Notorious cooling system issue

[d_rek04LSv8]

I have an 04 LS V8 that isn’t losing coolant and as long as I have the heater on the ect(F) the temp never gets over 224. When it’s not on the temp gets up to and levels off at 231(F). The fan kicks on jet mode at 225. The only system components I have not replaced is the radiator, the cooling fan and the auxiliary water pump. I’ve performed all repairs myself and have referenced the online workshop manual as well as YouTube which I have done everything I can to get it back on the road again without constantly running the heater. Luckily it’s not summertime.

 

[rgorke]

Look around the entire cooling system for any white coolant stains. Sometimes there are micro leaks that will occur. The other thing is to make sure you bleed the system with the nose of the car lower than the rear, IOWs put the rear wheels on ramps if you have to.

 

[Jiwek]

I have a gen 1 v8 and that DCCV (dual climate control valve) can cause problems. I'm guessing your fan is on normal speed and not off until the jet mode kicks in. From what I understand that jet mode is only supposed to kick on when the AC is running (maybe heat too) because it can cause the coolant to get hotter than usual. You would notice if something is wrong with the radiator unless you've been using green coolant. I think this car takes yellow coolant.

Take all of this with a bit of skepticism I am trying to help but I don't know my stuff to say with 100% confidence. Maybe wait for some other people to chime in or check out other threads with DCCV or heater valve.
Dccv dual climate control valve?

 

[SteveOwens]

The valley coolant tap to throttle body line and the degas tank are the mystery leaks because of limited visibility. They leak intermittently. You may have to drop the front bottom air duct components to observe the radiator side tanks and the aux water pump. Use of uv dye to locate the leaks may be needed. I've found the plastic cooling system parts keep you under the hood than behind the wheel. I was lucky to find a machinist to make me three sets of the engine cooling piping. i have one set installed with zero issues awaiting rework aluminum degas tanks. I found Ron Davis racing makes custom rads with one i had made with my oe example to used for ref if you choose that route. My oe rad lasted 310k before the plastic tank let go. I used the hyd resevoir as a oil catch can with the crankcase ventilation reroute in a effort to keep the intake manifold & cats oil free.

 

[04_Sport_LS]

I'm guessing your fan is on normal speed and not off until the jet mode kicks in.

It's called "failsafe mode". Normal speed (as you put it) is exactly that. (Normal speed). The "jet mode" is fan running full speed, and does its best to hold the temp at 230F.

 

[04_Sport_LS]

It's called "failsafe mode". Normal speed (as you put it) is exactly that. (Normal speed). The "jet mode" is fan running full speed, and does its best to hold the temp at 230F. to keep the engine from toasting itself.