replaced my thermostat couple weeks ago, i flushed the system and put the green antifreeze back in. Now the heater doesn't blow air out as hot as it did before. temp runs about 175-180 nothing on that has changed.

just put a thread on the interrior section i think...couple good ideas from people

ok thanks

Someone PM'ed me about just that. Here's the copy.


I learned a long time ago to boil test all my T-stats when a replacement set doesn't cure the "underheat" issues.
I had a 6.2 that took "seven" T-stats before I got one to let me have 190 all the time.

Take you old stats and your new ones, throw 'em in a pot of water and heat it up, with a thermometer in the water. On a 195 stat, they should begin to open around 190ish and are fully open by 195. Then cool 'em down. They should be fully closed by 190 again. Pick the two that are closest...


Where I buy them seems to make a difference in whether they are properly calibrated at assembly. From the dealer, I can't remember the last time I got one that was off. Napa is about spot on 70% of the time. My single stat 5.9 cummins are the pickiest. My F800w/ a 5.9 eats 'em about every year and half. Some run it hot, and some run it cold, when they begin to perform poorly.
I've got a Yanmar here that is on stat #4, and it still runs hot. Every time I test the stat new, they work great. Throw it in and within a day, it overheats. Take it out, and, sure enough, it sticks in the closed position when testing.

moved to interior

Someone PM'ed me about just that. Here's the copy.


haha that was me. but to the OP, duramaxs take the orange coolant...

replaced my thermostat couple weeks ago, i flushed the system and put the green antifreeze back in. Now the heater doesn't blow air out as hot as it did before. temp runs about 175-180 nothing on that has changed.

You said thermostat,but there are 2 of them,a 180* and a 185*.Also,as the last post said,the Dmax takes the orange Dexcool type antifreeze,not the green.

X2, back to the drawing board. ;)