Need Help. 2011 Tahoe cooling system will not pressurize.

[Joseph Thomas]

As long as the system holds pressure when tested, I wouldn't worry about whether or not the hoses feel hard/pressurized while running.

My radiator hoses will feel either soft or hard depending on when I feel them. The thermostat being open or closed will play a big part in that also.

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I understand that, but if the system cannot pressurize itself and maintain pressure, then there is something wrong. Also, there is the heat issue too.

 

[Joseph Thomas]

I've been out for a couple of days so I finally got around to Burping the system. I used the proper Lisle Funnel. I am located in Central Texas and we have been hit with a winter/ice storm. My Tahoe was cover in ice and today it is 27 degrees here. I stated the Burp process, but she could not get up to operating temperature for the thermostat to open. I let her idle for about 35 min and the temp stopped rising at about 195 degrees. I guess its just too cold here. During those 35 min, I did not see any air bubbles rise in the funnel. I will try again on Tuesday when it warms up and this storm passes.

 

[gooffeyguy]

I understand that, but if the system cannot pressurize itself and maintain pressure, then there is something wrong. Also, there is the heat issue too.

I understand that, but if the system cannot pressurize itself and maintain pressure, then there is something wrong. Also, there is the heat issue too.

Could be the water pump. I recently replaced the water pump on my 2001 because it was leaking coolant. When I pulled the water pump off, the internal vanes had basically disintegrated. I would think this could cause it to not build pressure

 

[Larryjb]

Have you considered the blend door in the HVAC? If the blend door is stuck on the cold side, your coolant may be up to temperature but the air is not being directed over the heater core, therefore cold air.

 

[Larryjb]

Could be the water pump. I recently replaced the water pump on my 2001 because it was leaking coolant. When I pulled the water pump off, the internal vanes had basically disintegrated. I would think this could cause it to not build pressure

I could be wrong, but I would think if his water pump were that bad he'd have an overheating problem.

Pressure is built up mainly by heat, not by the water pump circulating the coolant. When you stop the motor, the system will still remain at 20psi until the system cools.

Don't our radiators have restrictors in line with the radiator? This could account for a higher pressure of water in the radiator and a lower pressure on the water pump inlet hose, which would account for why you could squeeze the lower radiator hose by hand. When you put the tester on, the 20 psi would have been equal throughout the system.

 

[gooffeyguy]

I could be wrong, but I would think if his water pump were that bad he'd have an overheating problem.

Pressure is built up mainly by heat, not by the water pump circulating the coolant. When you stop the motor, the system will still remain at 20psi until the system cools.

Don't our radiators have restrictors in line with the radiator? This could account for a higher pressure of water in the radiator and a lower pressure on the water pump inlet hose, which would account for why you could squeeze the lower radiator hose by hand. When you put the tester on, the 20 psi would have been equal throughout the system.

That makes sense

 

[Joseph Thomas]

Could be the water pump. I recently replaced the water pump on my 2001 because it was leaking coolant. When I pulled the water pump off, the internal vanes had basically disintegrated. I would think this could cause it to not build pressure

Yeah, that is what I'm thinking. However, I don't have any leaks. If the Burp process doesn't work, I may be replacing the water pump anyway.

 

[BG1988]

I've been out for a couple of days so I finally got around to Burping the system. I used the proper Lisle Funnel. I am located in Central Texas and we have been hit with a winter/ice storm. My Tahoe was cover in ice and today it is 27 degrees here. I stated the Burp process, but she could not get up to operating temperature for the thermostat to open. I let her idle for about 35 min and the temp stopped rising at about 195 degrees. I guess its just too cold here. During those 35 min, I did not see any air bubbles rise in the funnel. I will try again on Tuesday when it warms up and this storm passes.

disconnect the fan relays but do watch the temps(it might check engine though don't worry just watch the temps) don't forget to reconnect the fans and cool off the engine with it running...

if you have an aluminium block don't attempt this... as it may cause damage...


that is totally false it should come up to temp without issue.... no one else with a GMT900 that lives in a cold area has that issue..

t-stat is broken or slow and starting to fail...

 

[Foggy]

Just as an FYI: the factory temp gauge is VERY Vague...
It will show 210* - the middle normal operating temps -
All the way from about 185* - 220* ish...
Best to put a scan tool of some sort to see the ACTUAL Coolant Temps
when diagnosing these type of issues.
I was rather surprised several years ago when I put my scanner on
a GMT900... They are ALL the same... It's so the soccer moms don't freak out

 

[shoplizard]

Have you checked the HVAC system for fault codes, I am assuming your Denali has auto HVAC and therefore can be accessed by a scan tool. For the most part, what you are describing is normal operation, the cooling system will not build pressure until the engine temperature exceeds the boiling point of water or the coolant which at your altitude is above 195f which is the opening temp of the thermostat. The fact that you say the HVAC will blow hot air at a high temp setting tells me the engine portion is ok. There may a problem with the HVAC not controlling the temp accurately. This could be a faulty temp sensor in one of the ducts or an issue with the controller. When you increase the interior temp and then change to a much lower temp the HVAC will attempt to cool back down by lowering the outlet air temp to adjust to your new temp setting. This could be more noticeable with the lower outside temperatures. Good luck