Hey everyone!

Just finished doing a major service on my Polo and think I may have filled the cooling system incorrectly as I think I've identified two air locks... I thought I filled it slowly but not slowly enough!

Although, if this is all I did wrong on the service (cam belt, water pump, aux belt, thermostat, fan temperature sensor and coolant temperature sensor) then I think I'm happy as it's the first time I've ever done anything this major, but wondering if anyone can provide any tips on clearing them?

1. The heater now doesn't blow hot. The two hoses going into the heater bit (under the wind shield) are hot at the bottom (engine end) but feel cold/empty at the top (wind screen end).

2. The top radiator hose is getting warm to the level I'd expect, but the bottom radiator hose doesn't heat up at all. The top of the hose feels as though it's got liquid in it that just remains cold but the bottom of the hose (connected to the radiator) feels completely empty as if it's just got air in it. I guess this is some kind of air lock stopping the coolant from circulating rather than just the thermostat not opening but not 100% on that?

Can anyone provide any tips on getting these sorted?

Thanks in advance!

Take the cap off the expansion bottle (only with a cold engine!) then run the engine at 2~2500rpm for 15 mins as at idle the water pump isn't very effective, this should "burp out" any air locks, keep an eye on the water level and top up with water/antifreeze mix as required, then refit expansion bottle cap and again run @ same rpm for 5~10 mins then allow to cool and top up if required

Take the cap off the expansion bottle (only with a cold engine!) then run the engine at 2~2500rpm for 15 mins as at idle the water pump isn't very effective, this should "burp out" any air locks, keep an eye on the water level and top up with water/antifreeze mix as required, then refit expansion bottle cap and again run @ same rpm for 5~10 mins then allow to cool and top up if required

Perfect, thanks Nige, I'll give that a go tomorrow evening and report back.

Is there any trick to get it running at 2-2500rpm using VCDS or otherwise, or do I need to sit there with my foot on the accelerator?

No VCDS trick available as far as I know, I used a bit of rigid plastic tube onto the pedal and clamped it to the steering wheel

The bottom hose won't get hot until the thermostat opens, which actually takes quite a while at idle.