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Boiling Coolant?


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Run the truck for 10 minutes and the coolant starts to boil off. There is no thermostat. It happens with the radiator cap off as well. Water pump is dead? Is there any other possibility? No smoke from the tail pipe, and the oil looks clean as well. Thanks for any input you can give me.

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put the thermostat in it to, i've never seen it, but all the old guys tell me without t stats they can overheat, the coolant is constantly cycling, and never stays in the radiator long enough to disipate heat is the theory.

 

get the simple stuff in order, t stat, cap, coolant level and mixture, and go from there.

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The reason modern automotive cooling systems have pressure caps is to raise the temperature at which the coolant boils. Leaving the cap off, or running a cap that doesn't provide a positive seal, is just about guaranteed to boil off the coolant.

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Just to keep us all on the same page -- is this in regard to the 86 MJ listed in your signature? So it actually has a radiator cap and catch bottle, not the pressurized bottle found on the 87 - 90 4.0L models?

 

2.5L or 2.8L?

 

How old is the radiator?

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