After the expansion tank on my mk4 polo 1.6 decided to blow all the coolant out of the expansion bottle, i checked the top pipe on the radiator which was scorching hot and the bottom one was cold, needed the car on the road asap so dropped the thermostat out for a temp fix. i wasn't sure if the headgasket had blown at first as the car now seems to get to temp far too quickly and the hot air doesnt work on idle, before the car would take about 10 mins to get to temp now it gets upto 90 in about a minute and the fan kicks in every two minutes to stop the engine overheating. Wierd thing is that the air blows out warm-hot when the cars is revved and also the temp drops dramatically when the car goes over 20mph, could this be the waterpump as it seems to be returning water on idle? I've flushed the radiator and matrix twice and bled the cooling system but running out of ideas now, any ideas would be much appreciated, cheers Bobby

Edited 12 April, 200719 yr by lowpolo7

Think you could be right when you say "could it be the waterpump". Thats what it sounds like to me as though the water isnt circulating. Maybe someone else with a mk4 may have had same problem & can confirm the same problem & cure.

cheers mate reckon i'll try a new waterpump on it, though the car is getting heat through the heater matrix now the airlock has worked it way out, how much are the waterpumps from gsf or is better to go to vw main stealer?

Dont know where is best to get waterpumps from at the moment. Mine should have been £25 + vat from gsf + £5 timing belt + anti-freeze. Had to get mine from a local motor factors though as the engine was already in pieces. Cost £40 for just the pump.

first thing you should have checked was the seal on the cap!

well the expnsion tank seems to be holding presure ok so cap seems fine, drove to leeds to manchester and back ok , dropped the thermostat out and the temp stayed below 90 all the way there due to airflow at speed and bigger water circulation route. The water seems to be constant return to the expansion tank and rises as the revs increase so not sure if its the waterpump, should the amount of water bing returned be a trickle or constant flow. thinking maybe the one of the impellers on the pump might of broken off or are they metal/plasti?. Could a slight missfire could the overheating as th car seems to be not too smooth on idle as it used to be?! any help would be much appreciated thanks Bobby

well the expnsion tank seems to be holding presure ok so cap seems fine, drove to leeds to manchester and back ok , dropped the thermostat out and the temp stayed below 90 all the way there due to airflow at speed and bigger water circulation route. The water seems to be constant return to the expansion tank and rises as the revs increase so not sure if its the waterpump, should the amount of water bing returned be a trickle or constant flow. thinking maybe the one of the impellers on the pump might of broken off or are they metal/plasti?. Could a slight missfire could the overheating as th car seems to be not too smooth on idle as it used to be?! any help would be much appreciated thanks Bobby

i have a mate at the mo with the same problem it seems failry common this does anyone have a cure for it it seems like the thermostat is stuck but i have changed it and all seemed fine but after a few trips it started to over heat again i really cant work out what the prob is. the water pump seems to be fine i.e{water flow increases as revs do} rad is fine {flushed} i just cant find the prob

Is the fan cutting in?

Sounds to me like the thermostat is fucked and there was a bit of an air block from the draining / refilling...

The exact same thing happened to my mate.

If it won't get hot enough so the fan will cut in - get a new thermo and retry - when you know the fan works with the new thermostat - if the temp drops correctly as normal and the water is clearly flowing to set the fan off - leave it to complete the cycle and let the car cool - then top up the coolant to the correct level again.

Dave