2006 Tahoe Cooling system running to cool. 5.3L Flex

[Matt Friend]

Not to dismiss the possibility of an aftermarket radiator missing the restriction but...
Went through this when I bought mine, ended up being the coolant temp sensor. Took an IR temp gun and pointed it at the head next to the sensor and compared to scan tool reading to diag

i will give this a try and see what happens may take a day or two. Thanks for all you help this issue has been driving me crazy.

After checking the radiator it does have a restriction in the hose to the coolant tank.

 

[Mudsport96]

Not my Tahoe, but my old f150 had a similar issue. Ran cold all the time, even after changing the thermostat 3 times and the coolant sensor 2 times.

I used my turkey fryer thermometer and stuck it in the fins by the inlet neck and low and behold 195 like it should be. Even though the gauge shows cool it was fine. So its its something in the wiring or dash gauge itself. I ignore it now, but you should check with a known good mechanical gauge

 

[corvette744]

I got a 2006 Tahoe 5.3L flex that needed an engine. found a remanufactured (z code engine) had installed with new water pump, radiator and thermostat ( have replaced 3 times wit factory 178 degree stat). Now the engine runs about 165 to 175 on the road. When idling it will get up to about 210 and will stay there all day idling fans turning on and working normally. But when I drive temp drops back down to 165-175. Has anybody sean this and know what the issue might be?

I dont think the factory thermostat is a 178-mine was a 187 and thats the lowest i have seen in these engines.Is yours a t motor or a z motor.

 

[Matt Friend]

After checking the radiator it does have a restriction in the hose to the coolant tank. I am still checking for a fix for low coolant

Not to dismiss the possibility of an aftermarket radiator missing the restriction but...
Went through this when I bought mine, ended up being the coolant temp sensor. Took an IR temp gun and pointed it at the head next to the sensor and compared to scan tool reading to diag[/

I dont think the factory thermostat is a 178-mine was a 187 and thats the lowest i have seen in these engines.Is yours a t motor or a z motor.

mine is 187 also must have typed wrong.

 

[Matt Friend]

After checking the radiator it does have a restriction in the hose to the coolant tank. I am still checking for a fix for low coolant


mine is 187 also must have typed wrong.

I was out looking at it today decided to replace the water pump again just to make sure it was not my issue. Still the same. Any ideas would be helpful.

 

[ks03]

Temp gun agree with scan tool?

 

[Fless]

Temp gun agree with scan tool?

After an affirmative to that question, humor us and restrict the surge tank hose a bit to see if it improves things. What size diameter is the restriction in the radiator? How small is that hole?

 

[Matt Friend]

I did restrict the coolant hose from the radiator to surge tank and no change then I would try and restrict the return hose from the coolant surge tank to the water pump/ heater hose. Then started it up and let it run came right up to temperature about 197 degrees and then I drove it stayed around that temperature fluctuates a few degrees up and down. Not sure if this is a fix but I will drive around some and test. I’m sure I will need to adjust how much flow and see how it does. I’m still looking for a fix and other suggestions or ideas.
Thanks everyone for your advice!

 

[Fless]

Wondering if your surge tank pressure cap is sealing/working to the correct psi. Have you had it tested, or can put a known good one on it?

 

[Noggles]

I am sure this isn't it but are you sure its properly bled? I just did all new rad, hoses, pump, thermostat etc and when I first started it, it took a good 20-30 minutes of idling before it came up to full temp. It was hovering around 160-170 I believe and SLOWLY creeped up from there. Since then it warms up just fine but yeah that first time took way longer than I have experienced in other cars before.