No heat at idle
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C350
No heat at idle
Hey Guys,
I have a C350 with 40k and I have noticed that when I come to a stop light the heat is becoming less and less hot. Once I start driving it is fine again. Does this car have a coolant circulation pump?
I have a C350 with 40k and I have noticed that when I come to a stop light the heat is becoming less and less hot. Once I start driving it is fine again. Does this car have a coolant circulation pump?
Thread Starter
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C350
maybe someone would be nice enough to go and try this in their w204? Its 18 degrees in Chicago right now and my issue happens when I am in "drive" and stopped (600 rpm) with the temp dials on the red dot and the fan all the way up. The temp of the air blowing tapers down until it feels like just the fan is blowing, no heat.
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From: 1 hours drive north of Sydney Australia
2007 W204 220CDI Classic Sedan
Just a thought .. with the ambient temp below freezing & the engine not producing much heat at idle, it may be struggling to maintain its efficient operating temperature.
The system may be clever enough to stop you pulling heat into the cab? This may be BS.
I think the only coolant recirc pump is driven by the serpentine auxilliary belt. At idle this pump is not circulating as much coolant through the system hence not picking up much heat from the head & block, therefore another reason for the poor performance of the heater.
It will be interesting to hear from another member who lives in a cold climate. Can't help you here mate as we are having 28- 30 ' c days here !!
Is your engine running at its normal operating temp ? ie around 90'C . It not the thermostat may have failed open.
I understand that there is also an electrical pre heater which operates to warm the cab almost instantly from cold. I do not know how this affects the system.
The system may be clever enough to stop you pulling heat into the cab? This may be BS.
I think the only coolant recirc pump is driven by the serpentine auxilliary belt. At idle this pump is not circulating as much coolant through the system hence not picking up much heat from the head & block, therefore another reason for the poor performance of the heater.
It will be interesting to hear from another member who lives in a cold climate. Can't help you here mate as we are having 28- 30 ' c days here !!
Is your engine running at its normal operating temp ? ie around 90'C . It not the thermostat may have failed open.
I understand that there is also an electrical pre heater which operates to warm the cab almost instantly from cold. I do not know how this affects the system.
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C350
After some more testing, it has to just be so cold that the coolant going though the heater core gets cold. When I put it on recirculate, it starts getting hot again (since its not taking 18 degree air and trying to warm it up to 85) only down side is my windows fog up and I have to crack open a window.
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From: Delaware
2004 Mazda6, 1993 RX7
Based on last 2 posts, I'd add turning down the heater fan speed a bit (if possible on a C250), to bring up the temp.
Check:
1) rad fan should not come on at those temps
2) during a cold idle, water exiting the t-stat and hosed to the radiator, should be cold at the T-stat exit point (T-stat ~closed, all hot water from rad goes through heater coil). Hand check. ---> verify
If hot, T-stat stuck open.
3) if sustained cold weather, see if MB had partial radiator blocks.
.
Check:
1) rad fan should not come on at those temps
2) during a cold idle, water exiting the t-stat and hosed to the radiator, should be cold at the T-stat exit point (T-stat ~closed, all hot water from rad goes through heater coil). Hand check. ---> verify
If hot, T-stat stuck open.
3) if sustained cold weather, see if MB had partial radiator blocks.
.
Last edited by kevink2; Feb 20, 2013 at 03:42 PM.
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C350
I got this checked out at Loeber Mercedes in Lincolnwood this week and they are telling me it is a known design flaw. New models have a aux coolant pump to alleviate this issue. Most people don't notice it so I guess I am special. They are changing the diverter valve and doing a flush for good measure. :V crap mercedes
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From: Southwest USA
Another round of ICE
The underlying assumption of the process is incorrect. Given the large amount of oil in the pan, these engines warm up most quickly under load. She should start the car with the HVAC on AUTO, heated seat on three stripes. and drive at moderate speeds until the engine is warm. Prolonged idling is wrong for several reasons...waste of gas, pollution, and very ineffective warming of the car.
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G63
The underlying assumption of the process is incorrect. Given the large amount of oil in the pan, these engines warm up most quickly under load. She should start the car with the HVAC on AUTO, heated seat on three stripes. and drive at moderate speeds until the engine is warm. Prolonged idling is wrong for several reasons...waste of gas, pollution, and very ineffective warming of the car.
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From: Dallas
My Wife's 2002 s55; (2) 1971 240z's
Hotelcrazy maybe right. I have people complain about this same problem. The first thing to check is the coolant, if it is low or has a air pocket in the heating system it will act like that.
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From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Is your auxiliary coolant pump operating? The primary function of the Aux coolant pump is to provide heat to the cabin for a while after shut down but it would sure help in this situation at idle if the system has no air in it. Dealer might have to switch it in at idle using Star to set the ECU. Under normal conditions the engine water pump will suffice.
The other issue could be with the blender flap actuator on the HVAC that blends cold & hot air.
This is the W203 diagram but the W204 essentially operates in the same fashion.
The other issue could be with the blender flap actuator on the HVAC that blends cold & hot air.
This is the W203 diagram but the W204 essentially operates in the same fashion.
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From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Aux coolant pump.
I have been doing some searching. I have never seen a W203, W204 or W209 without an Auxiliary Coolant pump. However on checking some pictures of US cars I note that some have them omitted. Cost saving measure maybe? So much for all the Benz speak that it is not only for cabin heat but to prevent hotspots in the engine on heat soak & cool down.
If your car has no Aux coolant pump maybe you should fit one.
W204 with pump attached to surge tank below.
W204 without pump attached to surge tank below. US car.
W203/W209 with aux coolant pump etc.
Very strange!
If your car has no Aux coolant pump maybe you should fit one.
W204 with pump attached to surge tank below.
W204 without pump attached to surge tank below. US car.
W203/W209 with aux coolant pump etc.
Very strange!
Last edited by Glyn M Ruck; Feb 10, 2014 at 09:07 PM.
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G63
Thanks Glyn. I check and my 2010 has the aux pump. I went out this morning, fired the car up and put the defroster on. I let the car idle for few minutes while I cleared some ice and snow in my driveway. I jumped in and everything worked fine for me....ice was melting on the windows. So I have never been able to replicate what my wife had occur last week.
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2025 AMG E 53; 2018 GLC300 4Matic; 2003 360 Modena
I duplicated this with my 2010 W204. Pretty much as 95 described and never noticed it up until he mentioned it.
My settings are Auto, 70 DS, 72 PS. AC is not activated. Coolant level is to spec, car warms up fine. While driving, as the car warms up - there is hot air mostly via floor and side dash vents. At stoplights, the air quickly cools down. Immediately upon driving from the light the air warms back up. I'm not in recirc mode and my windows don't fog up at all.
This is only while the car warms up, though. Once the car is at full operating temperature - the cooling of the air stops happening.
I'm in Chicago area also, and this was the case this morning with -3 indicated.
My settings are Auto, 70 DS, 72 PS. AC is not activated. Coolant level is to spec, car warms up fine. While driving, as the car warms up - there is hot air mostly via floor and side dash vents. At stoplights, the air quickly cools down. Immediately upon driving from the light the air warms back up. I'm not in recirc mode and my windows don't fog up at all.
This is only while the car warms up, though. Once the car is at full operating temperature - the cooling of the air stops happening.
I'm in Chicago area also, and this was the case this morning with -3 indicated.
Last edited by kjb55; Feb 11, 2014 at 11:58 PM. Reason: spelling
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From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
I duplicated this with my 2010 W204. Pretty much as 95 described and never noticed it up until he mentioned it.
My settings are Auto, 70 DS, 72 PS. AC is not activated. Coolant level is to spec, car warms up fine. While driving, as the car warms up - there is hot air mostly via floor and side dash vents. At stoplights, the air quickly cools down. Immediately upon driving from the light the air warms back up. I'm not in recirc mode and my windows don't fog up at all.
This is only while the car warms up, though. Once the car is at full operating temperature - the cooling of the air stops happening.
I'm in Chicago area also, and this was the case this morning with -3 indicated.
My settings are Auto, 70 DS, 72 PS. AC is not activated. Coolant level is to spec, car warms up fine. While driving, as the car warms up - there is hot air mostly via floor and side dash vents. At stoplights, the air quickly cools down. Immediately upon driving from the light the air warms back up. I'm not in recirc mode and my windows don't fog up at all.
This is only while the car warms up, though. Once the car is at full operating temperature - the cooling of the air stops happening.
I'm in Chicago area also, and this was the case this morning with -3 indicated.
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G63
Glyn,
I have read that the c300 has a three-phase cooling system helps the engine warm up very quickly. When the engine is first started, no coolant circulates. Then, as the engine warms up, coolant begins to circulate within the engine, but not through the radiator. Only when the coolant temperature reaches 221 degrees Farenheit (or 189 degrees F. under high load), coolant also circulates through the radiator. Coolant circulation through the heating system for the car's interior is controlled separately.
Is this a possibility??
I have read that the c300 has a three-phase cooling system helps the engine warm up very quickly. When the engine is first started, no coolant circulates. Then, as the engine warms up, coolant begins to circulate within the engine, but not through the radiator. Only when the coolant temperature reaches 221 degrees Farenheit (or 189 degrees F. under high load), coolant also circulates through the radiator. Coolant circulation through the heating system for the car's interior is controlled separately.
Is this a possibility??
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From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
The auxilliary coolant pump takes heat from the engine block to supply the heater heat exchanger. Heating is almost instantaneous after a cold start in our SA mild climate. Guess it would take a little longer in a freezing Illinois winter.
Here is the operation of the multiphase electronic thermostat. Designed to achieve maximum efficiency out of the engine.
Here is the operation of the multiphase electronic thermostat. Designed to achieve maximum efficiency out of the engine.
Last edited by Glyn M Ruck; Feb 12, 2014 at 08:22 AM.
