Faulty thermostat?

[Falcon_LS]

This is on my 2001 Grand Marquis. Recently, I've noticed it takes a bit longer than usual for my engine to reach operating temperature, but it eventually does. I figured the thermostat is probably the culprit, but haven't had the chance to replace it yet. I installed my 180 F thermostat (Motorcraft RT-1144) back in May, it boggles my mind as to how it could fail so early.

Anyhow, using my scan tool this evening and streaming live data, I noticed my engine coolant temperature was 204-206 F! So there's something rather unusual here, and I'm beginning to think it could be more than just the thermostat. Just wondering if anyone has any input as to how this could be. Thanks!

 

[oilboy123]

Temp sensor going bad or coated with something........

Are you saying that it always reads 204-206? Or just reads that hot for a bit? Why the low temp thermostat? Stock should be 195 degree. How hot is it in Kuwait?

 

[Falcon_LS]

When the engine's cold and I take it out on the highway, it warms up to 180 F. If I stop at a light with the transmission in drive and the brake applied, it goes up to 204-206 and stays there all the time. When the engine is switched off, cooled down and restarted, the same cycle commences.

The temperature right now is 65-95, depending on the time of day.

I went with a lower temperature thermostat to keep it running a bit rich, and am planning a tune to get the electrical fan to turn on earlier too. Also looking to get colder plugs and a tune for 98 RON fuel for more timing.

 

[sr17]

I too wonder if I got a faulty thermostat installed when my van got a tune up back in June of this year.

Before the thermostat was replaced it usually ran at ~195F if my memory is correct.

Since I got the new thermostat installed it barely reaches ~150F on the temp gauge, even after extended stretches of highway driving.

The only time it will climb towards the 200F mark is when I tow the boat up long steep hills during the summer.

What temp should me van be running at? Does it hurt the engine when it runs as cool as it does?

 

[Rooy]

Originally Posted By: sr17
I too wonder if I got a faulty thermostat installed when my van got a tune up back in June of this year.

Before the thermostat was replaced it usually ran at ~195F if my memory is correct.

Since I got the new thermostat installed it barely reaches ~150F on the temp gauge, even after extended stretches of highway driving.

The only time it will climb towards the 200F mark is when I tow the boat up long steep hills during the summer.

What temp should me van be running at? Does it hurt the engine when it runs as cool as it does?


Sure sounds like a bad thermostat. Get a new one. OEM are usually best, but more expensive. It should run at whatever temp thermostat your car calls for (usually around 195F). Running too cold isn't ideal. Oil isn't getting as warm as it should to burn off condensation. Fuel economy will be lower.

 

[Chris142]

The stat only controls the lowest temp. Once it's open the rest of the cooling system controls the upper temperature. 206 is normal for your car when it's sitting still.

The radiator fan probly comes on @ 206 and thats why it stays there when idling. When your driving fast the air flowing through the radiator keeps it near 180.

It's working as it should.

 

[beast3300]

Does your 01 have a mechanical fan or electric fan(s)?

Either way it is programed to operate at a certain temperature. If it's electronic fans then the PCM had the on and off desired temps. They are going to be tailored around the stock stat. If it is mechanical, then most likely it has a thermo-clutch that will spin the fan faster with more temp.

 

[Quest]

Thermostat can become "lazy" too, as opposed to drastically fails (aka "wide open" or "wide shut").

When in doubt, always consider a new factory OE thermostat and see if that solves your problem.

Afterall: thermostat comes with defined service life and as the car ages/with sufficient number of thermalcycling, it will give up.

Q.

 

[Errtt]

I'd change the stat. It's cheap and a good start. I have also seen bad radiator caps cause folks headaches because they never suspect it.
Back in the days, some folks took out the stat and wondered why they overheat (some vehicles) - because the water pump was good and efficient (good impeller & design) and the coolant didn't stay in the radiator long enough to cool down.

 

[ComfyShorts]

Like somebody said earlier the thermostat BEGINS to open at the temperature stamped on it. If its sitting at 204F while its idling with electric fans cycled off thats absolutely normal for most cars.

 

[SteveSRT8]

aftermarket stat is always a suspect.

Remove it and boil in a pan of water with a thermometer and observe it for proper opening/closing.

No matter which stat you choose you may not be able to influence the traffic temp much due to programming of electric fans, etc. Running cooler without some tuning adjustment is not always beneficial.

 

[Rick in PA]

A 180F thermostat sounds low. It's been a while since I was involved in general auto repair, but as I remember it, 195F was the standard, 180F was a lower temperature or "colder" running thermostat.