Could running hot ruin a thermostat?

[muleears]

Immediatly after an italian tune up in my 124 I was stopped by a cop (for an unrelated reason), anyway, after driving it hard and immediatly stopping, the hot soak made the car overheat. When I restarted it 10 min later it stayed very warm for a few miles. Originally the car normally ran 85-90* now it consistantly runs around 100* and up to 110* in traffic with the AC. All of this started after the overheating event. I have a #17 head on the car. What have I done? I am not losing coolant, don't see any coolant in the oil or oil in the coolant and not losing oil. The aux. fans seem to be working. Could I have ruined the thermostat? What else should I check?

[t walgamuth]

it seems unlikely.

i would verify operation of the temp guage as a start point.

tom w

[wbrian63]

Back in the day when I was a service writer, we routinely suggested replacing the thermostat on any car (any make/model) that came in with an overheating problem, even if the thermostat wasn't the cause.

I'll hazard a guess and say the few times we deferred to the customer's request to save $ and not replace the thermostat, fully 50% came back shortly thereafter with a sticking thermostat.

Just my 2cents.

[F18]

Pull the thermostat and put it in a pot of water and bring it to a boil...you can visually see if the valve is opening all the way as the water temp rises.
If you have a thermometer you can also check to see if it opens at the appropriate temp. Most thermostats have their temp. rating stamped into the side of the metal thermostat frame either in Celsius or Farenhight. The Thermo element/spring fatiques over time and does not expand and contract at the same rate leaving the valve shut for too long and then only patially opens.....but then its to late....the engine is running hot!
If it shows any problems opening or only partially opens just replace it. You cannot fix them.......Your thermostat is probably 20 years old and already on its last legs 10 years ago.
Good Luck!

[C Sean Watts]

There is a small waxy/plastic capsule in the center (of the sliding mechanism.)
If it is overheated even once it gets distorted and the opening/closing temps and rates are off, even if it has a good spring. Thermostats were designed as a replaceable wear out part.

[muleears]

I know this is related to the overheating incident, I think I'll try a new thermostat and see what happens. If I'm lucky it will be a cheap fix.

[babymog]

I don't test thermostats.

As cheap as they are, by the time I've got it apart I'm going to have the new one ready anyway, might as well install it.

[Chas H]

Originally Posted by babymog

I don't test thermostats.

As cheap as they are, by the time I've got it apart I'm going to have the new one ready anyway, might as well install it.

I've bought new t-stats that are bad. Testing costs little.

[lietuviai]

It's an easy job to replace one on a 603. I have a spare new O-ring if you're interested.