Water Temp Fluctuation

[Guest dillon1]

hi hard to explain van runs ok then water temp gage goes right up then down to nothing and van makes knocking noise no warning lights on sometimes the temp gage comes back up to normal and knocking stops when van is stopped and started again temp gage normal very frustrating help any ideas thanx ;) :angry:

[techbod]

check the wiring to the coolant temp sensor see if they are shorting out or plug connection pins need cleaning you will find it where the thermostat housing is