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Old 09-30-2003, 04:46 PM
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thermostat

I did a search of past postings and just couldn't find anything that answered my question.

I replaced an old thermostat due to it was starting to stick shut and try to overheat my stock 350. I felt the upper radiator hose when the guage showed it was heating up and the hose was cold. It only happen occasionally, but I replaced with a new 195* thermostat.

With the new 195* thermostat in place it does the exact same thing still. I let it heat up to about 220* and felt the upper radiator hose, and it was cold. Revved the motor to about 2000 rpm a couple times and the thermostat opened and temperature dropped to 195* range.

There seems to only be a problem when the motor is started when cold and the thermostat doesn't want to open after reaching specified temperature. Once it opens, it doesn't seem to have any further problems until the motor is restarted cold. The hoses, cap, and coolant are new and water pump appears to be fine.

Do you think I just got a bad thermostat? Is this common, I never had any problems with new thermostats before.
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Old 09-30-2003, 05:20 PM
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Are you sure there isn't air in the system? Air pockets can do strange things.


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Old 09-30-2003, 05:57 PM
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How about checking your fan belts. They can be loose enough and not squeek, or something with water pump needing more RPM to work.

On the thermostat:
I drill four 1/8" holes on the outside rim.
Make sure one of them is at the 12:00 position.
This stops all air cavitation and lets all the air out.
Try to keep the upper hose as low as you can for a smaller air pocket.
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Old 09-30-2003, 06:42 PM
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I read your past postings about the four 1/8" holes and plan on doing that.

I appreciate the responses, I'm going into town tomorrow to get a new thermostat. I guess with the millions of thermostats produced, there has to be a few bad ones that slip through and into the stores.
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Old 09-30-2003, 10:13 PM
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Its also possible that your water pump impeller has deteriorated to a point that it won't pump any water at low idle rpms.
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Old 10-01-2003, 05:48 PM
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Good point Jmark, I forgot about that one,
also what about the inside of the radiator, are you getting any flow thru it ?
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Old 10-01-2003, 06:07 PM
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My wife drove the vehicle to work and back today, which is approx. 50 mile round trip and not a single problem today. Maybe it was air in the system, but I just don't think that was it. When I changed the thermostat the first time, I only drained enough coolant to drop the level about 1/4" below the flange where the thermostat sits. When I was topping of the radiator, I had the engine running with the radiator cap off and I could see coolant flowing pretty good from the heater return hose. The radiator looks really clean as far as I can see.
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Old 10-01-2003, 06:27 PM
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So if I read that correctly she's running good again.
Glad to here. Updates are always nice.



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