@Disel I drilled a small 1/8" bypass hole in my inline thermostat, temp is perfect, no spikes now that the coolant is flowing @NFS Idk if an inline t-stat will be a fix for you since there are so many different things that can go wrong with the cooling system, mine just happened to be the thermostat. Even looking at the service records from the previous owner, he's been complaining about engine running hotter than before ever since he had the t-stat replaced.

Here's what I think was happening, and again I am no expert in Engine Cooling System clearlyand should probably do more research. Having the OEM 195F t-stat was just a bit too restrictive. Removing the t-stat all together was also detrimental to the cooling process especially on the highway with higher RPMs, given that our pump is belt driven, coolant flowed just a bit too quickly for proper heat transfer.. Adding the inline t-stat helped restrict the flow just enough that coolant is able to reject heat at the radiator before making its way back into the engine. This could have worked at the original location too but not with a 195F t-stat. Also original location sucked. With the inline I was able to take the t-stat out today and drill a small hole in matter of 15min, didn't have to drain coolant, didn't have to take the wheel and fender liner off, didn't have to scrape my arms trying to get to the darn bolt.

Again this is just my experience and opinion, it worked for me may or may not work for you.

Also worth mentioning, larger diameter top hose may be detrimental too. Top hose is generally smaller in diameter than the lower hose. Higher coolant flow does not equal better cooling. Just a thought, again I am no expert in Engine Cooling Systems, just throwing some ideas out there. Here's a principal that may be worth considering here: Laminar Flow

 

Bingo. Finally sunk in? Pretty much the same for every water cooled vehicle made.

When it is HOT outside, your coolant will be a higher temp, but still be normal for extreme heat.

 

Sure, but still there are other vehicles on the road that don't run this warm even when it's 115F outside. Does that mean the H3 has poorly designed cooling system?

 

Updates

so I did the relocating thermostats mod and I put 160f thermostats in there . Everything seems to be within range and cooler .
today is 100 degrees and mine little over half while before it would go past the 3/4 or at 3/4

another weird question and that may be normal for hummers but I don’t know

why when I turn the heater on . The car temperature drop to like 180 at idle which is perfect on the same 100degree weather

and if I turn on the ac then I am at idle 206f or around that! At the same 100 degree weather


and when both are off I am at like 200F at idle on same 100 degree weather !

is that normal ? I thought the ac and heat have nothing to do with engine coolant temperature ?

also regardless which one when I drive the temperature go up a little too, is that normal ?

 

There's a radiator(AKA:>heater core) inside the hvac case.

 

The quality of the fan also affects the cooling efficiency. I read that the Italian SPAL are good in performance. But maybe there are alternative manufacturers?

 

I am confused how that video is answering my questions above?

 

Radiators & heater cores have fins built in, for air to pass through & transfer the heat!

 

oh okay but what about when ac is on and when both are off??? You answered 1 out of the 3 lol

 

Q&A?