High temp alarm after coolant refill

VAG fool

VAG fool

Member
Following replacement of seals on AUA coolant pipe and repair to thermostat housing, got it all reassembled and refilled with the saved coolant.
Let the engine idle for a few minutes to warm up a little, a bit of throttle blipping and set the climate controls to 27°C.
Fan spun up a few times while I was checking for leaks (none so far!)
Nothing but cold air for a while, then finally the hot came through, followed closely by a high temp alarm.
Is this usual?
It occurred to me afterwards that maybe I should have disconnected the small bleed hose from the goldfish bowl to help it purge any air from the system?
 
VAG fool said:
Following replacement of seals on AUA coolant pipe and repair to thermostat housing, got it all reassembled and refilled with the saved coolant.
Let the engine idle for a few minutes to warm up a little, a bit of throttle blipping and set the climate controls to 27°C.
Fan spun up a few times while I was checking for leaks (none so far!)
Nothing but cold air for a while, then finally the hot came through, followed closely by a high temp alarm.
Is this usual?
It occurred to me afterwards that maybe I should have disconnected the small bleed hose from the goldfish bowl to help it purge any air from the system?
Click to expand...

I’ve just done the cambelt and water pump on my aua.
When I ran it up to temp I kept the engine on a fast idle, like you had the heater on full heat and allowed the temp to rise until it reached normal operating range, but which time there was heat coming out of the vents.

Once the car reached operating temp I let it idle at normal revs for another few mins, then I switched it off and let it cool down before removing the cap on the expansion bottle.

Whist the car was heating up I kept checking the hoses to make sure there weren’t any hot/cold spots, this would normally indicate an air lock


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Sounds like you have an air lock.
Undo the small nut under the coolant bottle and lift off the two rubber mounts. With the sensor disconnected but hoses still on, lift the bottle as high as you can without over stretching on the hoses. Run the engine with the coolant cap off and slowly add coolant mix as required as the trapped air burps up.
One other possible cause is you put the thermostat in the wrong way around.
 
I'll try that, I think its an air lock. Its got a conventional type thermostat, not the little capsule one. Its impossible to fit the wrong way round.
IMG_20210513_182113_3_resize_97.jpg
 
Heater temperature selection makes no difference to the water flow through the cabin heater. Have you opened any bleed screws up? Not doubting your repair but can fluid pass through, if not that could be causing the air lock. Did you run the car up to temperature with the cap off the expansion tank ( goldfish bowl )?

Three times I have seen the thermostat fitted the wrong way round...
 
There are bleed screws? I couldnt find any! The repaired spigot hose is returning coolant to the tank so I think all is ok now.
I am still puzzled by the OEM 83°C stat dated 03 02...

PS the level had dropped a little as it cooled down overnight so I topped it up while running.

I forgot that these are full-flow heaters, I'm stuck in the 80's ;)
 
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