2005 Chevy Silverado Coolant hot

2005 CHEVROLET SILVERADO
52,000 MILES • V8 • 4WD • AUTOMATIC
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SPEEDSTARV
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Last month I get the "engine coolant hot" message. I checked everything over and find only that the coolant was low, but the system still had a lot of pressure after 7 hours of sitting idle. I had a mechanic check it over. No signs anywhere of drips, leaks, stains, no smoke, no smells. I replaced the thermostat and checked all hoses.
Today, I get the message and the engine started to overheat. Again, no signs. This time, no pressure when I popped the rad cap. After lots of researching, there's no coolant in my oil or smoke, so I do not believe a gasket or cylinder head to be the issue. I did read that there may be a possibility of a "pinhole" at the waterpump and cooloant is burning off the hot engine, but still.. no signs of a leak? Really frustrating.
Where else should I look?
Nov 21, 2008 at 12:24 PM
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MMPRINCE4000
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Have a compression test performed to eliminate the head gaskets.
Generally it is either leaking it or burning it.

If compression is OK, I would replace the waterpump.
Nov 21, 2008 at 5:20 PM
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DENNYP
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I normally see the water pump to engine block gaskets fail. The coolant leaks out and burns off, or will only leak at certain temperatures. I have also found coolant resivoir caps leaking coolant.
Nov 21, 2008 at 10:29 PM
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SPEEDSTARV
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[quote:e99fb187ef="mmprince4000"]Have a compression test performed to eliminate the head gaskets.
Generally it is either leaking it or burning it.

If compression is OK, I would replace the waterpump.[/quote:e99fb187ef]

Compression test was fine. Still going through coolant. GM mechanic advised to flush dexcool and use new "universal" coolant. Flushed system and replaced thermostat. Still having same issue.. every 5-6 weeks, coolant is low and coolant hot message comes up on dash.
Apr 28, 2009 at 3:37 PM
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DENNYP
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[quote:55ac072cab="dennyp"]I normally see the water pump to engine block gaskets fail. The coolant leaks out and burns off, or will only leak at certain temperatures. I have also found coolant resivoir caps leaking coolant.[/quote:55ac072cab]


Have you checked this yet? You might also want to consider having a coolant system pressure test done. As for the flush, that will have nothing to do with coolant loss. As for the universal coolant, that will have no bearing on the loss of coolant.
Apr 28, 2009 at 4:05 PM
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SPEEDSTARV
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[quote:786dc1add3="dennyp"][quote:786dc1add3="dennyp"]I normally see the water pump to engine block gaskets fail. The coolant leaks out and burns off, or will only leak at certain temperatures. I have also found coolant resivoir caps leaking coolant.[/quote:786dc1add3]


Have you checked this yet? You might also want to consider having a coolant system pressure test done. As for the flush, that will have nothing to do with coolant loss. As for the universal coolant, that will have no bearing on the loss of coolant.[/quote:786dc1add3]

Coolant pressure test revealed no leaks at all. Replaced the coolant reservoir cap already. That hasn't helped. The GM mechanic stated that they would replace the entire water pump assembly and its still a 50/50 shot in the dark. I guess I will try replacing the pump and gaskets......
Apr 28, 2009 at 5:56 PM