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Temp guage spike

May 16 2017 at 6:00 AM
Bob  (Login cool67)
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I have a fresh SBF crate motor in a project.Dakota Digital dash (It id a direct replacement for all the guages,fuel, temp ,oil, tach, speedo, turn signal etc). All in one panel.Motor broke in fine. Anyway for the first time I had the motor running at an "idle" for awhile and the temp went to about 185 then dropped to about 170 then immediately spiked to 230 plus. The waterpump is new, thermostat new, new alum radiator,no elec.fan just mech.one Actually I replace everything when I restore a car. So where should I start. I was thinking thermostat....try a temporary mech.temp guage to see if it was really that iratic.....electric fan or?

 
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Gerry
(Login gerryproctor)
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Validate the reading first.

May 16 2017, 6:15 AM 

If the gauge is accurate, this behavior is common to an air lock. These usually clear themselves if they have a clear pathway to purge. Remove the radiator cap and run the engine up to thermostat opening temperature, then elevate the engine speed to around 2k rpm and observe coolant flow in the radiator. If their was an air lock, you'll start with a full radiator and once the engine burps, the coolant level will drop so be prepared to keep it topped off. It also makes a difference if you're running an expansion tank to recover the coolant and maintain and fully topped up radiator.

 
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