Cab heater will not run cool when idling, but is OK when at speed.
WDB903 sprinter 1999, 4 tonne flatback. Radiator heat is ok, no overheating at all, but the cab heater will not deliver cool air when idling in traffic. As soon as one gains speed, the outlet gradually becomes cool again. Is this vacuum related?
Re: Cab heater will not run cool when idling, but is OK...
Some cars have a vacume check valve on the vacume line that
activates the air duct to open and close . If the vacume is not right
it will not work properly . If the vacume check valve is ok then check
and make sure the heater core is not clogged up
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1) Coolant tank may show full but radiator is low in coolant...Cold engine...remove cap...inspect coolant level in radiator...fill if necessary,,,
2) If #1 is OK, the coolant system has an air blockage...With cold engine remove cap...Start engine...Heat control on high... when thermostat opens coolant AND air will escape from radiator...there will be coolant loss...Wait until all air escapes then carefully replace cap...When engine cools remove cap and top off coolant if required.....saailer
Does the radiator fan come on before it overheats? And is it boiling over, or just showing hot on the gauge ? Is the cooling system full of coolant and no air pockets ? How do you know the thermostat is ok ?
Check first your coolant level. Start engine and turn on ac open hood see if cooling fans are running, if fans are running and coolant level is ok temperature should stay normal. If temperature rises squeeze coolant hose, it should be firm like you could feel pressure on the hose a sign that the water pump is good. Thermostat opens only when coolant reach normal operating temperature.
disconnect the heat hoses going into fire wall , put hose into one with pressure and flush as it sounds like it could be bloked in the heater core,the other thing that could be the problem be the hot ,cold switch as it restricts the flow to makes the heater hoter or colder , it might need tlc or replacing as it is manaul not elec
Sounds like you have a problem with the cooling system. First thing you need to check first if the auxillary fans are working from the time you are the engine is overheating. If the auxillary fans is not working then the problem would be the aux fan itself or relays. if Fan is working then you might have a poblem with the water pump.
No,this is not normal,make sure there is enough coolant in the radiator,and reservoir ,if there is,make sure there is no air in the cooling system,if there is,bleed it out,if all this checks out ok,flush the heater core out with a water hose
I am assuming your vehicle has the pink antifreeze called Dexcool. This is the recommended coolant for all late model GM cars and trucks. This coolant tends to form a pasty sludge in the cooling system which can lead to overheating and/or plugged up heater core. Try flushing the cooling system with a good aftermarket product such as prestone radiator flush. First thing to do is drain all the pink coolant, then add the radiator flush and fill with plain water. Run the engine according to directions on the flush container. Drain the radiator again and refill with plain water. Run the engine for a few minutes and drain again. Keep repeating this until all the pink antifreeze has been eliminated. Fill the system with 2 gallons of green antifreeze. Make sure the antifreeze container says it is compatible with aluminum engine parts. Hope this helps. If it does, then you won't have to replace the heater core.
could also be that the water level in the radiator is too low. if water is ok then it could well be as yo ustated, that the thermostat is stuck in the closed position. thus over heating the engine and not letting the hot water out into the cooling and cab heating system. to test thermostat remove when engine is cold and put in a glass of boiling water and watch to see if it openes. also try to run you car with the thermostat removed close the housing back up with a gasket fitted. and see if this resolves the problem you may have to choke the car a bit longer as it will take longer to warm up but it should be ok just for a test.
Warning: water cooling systems are under pressure when breaching a system ensure precausing are made not to get burned release the opening valve slowly with a rag over the valve to allow the pressure to release in a controlled way.
When driving down highway only, it overheats? When running steady, I take it you mean, sitting idling? If it's only overheating at highway speeds, and all else has been checked out & is o.k., I'd take a close look at rad hoses for soft spots (easy to squeeze) that may be causing hoses to collapse at highway speeds & restricting flow of cooling system. Another thing to try is, turn your heater on high fan & high temperature when it starts to heat up & see if temperature gauge goes down (cooler) at all. If it does, then rad not doing it's job properly.
No water pump issues I am aware off, are you sure you bled the air out of the cooling system? If not fill the overflow bottle all the way full, then use a floor jack and raise the front of the car as high as you can ( this allows air to go to top of radiator tank), then run the engine at high idle speed until the cooling fan ( I assume the fan works OK?) comes on, but avoid letting the engine get into the overheat area of the guage, if it does turn it off, run water over the radiator until it cools, check the tank and radiator, top off if you need to and repeat above procedure, if this doesn't work you have some other problem like no or little flow in radiator.
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