Heater cold at idle

[sixpack]

95 C250 non turbo diesel, the heater goes cold after about 30 secs at idle. heater works normally at all other times & engine does not overheat. Theres no bubbles in the header tank, which is about half full. Temp. guage reads low at about 80, but it has always did this, no change. Its a bit annoying as the heater starts to blow cold after 30 secs at traffic lights. taking the revs up to about 1100 gives heat in about 25/20 secs. Any ideas ?

Peter

 

[spiritwolf]

Hi
Not a complete expert with mercs, but have experienced this on other cars. I would say its a partially blocked heater matrix. Lack of force from the water pump at idle is causing the water to not flow into the matrix effectively. Try buying some rad flush from halfords and half drain your system. Pour rad flush into your system. Fill back up to normal level and run for 24 hours (flush says 20 mins, but a day will do no harm) Check your system for leaks in the 24 hours. a blocked one normally means some rust in system and there may be weaknesses around in matrix. Then totally drain the system again, flush with a hosepipe and fill as normal. fingers crossed!

 

[stwat]

Sounds like air in the system to me. Try bleeding it and see if it gets any better.

stu