When towing with my lly it keeps blowing out coolant, dealer trying to tell me it's the thermostat, I think it's head gsk, any suggestions:cool:

I doubt its the thermostat(s). Sure sounds like tel tale head gasket issue to me.

First thing you want to check is the rad cap, Why would you take it to someone and then dought there findings! If the cap is OK then thermostats would be a good thought. I take it that they did not find it blowing bubbles, it was boiling in the heads and blowing out coolant. Your antifreeze needs to be checked also.

If the head gasket was gone, you would see the problem at idle, just rev the engine to get some water pressure.

If it is thermostat then as the engine heats up, and the thermostat opens, it might leak around the thermostat housing.

Should be able to rule out head gasket pretty fast IMHO.

cheers, Steve

When towing with my lly it keeps blowing out coolant, dealer trying to tell me it's the thermostat, I think it's head gsk, any suggestions:cool:

Let's be realistic.

keeps blowing out coolant = 99.9% head gasket blown.

.1% = stuck thermostats causing overheating (fat chance!).

Check the upper rad hose when the engine is cold, as in the morning after it has cooled completely, or in the parking lot after work. If the hose has pressure in it, then there is a compression source making its way into the cooling system. You will be able to tell if it has pressure, you should easily be able to squeeze the hose and make opposite sides touch with one hand using just your thumb and a couple of fingers. If you cannot, well . . .. . . . 99.9% :(

Let's be realistic.

keeps blowing out coolant = 99.9% head gasket blown.

.1% = stuck thermostats causing overheating (fat chance!).

Check the upper rad hose when the engine is cold, as in the morning after it has cooled completely, or in the parking lot after work. If the hose has pressure in it, then there is a compression source making its way into the cooling system. You will be able to tell if it has pressure, you should easily be able to squeeze the hose and make opposite sides touch with one hand using just your thumb and a couple of fingers. If you cannot, well . . .. . . . 99.9% :(

X2... hope for the best, test for the worst. It's pretty straight-forward...

My truck sometimes does it on warm up if its left at idle to long the temp gauge gets to around 180 and stops climbing then out comes the coolant!
Now...If its driven after a short warm up it never does it, if I park it after full warm up it will sit and idle forever and doesnt puke, I think it's a stat (but) I do have pessure in the hose (system) when cold?????????

i for one have never seen or heard for that matter of a tsat, causing coolant to piss out overflow. Follow the steps as already stated. if someone with a lil more knowledge please pm with how this could even possibly be a tsat that would be much appreciated. Good luck....hope it is somthin easier on ur pocket

Yes, it does sound like it is the head gasket. I see you have several mods with the truck- Did you take it to the dealer with those on?

Be careful that you don't overfill the coolant reservor- coolant expands when hot and has to go somewhere- that is what the coolant tank is for. If it is filled to the top, it will puke out coolant out when hot.:D

Let's be realistic.

keeps blowing out coolant = 99.9% head gasket blown.

.1% = stuck thermostats causing overheating (fat chance!).

Check the upper rad hose when the engine is cold, as in the morning after it has cooled completely, or in the parking lot after work. If the hose has pressure in it, then there is a compression source making its way into the cooling system. You will be able to tell if it has pressure, you should easily be able to squeeze the hose and make opposite sides touch with one hand using just your thumb and a couple of fingers. If you cannot, well . . .. . . . 99.9% :(


X3. That's what I did, and that's what I had to have fixed. Upper rad hose was hard as a rock after sitting over night. Covered under warrenty. It only cost me a $100. And that was with all the mods I have in my sig. I was lucky and found a good dealer.

i for one have never seen or heard for that matter of a tsat, causing coolant to piss out overflow. Follow the steps as already stated. if someone with a lil more knowledge please pm with how this could even possibly be a tsat that would be much appreciated. Good luck....hope it is somthin easier on ur pocket
YOU never saw an overheating engine, thermostat or otherwise piss out of the coolant tank? How could that be? These are pressurized tanks not like the old ones which were just expansion tanks.

My wifes minivan had a head gasket blow , you could let it sit and idle in the driveway for an hour and nothing , as soon as you took it on the highway that was it , antifreeze everywhere.Hope thats not your problem but sure sounds like it.

I think most people on this site would doubt what the dealerships tell them. I know there is some very good GM technicians out there, but they are few and far between with experience with the duramax. Just look at all the posts with horror stories about possible headgasket problems. My friends truck was down for 2 months to get headgaskets replaced. This was after 3 dealerships said there was no problems with the heads/gaskets.

I have only seen problems with the rad caps creating a vacuum overnight causing the upper rad hose to collapse. I would say your truck has a headgasket problem!

They replaced t/stats, said there was likely a pressure buildup due to sudden increase in temp and the stats were sticking causing a pressure spike over 15 psi therfore blowing coolant, there is a pile of crap!! I just agreed and said i'll be back when i finish it off!! Now i'll start throwing some boost and heat at it LOL!!