Hi ,i have a hitachi ex 455 that i overhauled the engine on isuzu 6rb1 and it is building pressure in the radiator and running hot after 30 min running ,it has a new thermostat , i suspect a blocked radiator which was probably the cause of it doing in a piston originally,took machine in this condition so i dont know previous history ,any of you guys come accross this problem before,thanks 30.331
Something to look at is....The thermostat housing is aluminum and electrolysis can erode the bottom seat for the thermostat and the coolant will bypass the radiator. Seen this many times. Pull the thermostat and look into the housing, there should be a machined flat surface. The thermostat on this model not only opens up but will seat on the bottom when it opens up to force the coolant through the rad. Or blocked radiator.
My guess would be an issue with the head gasket not sealing, have you tried re-torquing the head bolts? Leave the cap off the radiator fill it very full and see if you're getting bubbles which would indicate combustion chamber gasses leaking into the coolant. Also, was the water pump checked or replaced during overhaul? Cheers.
Thanks guys for your replies, kenAL i will inspect the thermostat housing when i get to the machine,lantraxco i dont have any bubbles or foaming showing and i didnt re-torque the head bolts,i will check out that thermostat first and take it from there ,30.331
ex200lc running hot need help
More information please. First guess is the radiator is plugged, take the oil cooler off and hose out the radiator. There's no way to tell how much junk is between the two unless you use a light on one side and can see CLEAN through from the other side, then you can only tell that it's not COMPLETELY blocked. The temperature at the inlet and outlet of the radiator is very helpful also. Or the thermostat housing, water pump inlet, same thing. Loose fan belt? Is it using any coolant?