Cabin heat not as hot as should be themostat top hose from radiator hot bottom cool

[Smith007]

2002 ML320 24000.00 km
Interior or cabin heat low
Cabin heat not as hot as should discovered that the large top hose from radiator to thermostat and engine is hotand bottom radiator hose is cool to the touch even though the dash temperature reads plus 80

Is this the themostat not opening and therefore low and not hot interior or cabin heat?

[mbdoc]

The only coolant temp that needs to be hot is the top hose & the heater supply hose.

On that truck, there isn't a heater valve & coolant is always flowing thru the heater core.

To see if the blend air system is working, you need to remove the glove box liner & with the ML running move the temp dial back & forth & then watch the blend air flap move.

[Smith007]

Once again Doc thanks for responding so quickly - the blend air actuator is oscilating from hot to cold

PS However, Doc on second thoughts let me look at the air flap again - thus a question which hose or where is the heater supply hose??

[Smith007]

PS However, Doc on second thoughts let me look at the air flap again - as it was some time ago Thus a question which hose or where is the heater supply hose??

Would the Coolant Circulation Pump also come into play??

[mbdoc]

Yes, the aux coolant pump should be running any time the truck is running. IT pulls coolant thru the heater core.

Should run up to 10 minutes after shutting off the engine as well

[JamesDean]

Originally Posted by mbdoc

Yes, the aux coolant pump should be running any time the truck is running. IT pulls coolant thru the heater core.

Should run up to 10 minutes after shutting off the engine as well

Not to thread jack, but is this the case in the 201 as well? I've had my aux pump uplugged for a while now and have noticed no difference in heat temps.

Now in my 124, I think the aux pump has failed and I get very poor heat at low speeds.

[mbdoc]

James, The ML & some of the W140 chassis cars do that..not on a W124 or 201 chassis.