No Heat! 91 explorer

My question is this, how can a clogged heater core cause a fluctuation in engine temp ? Not likely unless it is leaking and losing coolant. From personal experience with my 94 exploder , never over heated it ever and the same thing happened. Be prepared to replace a set of head gasket, you are going to want to do a cylinder leakdown and look for bubbles in the radiator. What is happening is the engine is slowly burning the antifreeze and on the compression stroke pushing air into the coolant passages. Some cases are so bad you can look in the overflow/expansion tank and see bubbles when the engine is at a raised rpm and warm around 2500-2800 rpm.
 
fiveohcrazy said:
quit messing around in the cold and replace the heater core!! flushing is only a temp fix anyways.......replacing it is the only way to cure your problem.
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Don't forget to mention it's only a 1/2 hour job.
 
:wink: My initial thought when I read this was a head gasket, I'll stand behind it untill proven wrong.....LOL .. I did mine in about 6 hours they are not bad to do at all....
 
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