Re: E420 MB defective cabin heating system causing overheating

On Mar 26, 8:52 am, Derf-E420-94 <der...@xxxxxxxxx> wrote:
Would a defective cabin heating system causing engine overheating?

AFAIK, only way that could happen would be if the defect was a leak
that resulted in a loss of coolant.



When you turn on cabin heating doesn't hot coolant circulate into
cabin heating system?

Yes, but it's only flowing when the air needs to be heated. In
summer, for example, it's off and the car doesn't overheat because the
heat gets dispersed by the radiator.



When cabin heater is turned off, what closes circulation, a mechanical
or electrical valve? If stuck or won't fully close could cause
overheating?

If it was stuck, you could have a cold cabin or a ver hot cabin. But
you would not have the engine overheating.



Changed coolant fluid recently but how do you bleed coolant in heating
system?

Perhaps someone else can help you out on that specific model. In
general for almost all cars, setting cabin system to max heat and
just driving will vent the air.



Of course I checked: rad cap, hoses (external), belt, thermostat,
fluid, fans, radiator, water pump.... car heats up after 20 minutes...

How did you check the thermostat? Either the thermostat or a blocked
radiator would be the suspects. Also, though less common, could be
a radiator hose that collapses when the engine is running.




Thanks,
Derf

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