Hi,

My 1.5 TSI DADA engine is overheating - after driving a short distance, the needle moves to 130 degrees and the fan starts spinning very quickly. After a while, at this level, the needle quickly returns to 90 degrees, the fan slows down and you can drive another section (about 1 km). The fluid level is correct.

Where and how to look for the cause? Is there a procedure, e.g. in CarScanner, for testing/filling/bleeding the cooling system?

I would be grateful for any advice and tips

Googled and known issues with waterpump or thermostat housing leaks but if the level is correct, it doesn’t sound like you’re losing water.

In which case. I’d thinking about thermostat sticking? It should open and close with the temp of the water but if it’s stuck and not opening fully then the water doesn’t get to run through the radiator sufficiently? Just a massive guess though

In the evening I did another test. I started the cold engine and checked the coolant heating up. In the meantime I removed the return hose and checked if the fluid was returning to the reservoir through it. The fluid was returning, which may mean that the pump is working properly.

The temperature reached 90 degrees and the needle stopped. I held the revs at 2000 for a while and after a while the needle went towards the red zone. I left the engine idling for a while and the needle was almost at 130 degrees. During this time the winds on the radiator were spinning very fast.

In my opinion, such symptoms suggest that for some reason the fluid is not flowing through the radiator, something is not letting it in there despite the parameters indicating that the fluid needs to be let into the radiator.

In older cars, this is controlled by a thermostat. I do not see a thermostat on the diagrams in DADA - but there is a regulator on the pump.

Can anyone advise something based on my tests/observations, how to fix this?

Thank you in advance for any tips and advice.

Learned that water pump actuator unit [05E907593] does same job as thermostat - let coolant into radiator after reaching parameters (large circle). At mine it doesn't happen so engine temp rises and fan starts spinning quicker and quicker to cool down the empty radiator.

Could the actuator break because of engine overheating? Can it be also because of air in cooling system? If so how to effectively let air out of it?

Thanks in advance for any hints and informations.

Sounds plausible - shows how old my understanding is! Good research 👍

Problem seems to be solved. Thinking the reason of overheating was an air lock in the system after coolant change. Did another bleeding on saturday and right after reaching the temperature I was pressing coolant hoses in many places many times. Right after this I felt warm on the radiator and connected hoses. Drove about 50 km (some in the city and some on a highway with 140km/h) and the indicator still shows 90 degrees. CarScanner shows 95 - 101 degrees on both gauges (max 105 within a while of waiting on traffic lights).

Thanks all for your hints and advices.

Ok. I have the same problem on the same engine. How did you bleeding the system?! What you mean? With diagnostic tool or did you remove again the coolant and refill again?!