Weird Heater Problem?

[GeoffBW]

Having a problem with my '96 C250D. The blower will not blow hot whilst the engine is idling. When moving the heater works normally but as soon as I stop, the air very quickly turns cold - even if I'm just stood at traffic lights for a couple of minutes. Have also tried running downhill in neutral at 50 mph but the air still goes cold whilst the engine is not working. Engine temp. guage stays steady at 82 deg.
No previous water problems over 12 mths. I've had the car but unexpectedly had a warning light a couple of weeks ago to say the expansion tank was empty so I filled it up and the level has stayed constant since (!000 miles+).
Can anyone help?
Many thanks
Geoff

 

[television]

Do check 150 in the link,,its the re circulating pump

http://www.detali.ru/cat/oem_mb2.as...GM=717.417&CT=F&cat=44V&SID=83&SGR=180&SGN=05

Welcome to the forum

 

[dragon]

Good Morning, Malcolm.

If the expansion tank it empty and being filled, isn't air lock that caused the problem. Need some massage of the coolant pipes.

 

[television]

Good Morning, Malcolm.

If the expansion tank it empty and being filled, isn't air lock that caused the problem. Need some massage of the coolant pipes.

And good morning to you,, these things are normally self bleeding once the water starts to circulate, one can certainly squeeze the fat bottom hose with the cap off to see if any air bubbles come to the top through the header tank

 

[dragon]

The OP said it intermittent, it will cure itself. Yes?

 

[television]

The OP said it intermittent, it will cure itself. Yes?

Everyone that I have known has bled itself once the thermostat is open

 

[GeoffBW]

Thanks both,
Am away for a couple of days but will investigate the recirc. pump and squeeze some hoses on Saturday morning.
Geoff

 

[dragon]

Turn on high heat and max fan for a couple of minutes and ensure the reservoir between marks. If it below the min mark, find out why it leaking coolant.

 

[wireman]

I'll go with Malcolm and say the little electric pump which is either alone or integrated into the duovalve body. There may be a fuse for it or it could just be jammed or worn out, its gland may be the reason for the water loss.

Make sure your antifreeze/corrosion inhibitor strength is sufficient (>30% pref 50%) or long term damage may occur to the entire cooling system.

 

[GeoffBW]

New (second hand!) pump fitted. Problem solved. Many thanks for the assistance.
Geoff

 

[anyweb]

well done to Malcolm for spotting the problem and thanks to Geoff for reporting the solution

cheers
anyweb