S210 Residual heat

welland99

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The other day in the freezing fog I stopped to go in a shop. I had already driven 15 miles and everything was nicely up to normal temperature (80C on the temp guage). So I decided to switch on the residual heat system to keep it toasty while in the shop.

When I pressed the button, it started blowing warm air and all seemed well.....so off I went into the shop.

20 minutes or so later, I got back in the car and discovered it was blowing quite cool. When I started the engine, I noted that the temperature guage had dropped to about 60C, but within 5 seconds I was feeling much warmer air being blown through the vents.

So, I am wondering if the residual heat system is faulty, or was the weather just too cold to cope?

My understanding is that the system pumps hot water from the engine into the heater matrix when the engine is off. Yet my engine was clearly hotter than the heater matrix when I returned to the car.

Anybody know exactly how it works?
 

bob6600

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Not sure how it works but mine seems to work as poorly as yours
 

Dec

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If your car battery was not so good then the electric water pump might only be on for maybe 10 minutes.

You would really need to stick a thermometer in the air vent and sit in the car to see just how long the residual heating will actually run for and how fast the temperatures decline.


Dec
 

whitenemesis

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Does the REST function continue to operate once one locks the car?

Not sure I like to use it anyway, as the a/c doesn't run so one is pumping humid air into the car.
 

Dec

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I only ever tried it once, with the car locked, but it is intended to work if you are just sitting in the car with engine off or if the car is locked up.

It just runs the heater blower fan on one speed only and an electric water pump to circulate the coolant around the heater/engine block, the engine thermostat will close when the temperature drops below about 80c.

I believe it won’t work if the coolant is too cold or the car battery is not healthy.
The A/C wont run while the engine is off.

Dec
 

renault12ts

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I only ever tried it once, with the car locked, but it is intended to work if you are just sitting in the car with engine off or if the car is locked up.

It just runs the heater blower fan on one speed only and an electric water pump to circulate the coolant around the heater/engine block, the engine thermostat will close when the temperature drops below about 80c.

I believe it won’t work if the coolant is too cold or the car battery is not healthy.
The A/C wont run while the engine is off.

Dec

I didn't know there was an electric pump in the system?
 

bob6600

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Maybe the pre-heater that never works?
 

W210Virgin

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renault12ts said:
I didn't know there was an electric pump in the system?

Yes a small pump sits on the o/s chassis leg just below the reservoir. I think mine is seized and I suspect that is the main issue with most of the systems thro' lack of use.
 

renault12ts

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Yes a small pump sits on the o/s chassis leg just below the reservoir. I think mine is seized and I suspect that is the main issue with most of the systems thro' lack of use.

Under the coolant reservoir? Isn't that the block heater, which operates when the engine is on at temps below 7oC...when switched on using the switch in the ash tray.
 

W210Virgin

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Yes, but a bit further down and closer to the front. Just follow the pipes and you'll see it.


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230K

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I think the electric coolant pump is supposed to run constantly when the vehicle is running.

The wife's 124 heater used to go cold when the engine was idling and a strip down and reassemble of the little electric pump gave heat heat whilst idling in traffic.

230k
 

renault12ts

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I think the electric coolant pump is supposed to run constantly when the vehicle is running.

The wife's 124 heater used to go cold when the engine was idling and a strip down and reassemble of the little electric pump gave heat heat whilst idling in traffic.

230k

Is she still driving it...recently I've only seen her in the 210?
 

W210Virgin

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Don't think that is the case in the 210 but can't say for sure. My heating is fine. Just the REST function runs out of heat suggesting the pump doesn't circulate. I'm going to do a coolant change and will check it out then.


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Lenny63

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would the CLK w208 have the same electric pump?

I honestly thought it was a case off the residual engine heat is the main source of the heat (Mine is a v8 to be fair so will be much hotter than a diesel)
 
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welland99

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W210 E280 estate 1999 facelift; 6th gen honda accord coupe 2000
Thanks for all of your posts. I tried it again yesterday and the same happened. It was blowing warm when I left the car, but when I returned, it was cold. Then, within 5 second of starting the engine, it begn to blow warm again.

This tells me that the hot water in the engine is not reaching the heater matrix when the engine is off, but it is when the engine is on.

I must have a look for the electric pump - somewhere close to the the coolant bottle? I wonder if it is possible to remove the pump without draining the coolant (eg if the motor separates from the impeller)?
 
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welland99

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It would be better to see how long it will run for first before you take the pump apart.
You will be able to feel and hear it running.
Great, thanks a lot. I will certainly assess the pump before dismantling anything. I probably won't get chance to look before the weekend, though.

Interesting feature of the E300 to circulate hot water in the washer bottle. Haven't seen that before. But I imagine that water circuit to come from the main water pump - otherwise it would only work when residual heat is being used.
 

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