ok i have a 1997 chevy express cut away van with a 6.5 diesel engine . i have a new injector pump new radiator new water pump new thermostates and a new fan clutch and new tank cap . everything is nice and cool and i drive it alot of miles a week without problems but today as i was getting off the highway the temp went up over the 210 mark and it burped a little coolant out of the expantion tank. i drove it another 1/8 mile after i got off the exit ramp and the temp went back down . so i pulled into a parking lot and the tank was leaking and lost maybe 6 ounces if that . now i drive it another 50 miles in the city and the temp never went 2 little lines above the first full line and i have good heat. the heat does drop off when im sitting at a light but goes back to a nice heat when im driving.. people are saying head gasket but im not losing any coolant it doesnt over heat and its been 5 months since i put all the new parts on the engine. it only did it this time when i got off the freeway i have a friend that runs race cars said sounds like the pump is spinning to fast thru the engine and isnt cooling it the right way? any help would be great

 

I just had a situation with wrong t-stat then a bad one right out of box.Does your fan have resistance win you spin it by hand it should not spin more than a quarter of turn. I know you said you just changed fan clutch but as I stated above new parts are not always reliable.Your heat should stay the same no matter what your doing.

 

I checked the fan and when i spin it it doesnt move to far so its good. i got the stats from a chevy dealer but thats not saying much. and it can sit for an hr at idle and the temp will go to the first line and pretty much stay there but little heat.when i give it gas the heat gets better but when i let off the throttle the heat goes down . i do have a metal upper flex hose for my upper rad hose as i added a 2nd alternator and someone said it might be that because its not smooth on the inside like the rest of the system but at this point im still at a loss

 

Dave I dont belive the metal radiator hose would have nothing to do with the symptoms you are havingdo to the fact that the water is already hot leaving the thermostat housing to the radiator you may have air trapped in the cooling system or you may have excess scaling in the radiator itself the best way I have heard to clean the radiator is by using scrubbing bubbles and flushing it with water

 

Im thinking air because for the most part the entire cooling system with the exception of the heater core is new including the rad ill let it run without the cap for a bit and see if it burps it out

 

Does it not have bleeder close to t-valve.

 

yes it does right on the top of the t-stat housing