have a temp sensor wacky. I believe that the guage sensor is near the thermostat housing while the PCM temp sensor is on the engine. Luckily the guage sensor has nothing to do with engine operation.

Anyway turn the key on and off 3x and then leave it on and count the engine light flashes.

Phil

[nike_sasquatch]

I bought an engine temperature sensor today. Looking at the vehicle from the front, there are two sensors. There is one sensor right next to where the thermostat is on the right side. There is also a sensor on the left side of the thermostat a little farther away. Which sensor is the engine temperature sensor? Both sensors look the same!

[GreenDean]

you want the temp gauge SENDING UNIT, not the engine temp SENSOR.

The sensor just talks to the computer.
You want the sending unit for the gauge.

Make sure you have the right part first.

[nike_sasquatch]

They had to order a temperature sending unit, so I should get it by Tuesday. Should I go ahead and replace the temperature sensor or just return it? Also, should i replace the thermostat while I am waiting for the sending unit and see what happens?

[nike_sasquatch]

I drove the Jeep today in 60 degree weather. The temperature gauge never got very far above the 100 degree mark. I drove about 10 miles. Anyway, if the thermostat was really locked open, would the heater ever get warm? The heater did get warm. Also, would the oil ever thin if the temperature in the engine only got up to 160 or so. It takes forever for the oil to thin to the point of reading 22 psi when the vehicle is stopped. Should I change the thermostat now or wait for the temp sending unit? Also, where is the temperature sensor located? I may as well change that since I already have one. Thanks!

[Woody]

If you are getting heat, you are at normal operating temp, or at least close to it.

[nike_sasquatch]

Maybe I can cold start the engine, grab the upper radiator hose and wait several minutes to see if I feel a surge of heat through the hose and that will tell me the thermosat is opening?

[jack9580]

i would spend the $10 and put in the thermostat it should only take 20 min to swap and refill the cooling system and that has got to be cheaper than the temp sender

[Woody]

If you are getting heat though, it means the sender isn't working properly. You won't feel much at 130 through the lines.

[GreenDean]

lett he jeep idle for about 10 minutes. then try and grab the upper radiator hose.

if you burn the hell out of your hand. its at normal operating temp.

if you can grab it and hold onto it... its running cool.