I have been having the usual disappearing coolant and today I hit the interstate after driving for a couple hours around town. I stopped and shut down for fuel and wasn't a mile down the interstate before it overheated. Pulled over and shut down and let it sit for a while. Got back to a gas station and cooled it back down, completely refilled the coolant properly and blead the system out. Hit the road and was overheated within a mile. I got it towed and I pulled out the Tstat and poured boiling water into it and it opened allowing a fair amount of water to pass through. It wasn't free flowing but it was passing through. Re-blead and filled the system. It idles at normal temp with the cap OFF. Replace the cap and the pressure starts to build and starts heating up. Remove cap and burn face. It's explosive like "Old Faithful" and then the lines begin to de-pressurize and the temp comes down. Any idea's would be great because I am stuck out of town and am really in no place to start tearing down the engine and replacing gaskets. I have not seen any fluid what-so-ever from the block or anywhere around the heads. Why would the 2 top coolant lines only build up pressure with the cap on? Very mild heat coming from the vents on HI heat wide open.

 

Try it with the Tstat out.
If it still build pressure that fast it may be a gasket leak - motor pumping gas into your cooling system.
________
Emili_

 

Yeah, it sounds like the headgasket is gone.

 

How can I run it without the Tstat. The Tstat is that 3 way heart with the thermostat down inside the plastic housing to the passenger side of the the engine behind the radiator. How can I run without that? I know I used to do it with block mounted tstat's on Jeeps but this thing has three lines into it. Can I get inside and destroy the guts and dig them out or do I need to fabricate something. I thought of getting a drill and drilling out some big holes through it to see if that would work. I can try to find a replacement part but if I can get back home having removed the Tstat that would be great. Can you tell me how to run it without the Tstat installed?

 

Sorry I didn't realise it was a DII.

But it does sound like your moter is pressurising the cooling system.

maybe your head gasket, in which case taking out the Tstat wouldn't help.
________
Marijuana Bubbler

 

Cobb try refilling it with the engine cold, with the lid off the expansion tank start the truck and see if it still explodes out. If it does you have other problems like head gaskets. A hot engine with pressure will generally blow up like that, hence the warning labels on the cover. It is not uncommon to get a bad t-stat, especially an aftermarket one.

 

Cap might have gone bad. It is suppose to release pressure when it gets too high. How far away from home are you ????

f you're nowhere near a dealership or Rover parts place, I think I'd buy a gallon of coolant and try running with the cap off. But that is from someone that never faced that situation, so not sure if its feasable or not.

good luck! let us know how this turns out.

 

PM me your number and I'll call you. There is no short term fix for this. If you are lucky you haven't toasted the engine yet, do not drive it for any reason.

 

Apart from the obvious head gasket blown this may also be caused by a completely blocked radiator core. If the motor is at operating temp and the center of the rad is cold then you have a blocked core.

 

I am 3 hours from home all interstate. When I have the radiator cap off I can hold the RPM's up or let it idle and the temperature will not go above normal operating temp. It's only when I close the cap do I get the pressure and temp rise. When I say it's explosive, I mean that I had to search all over the place to find my cap after it blew up hit the underside of the hood and deflected about 10 in front of the truck and bounced it off another car.

And sorry for not letting you know but I have a 2004 Disco II S model with just over 105K on it..