Bubbles in coolant bottle BMW z4 e89

[AnotherZ4Owner]

I've had zero issues with this car for 7 years... Until now.

A few week ago I was driving along and my z goes into limp mode with an overheating issue. I pull over and check the coolant. It had been leaking so I topped it up. On the way home it keeps throwing the overheating light and I had to stop and pull over.

This part may be unrelated... The battery died. RACQ put a new battery in. It started, but shortly after the power would die completely when the car was turned off. Someone told me the seat modules often play up and could cause parasitic drain. Also the roof module can cause this, or an interior looking ght staying on. I pulled the fuses on all three. I put the battery on the trickle charger and charged it 3 times to fully charge it. Not the car starts fine and doesn't lose power instantly. So I'm guessing one of those modules has an issue.

However, I started the car and ran it for a few minutes. I checked the engine and there is a strange noise coming from the m the front. Could this be the water pump? If it's stuffed it would explain the overheating:

Then I took the coolant cap off (engine off) and water and bubbles are pouring out:

Now, besides a blown head gasket (which everyone has said on my past cars has been 'the issue' and which never turned out to be the issue) what could the issue be? I suspect the water pump is gone?

[Johns8403]

I would say that looks like Air in the expansion tank, if you have a leak and air is getting in you'd see some foam. When you topped it off what did you use? some colors aren't mixable with the BMW Blue.

If you have a leak air is getting in the system, which would cause you to overheat.

You'll need to fix the leak and then bleed the system using the electric waterpump. IF the electric waterpump isn't working you wouldn't be getting the stream on your picture, also you'd havea CEL.

I'd get it flushed once you've fixed it or do it yourself. Good Luck

[Our03z4]

Originally Posted by Johns8403

I would say that looks like Air in the expansion tank, if you have a leak and air is getting in you'd see some foam. When you topped it off what did you use? some colors aren't mixable with the BMW Blue.

If you have a leak air is getting in the system, which would cause you to overheat.

You'll need to fix the leak and then bleed the system using the electric waterpump. IF the electric waterpump isn't working you wouldn't be getting the stream on your picture, also you'd havea CEL.

I'd get it flushed once you've fixed it or do it yourself. Good Luck

Could be that or a blown head gasket. That coolant went some where, either out or in. You could drain the oil and seem if coolant is in the oil or go to Harbor Freight and get their exhaust gas detection kit, uses color changing liquid in a tool to see if gas is detected.

I wouldn't drive the car again until you're sure, driving over heated can and will warp the head and cause a gasket leak and worse.

[Our03z4]

I'll add that noise sounds like a diaphragm of some sort having pressure issues. There again could be combustion gas getting into the cooling system causing pressure.

[cbpip]

Have a test done for gases in the radiator. Will be able to tell immediately if you have a blown head gasket.

https://www.amazon.com/Block-Tester-.../dp/B06VVBSFTF