What causes a Thermostat to stop working? Just curious because my car started over heating tonight. We did some test and found out the fan is not coming on. Thought it might have been a bad fan but ran power to it and it worked fine.

So we checked the hoses. Upper radiator hose is hot and the lower radiator hose is cool. Has to be the thermostat, which we are going to change tomorrow. Which is why I was wondering why a thermostat just suddenly stops working?

 

Check your fuses, there is a 20 for the fan that might have blown. Thermostats go bad over time, they get old.

 

We checked the fuse before we felt the hoses. From what I been hearing and I never knew before tonight that if the hose temps are that much different to the touch then chances are good that it is a thermostat.

 

It definetly sounds like the thermo is staying in the closed position, which is common. luckily, it's inexpensive part.

 

i experience this three weeks ago...thought it was the the thermostat and the fans worked when straight power was applied...but it ended up being low coolant

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by IntegraGSR-Turbo &raquo;</TD></TR><TR><TD CLASS="quote">i experience this three weeks ago...thought it was the the thermostat and the fans worked when straight power was applied...but it ended up being low coolant</TD></TR></TABLE>

Should be the first thing you check

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by IntegraGSR-Turbo &raquo;</TD></TR><TR><TD CLASS="quote">i experience this three weeks ago...thought it was the the thermostat and the fans worked when straight power was applied...but it ended up being low coolant</TD></TR></TABLE>

HMMM

If your car starts to overheat then the fan comes on right? So even if you had no coolant at all wouldnt your fan still come on? The coolant doesnt control the fan from what I know. Anyone else have any thoughts on this comment?

 

well if you have low coolant it wont hit the thermostat...cuz that is right where the sensor is...if there isnt enough coolant to heat it up it wont get hot enough to make that connection

 

Yes the fans will still come one. They turn on when the engine reaches a certain temp

 

one more thing i was overheating because of this replaced the thermostat didnt work and then added coolant worked perfect

 

the fans come on when the switch reaches that temp not the motor the switch could be bad or low coolant...the switch is a ground switch and when made hot it makes the connection

 

Even if the coolant is low its still going to circulate. 10 seconds problem is the coolant isnt circulating. Mostlikey because of the thermo being stuck in the closed position.

 

not saying your wrong mike just saying exactly what my car was doing...the switch is right there where the stat opens...i even replaced mine and it didnt do anything...immediatly after i added coolant they came on

 

If the system is low on coolant, the fluid doesn't come into contact with the switch, just hot air. The switch isn't designed to operate with hot air, but hot coolant. Once the system is properly bled and coolant reaches the switch, the fans come on, if the temp is up of course. I have seen this many times.

I have seen people replace many parts and become frustrated when they can't get their cooling system to work properly, when all along it was a slow leak that bled coolant out of the system until the level dropped low enough to overheat the engine. And once again, when the level is too low, the fans won't come on.

My car doesn't overheat even if the fans aren't on unless it sits at idle for more than 20 minutes, and this is in the heat of FL. When the car is moving, plenty of air flows thru the radiator keeping the temp down.

If you have an overheating problem, this is the order of possible causes that I check: check coolant level/ bleed air out of system, replace thermostat (cheap insurance), look for pinhole leaks (that might not be apparent) that bleeds coolant out of system, check fan operation, then test radiator, and lastly, check water pump for coolant weepage or possibly test for flow thru system. You can also have the system pressure tested.

A warped head or blown headgasket can cause overheating also, and should give off a sweet smell at the exhaust.

Sorry about rambling, just bored this morning, good luck to you.

 

i got a 93 ls that over heats sometimes... but when it overheats i turn my heater on full blast and then it gonna go to normal temp.. what do yah think that causin this problem... and do yah think its the termostat stickin.. thanks.. in advance...

 

Well I just added some water and the fans came on. Car did not overheat. Which leads me to my next problem. Where am I losing coolant from?

 

My pin-hole leak was one of the 8mm hoses under the intake manifold, but also check the radiaor and heater hoses, and the radiator can leak also. Pressure testing can help by adding pressure (within reason) till the leak shows itself.