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Old 03-05-2024, 11:36 AM
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ta6point6 ta6point6 is offline
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Default Pressure in overflow tank cold=bad head gasket????

So I had the 6.0 replaced in Avalanche in December due to spun cam bearing. So it started with a leaking upper radiator hose, no big deal tighten up the clamp. Then leaked again and took in to mechanic and freeze plug was loose. Keep losing fluid due to loose upper radiator clamp I thought. Temperature has been a tick above normal nothing in 240 range. What else causes pressure in coolant system while cold and cause leaking coolant in upper radiator hose?

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Old 03-08-2024, 10:20 AM
mgarblik mgarblik is offline
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Quote:
Originally Posted by ta6point6 View Post
So I had the 6.0 replaced in Avalanche in December due to spun cam bearing. So it started with a leaking upper radiator hose, no big deal tighten up the clamp. Then leaked again and took in to mechanic and freeze plug was loose. Keep losing fluid due to loose upper radiator clamp I thought. Temperature has been a tick above normal nothing in 240 range. What else causes pressure in coolant system while cold and cause leaking coolant in upper radiator hose?
I can't explain your upper hose leak unless it's not the hose. Remove it from the neck and VERY carefully inspect the neck area which I suspect is plastic. If you don't find any defects in the neck or hose, try a constant pressure style hose clamp, (a spring clamp) vs a worm screw clamp. They generally work better on plastic necks. This would be an OE style clamp.

It is not unusual for a surge style reservoir to maintain pressure even cold. This is what an Avalanche would have, with the pressure cap on the plastic surge tank. I have seen them hold some pressure overnight. (small amount).

For peace of mind with your replacement engine, you might want to perform a combustion leak detection test on the truck. This is a kit you can buy with a color changing hydrocarbon detecting chemical you put in a tube and "sniff" the vapor on a hot engine in the surge tank. If there is combustion gas in the coolant, the dye will change from blue to yellow/light green. It is a foolproof test for a failed head gasket, cracked block or head. I will provide a link for the tool. NAPA and other real parts stores sell these.


Link for tester: https://www.amazon.com/Block-Tester-...A1810GNA3P38E9

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Old 03-08-2024, 12:54 PM
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ta6point6 ta6point6 is offline
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Thanks for the reply I just wanted to give the mechanic something to go on when I took it back to them. I do not have a lot of confidence in the place that did the engine swap. I only took it to them because it was just down the street for me. Finding a good mechanic is like finding a good doctor it is hard to do. I told them I suspected a bad head gasket and the test you mentioned. They did the test and said there is presence of hydrocarbons so with head or cracked block. I am still waiting to hear back what the engine builder is supposed to do next. I dont think there is much of a decision, replace the motor. If he rebuilt a motor with a cracked block then not sure they are a good engine builder anyway.

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Old 03-08-2024, 05:32 PM
mgarblik mgarblik is offline
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Sorry to hear you kind of have a worst case result. I don't know the condition or value of your truck, but I have had my best luck with a low mileage used junk yard engine vs a rebuilt engine from some lousy re-builder. The factory usually did a good job originally. Might want to do a search on car-part.com and just see what's out there. LS engines are in pretty high demand so it could be hard to find one. Best of luck with it.

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