so just recently my truck has been getting hot when driving 60+ with the a/c on. the temp gauge creeps up past 210 and fluctuates from 210 to around 230. if i turn the a/c off it goes back down to normal temp. or if i slow down to about 50 it goes back to normal temps. ive sat in heavy traffic with the a/c on blast and the temp wont go up at all. which rules out thermostat. ive also verified temperature with my aeroforce scan gauge from my old truck. so its not going to be the gauge. coolant level is full also. the gauge cluster was completely rebuilt a few months ago.

before i get into replacing parts im going to see if it developed any air bubbles. im also thinking maybe the fan clutch could be engaged on the highway which would block some air flow to the radiator? but then why would the a/c trigger the temp to rise?

all original water pump / radiator 89k on the truck.

anyone have similar issues? or any ideas known fixes?

 

I don't think that's unusual. LSx engines run hotter than the old SBC. Unless its puking fluid, I wouldn't be too worried. Mine runs in that range in Florida and I have never had an issue. The factory gauges are not that accurate either.

TH

 

yea i know the factory gauge is way off its basically a dummy guage. ive owned a bunch of GM trucks, a procharged silverado ss, 3 2000-05 yukons a newer tahoe, and i had another h2 before this one. none of them ever had that issue which why i was wondering whats the deal. but i have noticed the H2's run hotter than any of the normal GMT 800 platform. there is no fluid leaks anywhere at all. not even the weap hole under the waterpump pulley.

 

I have an '04 sitting at just over 150k. Temps run steady at 210º until it's time to make the 5000' vertical 16-mile long climb to where I live from going to "town". Town is 4300' above sea level, home is 9000' up. If I can maintain 50-55 mph going up the mountain the temp will stay around 210-215º, but if I get slowed to the 40-45 range, temp climbs to 220-230 and stays there. Temps in town are near 100º now during the day, but the truck will still get toasty at night with temps around 80º. Radiator full, new coolant last October.

In the Debate Zone right now about whether to do a Jasper reman, trade for an '08, or find a wrecked D-Max and do a diesel build. This is my primary commute vehicle so the temp thing bothers me. With the high mileage it may just need new cooling components and a new torque converter or tranny to help it get up and down the mountain, but throwing money at this ain't appealing. If I wanted to do that I'd just buy a plane. Or a boat.

 

your issue seems normal because your under heavy load for an extended period of time. if you wanted to fix that i would say get an aftermarket electric fan or an aux coolant reservoir to help. not to mention these trucks are heavy an underpowered which puts lots of stress on the ol 6.0.

did a few experiments yesterday with my rig still not sure where to look. i was on the highway for a half hour, 20 mins with the windows / sun roof open. literally after 20 seconds of turning the a/c on the temp guage started to move a little and hoovered right on the 210 marking and a hair over. if you actually monitor the coolant temps on these trucks they usually sit around 195-205 which is normal. being that the temp gauge is very inaccurate the 210 mark is actually a little more than 210. i know this isnt an "issue", the truck is know where near overheating and im aware this condition will not cause any damage. but its definitely not supposed to hoover around 210-220 at highway speeds. driving on the highway should show the coolest driving temps because of the amount of air in the radiator.

 

H2sick,
your issue sounds normal.
but if you havent done so already, do the trans cooler mod. the radiator is sharing its cooling ability with the trans... so it will be a chore to keep temps down in the heat and long driving.
Also, the trans cooler mod helps with trans life since the radiator can leak into the trans cooler ends and then it locks up the trans

Do this and your temps well go down some and stay down.
If not, try a 160-180 degree thermo

 

Even on a 120 degree day here in AZ mine will sit with the needle straight up at the 210 mark. Either stop and go traffic or on the freeway. Your temperature fluctuating on the freeway due to increased airflow would lead me to believe you have a stuck thermostat since the coolant is being cooled faster and constantly circulated through the block instead of warming, cooling, etc to maintain the constant temp.


If 210 concerns you then go with a full aluminum radiator like a BeCool, electric fans, have the block cleaned, new water pump, more responsive thermostat, etc.

 

my first thought was stuck thermo also but what stumps me is that it only does it with the a/c on. its perfectly fine when the a/c is off. im thinking the extra heat from the a/c is getting hot faster than the thermo opens? either way its a cheap part and takes 15 minutes to install i might just throw a 180 stat in.

i had e-fans and a 40k trans cooler on my built silverado. only reason it needed the extra cooling was for track use and a 3000 stall which heated everything up. im not concerned about the temps they arnt anywhere near dangerous. but it still shouldn't be fluctuating to that extent

 

Yeah I don't think it should really fluctuate either. As mentioned, most people do an external tranny cooler as a failsafe when the stock cooler rusts away inside the radiator. That may help a little. I've had the cooler in my amazon cart for years just never pulled the trigger lol.


Curious what the new tstat does for you.

 

lol believe it or not my stock cooler isnt rusted at all. but it sucks i know its so small i dont even know if it does anything. i see the trans heat up real fast in the heat.

i ran this beast in my old silverado man did it keep the trans cold. even when it was 100+ out the trans temps wouldnt go above 160. maybe 170 if i was beating on it

transmissioncoolers.us: Tru-Cool MAX transmission cooler *No external cold weather thermal bypass


im gonna try and work on it one of these days ill let you know the result