Engine temp not constant

1992 PONTIAC TRANSPORT
192,000 MILES
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DMNOVAK
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Replaced thermostat, coolant sensor, radiator fan and fan harness and fan relay, doesn't seem as if thermostat is opening as it should. Thought day old thermostat was bad but 2nd new one doing the same thing
Aug 12, 2012 at 9:05 PM
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KHLOW2008
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What do you mean by not constant?

Do you have coolant losses issues?
Aug 12, 2012 at 9:14 PM
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DMNOVAK
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No coolant loss,thermostat doesn't open all the time upper hose hard as a rock when it doesn't open.
Aug 12, 2012 at 10:37 PM
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ASEMASTER6371
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how badly did it overheat and how many times??

Roy
Aug 12, 2012 at 10:45 PM
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DJCL
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You should check to see if the head gasket is leaking. Get a block test kit
Aug 12, 2012 at 10:48 PM
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DMNOVAK
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Caught the overheating(once)in time head gaskets replaced 10000 miles ago
Aug 12, 2012 at 11:06 PM
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KHLOW2008
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Is the replacement thermostat OEM? I believe you should be looking at it one more time.
Aug 13, 2012 at 1:14 PM
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DMNOVAK
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Why OEM
Aug 13, 2012 at 2:01 PM
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KHLOW2008
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Quality of thermostat matters.
Aug 13, 2012 at 4:31 PM
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DMNOVAK
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Ok thx I will get an OEM
Aug 13, 2012 at 5:38 PM
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MIKE H R
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even new thermastats can be bad right out of the box. Would get a OEM like KILlow says. It may also cause the temp sending unit to mess up. check any wires. After replacing the thermastat check the guage if it still does it the sending unit could be going bad.
Aug 17, 2012 at 2:36 PM