6.9 pushing coolant

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Mar 14, 2012 | 01:08 PM

mcfarland123

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6.9 pushing coolant

anybody have an idea of why 6.9 is pushing coolant out of overflow when going down the road but not at idle?

Mar 14, 2012 | 01:23 PM

joshofalltrades

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well how much is it pushing out? does it suck it back in when it cools? its normal for this or any engine to push some coolant over there as it heats up, then suck it back in as it cools.
if your radiator cap is bad, it will push more coolant over there than it should and leave the cooling system with no pressure. the easiest test for this is to squeeze the upper rad hose while the engine is hot. it should contain enough pressure to be hard. if its soft and/or you hear coolant moving to the overflow tank as you squeeze it, you need a new cap.

Mar 14, 2012 | 01:32 PM

mcfarland123

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it will push out agout 2 gallons on a 40 mile drive. it never sucks it back in. tried new cap & thermostate.

Mar 14, 2012 | 01:40 PM

joshofalltrades

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possibly a head gasket problem, you should confirm this by buying a "coolant leak indicator" fluid from your local parts store, just pour it in the radiator and drive a bit, then see if it turned the color that shows a problem.

Mar 14, 2012 | 01:46 PM

mcfarland123

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ok. i will try that. thanks

Mar 15, 2012 | 03:48 PM

hairyboxnoogle

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Head gasket or cavitation it sounds like. since it doesnt do it under load im leaning towards cavitation, hopefully you get lucky and its the gasket.

Mar 15, 2012 | 04:43 PM

38Chevy454

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Quote:

Originally Posted by joshofalltrades

The kits I am familiar with are known as "block checker" or "coolant test" kits. They have a fluid, but you do not put it in the coolant, instead you suck the vapors, off the top of the coolant in the radiator, through the fluid and if you have hydrocarbons in the coolant it changes color.

I have to agree with the others that if you are blowing out 2 gallons of coolant and your cap is good shape, then you are getting pressurization into the coolant form the combustion chamber. Either head gasket or bad cavitation. Hope for head gasket as that can be replaced and use your engine more. If cavitation then unfortunately time for a new engine.