2006 Tahoe Cooling system running to cool. 5.3L Flex

[Matt Friend]

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?

I will have it tested my pressure tester will not test that type of cap good idea. Thanks

 

[Matt Friend]

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.

After the engine was replaced I would top off surge tank after each test drive( if needed) and I have put over 2k miles on sense this started. I also got a fill funnel that helped. See attached

 

[Noggles]

After the engine was replaced I would top off surge tank after each test drive( if needed) and I have put over 2k miles on sense this started. I also got a fill funnel that helped. See attached

View attachment 279433

Shoot I didn't even do all that. I just filled the expansion tank to the seam and made sure it stayed there. I am curious what is causing this now..

 

[livingez_123]

If you are running E85 it does tend to run a bit cooler. I've seen up to 20° cooler.

 

[Matt Friend]

If you are running E85 it does tend to run a bit cooler. I've seen up to 20° cooler.

I have never run e85 in this engine not sure if it runs cooler.

 

[Dantheman1540]

Why is it so concerning that it's running cooler? I purposely installed a 160* thermostat and enjoy seeing my engine stay between 160-170* during cruising. I still get 2mpg better than the typical 6.0 NBS SUV and when towing it stays considerably cooler when pulling up long hills.

 

[Matt Friend]

After reviewing all that I have done with cooling system I believe that the restr

If your radiator was replaced, you might be missing the restrictor in the hose from the rad to the surge tank. Without that restriction, these engines will run too cool. The lower thermostat doesn't help, either.

Why is it so concerning that it's running cooler? I purposely installed a 160* thermostat and enjoy seeing my engine stay between 160-170* during cruising. I still get 2mpg better than the typical 6.0 NBS SUV and when towing it stays considerably cooler when pulling up long hills.

well with a remanufactured engine the rings and cylinder walls won’t wear and seat to each other and could cause the engine to use oil and have excess blow by. It is also to help with fuel mileage but sounds like your mileage got better. The thermostat will not open with the temperature so low.

 

[Dantheman1540]

After reviewing all that I have done with cooling system I believe that the restr


well with a remanufactured engine the rings and cylinder walls won’t wear and seat to each other and could cause the engine to use oil and have excess blow by. It is also to help with fuel mileage but sounds like your mileage got better. The thermostat will not open with the temperature so low.

Not a bad point about the engine wearing slowly or not as properly, however. In my case, I can easily get it up to temp sitting idling in traffic or in the garage where there is minimal airflow, even when the fans kick on the coolant temp rises to 200ish. It just takes a little longer to climb and has a faster recovery.

Of course another good point might be winter weather but I don't have to worry about that in Fl and mostly did the lower thermostat to keep a little more heat away from the AC condenser when its 110* out.

 

[Matt Friend]

I do live where we have winter and snow. Will need the heater to get hot. Thanks for your help.

 

[Matt Friend]

If your radiator was replaced, you might be missing the restrictor in the hose from the rad to the surge tank. Without that restriction, these engines will run too cool. The lower thermostat doesn't help, either.

Well you were right I went back and plugged the hose to the surge tank again and the temperature came right up and after I had check the restrictor in the radiator it must be to large I put a shut off in the fill hose from radiator to surge tank. Now I can control the flow and it seam to be working fine temperature is running about 197-201. I should have given it more time when I tested it the first time. Thanks to everyone that helped with this issue. I’ll update if anything changes.