Audi s1 coolant bubbling

[Danyceest]

Hi guys I have recently brought a audi s1 2016 72k and noticed my coolant was low when getting home i topped it up and kept my eye on it but noticed their was quite alot of turbulence in the reservoir when the car was running and wasn't sure if it was normal or not so I had a mechanic come out and check he said it was normal flow from the waterpump return. A few days later I noticed a small steady stream of tiny bubbles coming across the seam of the tank so I waited for the car to cool down but still quite hot and took of the cap to inspect the flow their was a nice hiss and the coolant risen up the tank and i got a friend to rev the engine and their was alot of bubbles and what looks to be froth from the return hose on acceleration the car was up to temp I don't seem to be losing any coolant the heaters blow boiling hot and consistent throughout the vents I've changed the coolant cap for a belstine one and used a chemical leak test wich stayed blue is this possible head gasket or possible air in the system or just turbulence i also might of made a mistake of draining the header tank and squeezing the return hose could of possibly introduced air (engine of) Thanks here Is a video when accelerating

https://youtube.com/shorts/YgzTFhoUJVI?si=o-eB-erB...

[Danyceest]

Just to add i didn't notice the bubbles in coolant untill I drained the header tank with a baster and thought it was a good idea to squeeze the top hoses wich did bubble but was partially empty wich looking back now was silly todo as I didn't notice actuall bubbles untill a few days after this.

[Krikkit]

Danyceest said:

Hi guys I have recently brought a audi s1 2016 72k and noticed my coolant was low when getting home i topped it up and kept my eye on it but noticed their was quite alot of turbulence in the reservoir when the car was running and wasn't sure if it was normal or not so I had a mechanic come out and check he said it was normal flow from the waterpump return.

That sounds completely normal.

Danyceest said:

A few days later I noticed a small steady stream of tiny bubbles coming across the seam of the tank...

So the tank is leaking? Get a new one fitted, a very easy and cheap job.

Danyceest said:

...so I waited for the car to cool down but still quite hot and took of the cap to inspect the flow their was a nice hiss and the coolant risen up the tank and i got a friend to rev the engine and their was alot of bubbles and what looks to be froth from the return hose on acceleration the car was up to temp I don't seem to be losing any coolant the heaters blow boiling hot and consistent throughout the vents

So it's perfectly fine.

Danyceest said:

I've changed the coolant cap for a belstine one

You mean a Febi Bilstein one?

Danyceest said:

...and used a chemical leak test wich stayed blue

So what did the instructions with the test say it should do?

Danyceest said:

https://youtube.com/shorts/YgzTFhoUJVI?si=o-eB-erB...

This is completely normal.

[Rowe]

Sounds like you need to stop worrying about it if it's clear on a hydrocarbon test and its not losing coolant.

[Danyceest]

Thanks for your reply yes it was a febi one as no dealers had one around and no it wasn't outside of the tank it was inside the tank like a stream of bubbles around the surface of the coolant I have uploaded another video with cap on https://youtu.be/e9yqdKoDR9g?si=vkJexrmJEkUsr9io sorry for shakey cam I didn't notice any bubbles only the turbulence so I drained the tank to look at the coolant colour and while it was low I gave the hoses a squeeze could this of brought the air in ? Or is it just turbulence. Thanks