I have a 2003 discoII with 136000 miles on it. I have no heat and an over heating problem. There are no coolant leaks and I replaced the thermostat and the expansion tank cap but it did not help. Temperature at idle stays where it should be no matter how long I let it idle but the outside temp is currently in the single digits. The top coolant hoses, the coolant in the expansion tank and the smaller hose going to the underside of the expansion tank are all very hot. The hose from the bottom of the radiator is ice cold and the 2 lines going to the heater are also cold. Is it the water pump? I don't see any leaks from it.

 

Tuern the truck off and feel the radiator, is it hot?
I would have to say either a bad water pump or a clogged radiator.
If I remember right the water pump pumps water from the pump directly to the heater core, if that is the case then I would say that the impeller went bad on the pump.
I assume that your belt is still good?

 

I put a new belt on this past summer. I just went and started it up again and all of a sudden it is working fine. I had recently had a small leak from one of the lines that goes to the throttle plate but it wasn't much of a leak and I replaced the cracked line. I'm hoping it was just an air bubble from when it was leaking. I tried bleeding the system after driving a few miles just to be safe and there was a small purge of air then only coolant so I am hoping that all is well now. I wouldn't think that a water pump could start working again if the problem had been caused by a faulty pump. Or could it?

 

you would probbably hear it if the pump was going

 

Your truck won't fix itself in this case.
Do you know how to bleed your coolant system?

 

It overheated again last night. I tried opening hat looked like a bleeder screw on the top radiator hose. With the engine running a little air came out and then coolant. It still over heats. Do I need to do it again??.

 

You only bleed the coolant system with a stone cold engine and not while idling.

 

Thanks for your help. I will give it a try.