Replaced thermostat today, everything is working fine.... Or is it?

[Rmachines]

I replaced the thermostat after noticing it was stuck open all the time and the engine never got warm (replaced ECT prior to this)

So today i changed the thermostat, filled her up with new coolant, bled it through,  then got board and went for a short drive,  temp now stays at 90c as expected.  (85-87c on vagcom) So thats spot on.

I did 15 miles, through town, got fuel, down the dualer and home again.  I checked the radiator, its red hot at the top, but the bottom pipe and bottom of rad is cold.   No steam,  and no pressure in the system (released the cap and let off a small hiss, otherwise fine, no bubbling over)

Cabin heater blows hot.... Is this normal? 

[Wayne]

Does not sound right 

[Rmachines]

Took it out again,  went through MaccyD drive through, pulled up and felt the bottom pipe, it was warm/getting hot,  top was very hot.   Drove 2 miles up the road, and it was freezing cold.   Gauge still showing 90c,  Not boiling over,  not pressurising.

I dont get it 

[Wayne]

Could be an air lock.

[thai-wronghorse]

Id say so, might be worth running the engine for a whilst parked up with the expansion tank cap off to help expel any air bubbles in the system, maybe even leave it off completely with the engine turned off over night. Ive read that this can cure issues like this as it allows the airlock to rise out slowly.

[polo6n222]

my bottom pipe only gets hot just before the fan comes on

[tweed]

Sounds air to me. And try taking your radiator off and putting a garden hose on to see if there is any blockage

[Rmachines]

It seems to be fine now,  the bottom pipe only gets warm, not hot, but have done 200 of miles now without any issues. I did get a bubble out of the tank though so was possible air in the system