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Model 90 Thermostat


31Buickroadster

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Currently, there is a bolt wedging open the thermostat arm going to the shutter. What should be done to diagnose the functionality of this mechanism?

 

Usually the bellows on these fail.  Whatever else you may do, refrain from placing this unit into a pan of boiling water to test.  If there is any chance to get yours working that will usually ruin it permanently.  I would suggest talking with these folks who may be able to help you out:

 

http://www.classicandexotic.com/store/c-99-shutterstat-thermostat.aspx

 

Take Care,

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Water will not damage the thermostat as most of it is already in water in the top of the radiator tank. A dunk in boiling water may damage the thermosat.  Procedure to test is to place in a pan of waterwith the portion that would be in the radiator covered with water. begin heating the water at 135 degrees F the thermostat should not expand under 14 # pressure.  At 145 degrees F, the thermostat must lift 14 #'s.  Do not test without the weight on the thermostat, it will expand too much and may cause cracks in the bellows.

 

I have a 14 chunk of brass with a small hole in the center that I sit on top of the thermostat. and then I run the test.  These thermostats were filled with a low boiling point fluid, I've been told it was ether.

 

A bad characteristic of brass is that it age hardens and gets brittle.  Usually down in the bellows a crack occurs and the fluid is lost.  There are thermostat experts that can solder the crack, drill a small hole in the thermostat and recharge and seal the hole.

 

Bob Engle

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