Hey guys,
Quick question about a bad t-stat, if it was stuck closed and the coolant was unable to flow correctly would the top rad has lots of pressure? I checked the lower and it was cool and soft which would tell me the thermastat is not letting the coolant pass thru. I
have temps @ 250º (Ultraguauge) which I shut it off right away. I let off the pressure refill and go again.
Have any of you had this issue and what was your solution

 

You got to 250? I'm surprised your head gaskets didnt go.

 

They did, or the cracked block, one is allowing exhaust gas to pressurize the cooling system. Stop driving until sorted out. Temps should stay under 212 on the highway. There is a chemical test you can buy that checks coolant for exhaust gas and the test liquid changes color. May be hearing bubbles rushing thru pipes under dash.

Now think about the D2 coolant system, if the top hose was rock hard, and the lower hose was soft, the stat is after the lower hose. So it may be the clogged radiator also,...

 

Hey Savannah
After we got home I looked at the cooling system map and came to the same conclusion about a clogged rad. It makes more sense and when I checked it this morning the system is cold but still under pressure. When I released the rad cap the pressure bled off and
coolant poured out the overflow tube on the expansion tank. As for the temps, the Ultragauge was showing 198º and steadly rise then spike extremely fast to 250º which by then I had shut it off. I do not think its a cracked head as these heads were on another one of our engines that lost the front timing cover gasket and wiped out the crank bearings with diluted oil.

 

What year is your truck, have you ever replaced the t/stat with a 180 degree soft spring, how about the radiator has it ever been replaced.
For now, don't drive the Disco till you find the answer. If need be do a coolant pressure test and a chemical block test.

 

Its a 1999.5 and I used a stock temp stat which is new but is most likely a offshore piece. The rad is the original one and should be replaced. We just price out a new rad, 180 stat and new lower rad hose from Rimmwer Bros and hope to place the order later today. The truck was on a temp insured plate to shake out the bugs so no more driving till this is resolved.