Overheating 2 days after coolant change/flush

[Matt21]

As the title says, I changed coolant and expansion bottle on my mk3 150 bhp tdi, all running fine since doing it until today, temp will reach 90°c and stay there for a little while until the oil temp reaches roughly 100°c, then coolant temp will starts to rise in the dashboard sensor, hot air still coming into cabin, no loss of coolant so levels are fine, could thermostat be knackered or water pump or something totally different? If so then luck really isn’t on my side


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[BigJase88]

Sounds like an air lock?

Did you run the car upto temp with the coolant reservoir cap left off so it could bleed

 

[Matt21]

Sounds like an air lock?

Did you run the car upto temp with the coolant reservoir cap left off so it could bleed

I did yeah, I’ll try it again tomorrow after work to make sure again, I ran it with cap off and heater on, you can see it returning back to the tank through the return line, turn heater off and the expansion tank overflows which made me think either thermostat or water pump


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[Big Col]

my understanding is the coolant change/bleed on these is far from straight forward.

There's more than one cooling circuit and you need to operate valves, vacuums and pumps to bleed it properly.
One of the settings in vcds is bleeding of the coolant circuits.

 

[Matt21]

my understanding is the coolant change/bleed on these is far from straight forward.

There's more than one cooling circuit and you need to operate valves, vacuums and pumps to bleed it properly.
One of the settings in vcds is bleeding of the coolant circuits.

I do have a dongle from albionshire diagnostics with the bleeding the cooling circuits, I'll give them an email and see how to operate it

 

[Matt21]

Pretty sure water pump has failed, plugging in my dongle and activating the switchable water pump, there is zero flow what so ever from the return line, cold or warmed up there’s zero flow


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