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Symptom of dying thermostat?

 
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Old 13 May 2008, 08:12 pm
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Default Symptom of dying thermostat?

Hi All -

Have a question about the symptoms, if any, of a dying thermostat.

The car in question is a 2004 PT Touring Edition, approx. 52000 miles.

Within the last month we have had to replace the water pump (which blew on the way to the dealer to get it worked on!) and the timing belt. Other than that, there have been no major issues with the Cruiser.

Today, however, there has been an issue.

At lunch time, when my wife went to start the Cruiser after being parked for several hours, the needle on the temperature gauge went to the top and "binged" at her, then it dropped back down to a hair above midline. This afternoon when she went back to work, she said that the needle would oscillate between redline and the hair above midline, taking about a block driving distance to cycle back and forth.

I told her that this sounds suspiciously like the thermostat is dying / dead. Years ago I had a little Subaru XT Coupe that would do the same thing. I would start the car and the temp. gauge needle would peg then drop down to about midline and then cycle back and forth. Replaced 4 thermostats in the span of a year, never did find out what was the cause - changed out the radiator, did a full flush, wired the aux. cooling fan to run all the time - it cycled until the day I traded it in. Never overheated, though.

So, am I correct in assuming that the symptoms are a dying to dead thermostat? The dealership that we go to work on the car is about 80 miles away, most of that interstate driving. We were planning to take the car in on Friday, but should we think about getting it towed up? (Have AAA Plus coverage w/ 100 miles of free towing.)

Thanks!

Tony Perreault
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Old 13 May 2008, 08:33 pm
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Default Re: Symptom of dying thermostat?

Thermostats don't work that fast in making the car overheat and then cool off. I'd say your problem is the coolant sensor sending unit located just below the thermostat itself.
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Old 13 May 2008, 09:12 pm
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Default Re: Symptom of dying thermostat?

Why do you have to replace your thermostats soo often? Where do you live!?!?
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Old 13 May 2008, 09:17 pm
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Default Re: Symptom of dying thermostat?

Quote:
Originally Posted by CREWZIN View Post
Thermostats don't work that fast in making the car overheat and then cool off. I'd say your problem is the coolant sensor sending unit located just below the thermostat itself.
Thanks! Just to clarify, the car isn't actually overheating - it just thinks that it is!
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Old 13 May 2008, 09:20 pm
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Default Re: Symptom of dying thermostat?

Quote:
Originally Posted by ucantcme View Post
Why do you have to replace your thermostats soo often? Where do you live!?!?
New Mexico. The dealership where we get the cruiser worked on is about 80 miles away. There is a local dealership, but the quality of the mechanical work is, well, sad. They are always running ads in the local paper for mechanics...

And it was my Subaru that was eating thermostats - not the cruiser. I ended up just living with it. As I mentioned, the Subaru never overheated, even when the thermostat was acting like a spastic jack-in-the-box...
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Old 13 May 2008, 09:37 pm
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Default Re: Symptom of dying thermostat?

Quote:
Originally Posted by CREWZIN View Post
Thermostats don't work that fast in making the car overheat and then cool off. I'd say your problem is the coolant sensor sending unit located just below the thermostat itself.
Agree. Sensor, not thermostat. That's the only thing that could cause a visable fluxuation in the temp reading on a normal car. Though with how hard wired the engine computer is on the PT Cruiser, it could also be a computer issue. But the water temp sensor is the cheaper culprit to check on first. Not sure how the PT Cruiser is. Some cars have a seperate water temp sensor for the computer and another for your dash reading. Some use the data off a shared sensor. If it's a shared sensor, then it would also affect your power as it would cut the ignition timing to compensate for what it'd see as a hot engine.

Any thermostat would result in the temp pegging cold or possibly hot, radiator or water pump issues would result in the temp pegging hot. But neither would go hot on a car that hasn't been driven in several hours.


Also, a good thermostat is usually designed to get stuck in the open position rather than the closed position when it dies.

I think you wasted quite a bit of time with unneccesary repairs on your Subie. Sounds like a typical mechanic repair job, though. Throw money at the problem until something works. God forbid a mechanic actually use some brain power to diagnose an issue.

So no, I wouldn't bother towing it. If it starts going to hot, and staying at hot .... then you can worry. But I wouldn't even bother having a garage do a temp sensor. It's usually right at the top of the water neck, and usually just need a pair of vice grips to take the old one out. A little plumbers take on the new one's threads, and screw it back in. No fluid draining required.
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Old 14 May 2008, 07:13 am
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Default Re: Symptom of dying thermostat?

i agree with crewzin !!
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