Heater Blowing Cold And Hot

[essychris76]

hi to you all and i hope to find some light at the end of the tunnel on this one.i own a mk2 1.9tdi galaxy wich is causing me a real head pain as its blowing cold air out the heater and if i rev it up it will go warm as if its an air lock.the car over heated on me a while back when on the motor way and when i checked the tank it was empty so i changed cam belt and water pump thinking the plastick wheel on the pump was at fault but no. so i then changed the thermostat thinking its that blocked but no its still the same.so if i go under the bonet and check my botom hose is stone cold and presurized so i find out that the only things left to check are for the dreded head gasket but the car dosent over heat at all while driving round town its only when under load on motorway with no tell tail sighns of head or gasket failure. so some one tells me they are fitted with an external water pump so what do you think could it be this external water pump or does the head have to come off cheers every one

[boffa]

Yeah, there is run on pump that has an effect on the cabin temp. If it's not working then all you get is cold air through the blowers. http://www.fordgalaxy.org.uk/ford/index.ph...mp;hl=themastat .This was my original problem last May, and if you read through it all, you'll see that it was a lot more involved and ended up in it costing a fortune. If you're handy, you can get new brushes for the pump and refurb it yourself but Fords charged me