problem with heater w210

amkahal

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Hi, i am new to the forum.

my heater is not working, air blowing is ok but not heat on E230 1997 M111, the recirculating pump is running but when i unplug the hose (from pump to duo valve) there is no water flow at all, so can the pump be faulty ?

sorry for my bad english.
 

Steve@Avantgarde

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I would suspect the engine thermostat has jammed shut preventing circulation. Run the engine for 20 mins and check the temp of the top and bottom coolant hoses, both should be hot to touch. If the bottom hose is cold or only warm then that is your fault.
 
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amkahal

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i will check and then tell you.

but i have noticed that the engine temperature is below 80c (at 50~60c) after driving 20 miles or more, is it a sign of thermostat failure ??
 

Dec

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i will check and then tell you.

but i have noticed that the engine temperature is below 80c (at 50~60c) after driving 20 miles or more, is it a sign of thermostat failure ??

And yes again.

Dec
 
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amkahal

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but when i stop with the car for a 5 minutes while the engine is running, the temp reach ~80c, should the heater works in this case, even if the thermostat fails ??
 

television

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The engine does need to be at 85 or better to get any heat, you can check the duo valve by feel, when it is working on both sides you can touch each output pipe and you can feel the pulse working, about 5 pulses per second when set to max
 

whitenemesis

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but when i stop with the car for a 5 minutes while the engine is running, the temp reach ~80c, should the heater works in this case, even if the thermostat fails ??

Of course it will, there is no air flowing through the radiator to cool it down. If the thermostat is working correctly it will prevent the water flowing through the radiator when you are moving.
 

spock500

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Check the water pump too as some of these are prone to failure.

Maybe not same engine/pump but possibly similar.

461709d1344796038-e300td-1998-coolant-boils-fo-no-france-summer-2006-154-medium-small
 

mersum1es

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There is a separate circulation pump (a31m1) which helps water to the heater matrix. It's not needed but helps cabin warm up if the engine is not yet fully heated. It's next to due valves in some models, in W210 should be next to the expansion tank...
 

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Of course it will, there is no air flowing through the radiator to cool it down. If the thermostat is working correctly it will prevent the water flowing through the radiator when you are moving.

Cars do have fans that cut in to cool via the rad and maintain a constant temp.
In some cases the rad can get blocked in front of the hot spot that prevents visco fans from cutting in
 

whitenemesis

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Cars do have fans that cut in to cool via the rad and maintain a constant temp.
In some cases the rad can get blocked in front of the hot spot that prevents visco fans from cutting in

Certainly not the issue here. :rolleyes: The coolant is never going to get hot enough to trigger the fan!
 

television

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Certainly not the issue here. :rolleyes: The coolant is never going to get hot enough to trigger the fan!

I was only adding this info :D, and sure enough the thermostat is passed its best in this case, when the thermostat has been changed the OP needs to check that the visco cuts in at about 3 degrees over the thermostat opening temp, usually about 87c
 
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amkahal

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OK, yesterday i have changed the thermostat to a new one with 71C, i didn't find higher than this temperature, but still no hot air.

the question is, how to diagnostic if my problem is from the duo valve without disassembling it ? is there any chance that the heater radiator is blocked ??
 
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television

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There is not a 71c thermostat made ???, the heater matrix could be blocked and this can happen.

If the rad fan kicks in to full power once the thermostat has opened, the main rad is OK as the hot air passing through the rad triggers the bi metal strip in the visco cooling fan.

With the heater controls set to max heat, if the duo valve is OK then you can feel the pulses on the 2 outlet pipes that go to the car heater matrix, about 3 per second, and the pipe should feel hot.
 
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amkahal

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it's typed on the thermostat: 71C.
just to note that the circulating pump is running when the engine on and off.
 

mersum1es

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And unplugging the wires of duo valves should also produce hot air (exclude heater control failure).
 
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amkahal

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i tried to unplug the duo valve connection with no success, i will try to inspect the pulses of duo valve today.
 

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What tempature was typed on the old origional thermostat?

Dec
 

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