Temp help

[Jay Kilby]

Hi i have a 1981 500sl which i have collected on the way home we started having fun with the engine temp. it started to get really high then if i moved the heater to hot the engine temp went down.
now i think it is a faulty thermostat not opening when it should, because after a while the temp dropped below 80deg with the internal heater on cold then for no reason the engine temp went up again??

any tips would be good

thank you

 

[television]

I know this is a basic question was there enough water in the system.

Malcolm

 

[Jay Kilby]

yes i checked it last night it gets up to the red before the thermostat opens, then drops right down to normal, then the thermostat closes and it heats up again.
just wanted some comformation

 

[television]

yes i checked it last night it gets up to the red before the thermostat opens, then drops right down to normal, then the thermostat closes and it heats up again.
just wanted some comformation

the thermostat has to be faulty (out of range) there is nothing else that can do this.

Malcolm

 

[Jay Kilby]

O.k. i am at a loss here. my car when started from cold was heating right up to the red, then would go down to normal temp range of 80deg. so i have replaced the thermostat with a MB version (Opens at 77Deg) while i was about it totally drained the coolant from the block. re-filled brought up to temp all lovely no problem.
the next time i drove the car same thing happened temp goes right up to 120Deg but never loads the header system enough that steam starts comming out of the overflow! it always drops down to normal but in this weather i really do not want to pop a head gasket. any idears people?

thanks