Heater blows cold when idling

[manimal]

Hi

2 weeks ago i had a new radiator fitted,my blowers worked fine, last night my heater stopped blowing hot air when it was idling and only tepid air when travelling.I tried letting it overheat with the cap off to remove any air. this worked for about 30 mins then it went back to the problem again.If i rev the engine it warms up then goes cold when i stop revving.What the hell is going on ??

[Ste]

Sounds like thermostat fail to me - ie jacked open.

[manimal]

Is there a way by feeling the pipes to pinpoint the problem ?

[Vetox]

Take your thermostat off and stick it in a pan of boiling water to see if it opens or shuts.

Will let you know if the thermostat is faulty.

[manimal]

ok thanx

[Ben50n]

Does the temperature gauge come up to its normal position within 4-6 miles and stay at that temperature?

[FLOB]

let the car idle and as soon as the needle moves feel the 2 big pipes that go to the stat and if both are warming at the same rate the stat is royally ragged and locked leaving loop open.

[manimal]

Yes the gauge comes up as normal and stays there. I've noticed tonight that all of my pipes are very hot except for the left hand one coming from the matrix which is considerably cooler than the right hand one. Hope this helps.

[beat275]

Sounds like a blocked matrix to me. Had this problem on my corsa. Got I changed and worked a treat. You could also flush the system out or take the matrix out and flush that. Its a messy job though

[Ben50n]

Could just be an airlock? Or I hate to say, if the water pump is starting to fail? Try back flushing the matrix first.