Except the system doesn't run at 30 psi except for during an overheat condition, which really doesn't matter anyway since the engine should be shut off. The 2bar could work, if BMW didn't make shit quality expansion tanks and hoses. The expansion tank on my E30 is 25 years old and rock solid. You never hear about people replacing them unless they want a clean looking white one.

More opinions. "Bmw makes shitty quality hoses and expansion tanks". I beg to differ and at the same time ask what your definition of shitty is? I have a 15 year old cooling system on one of my DDs with over 130k and it's still rockin so I have a different opinion. Maybe this is a fluke idk. I have read similar experiences.

Not an opinion. Do some searching here first. Expansion tanks must be how BMW makes most of their money. It is also not an opinion that my 4.8is has never had an issue with the 1.4 bar cap. Yes, my tank blew up too, maybe because I overfilled it, I don't know, it was 2 years old. I replaced hoses and tank, and 1.4 bar cap. No issue since. That is not an opinion. Car has not overheated, or shown any sign of doing so. It has not burped, or purged, or whatever.

1.4 bar, had to go look at it.

Here is the GAS solution. And description of how retarded 2.0 is.
https://www.germanautosolutions.com/...12_bar_cap.php

More discussions on retarded 2.0 caps.
Got the 1.2 bar expansion tank cap from German Auto Solutions - Bimmerfest - BMW Forums

Oh and just if you are bored, just google BMW 2.0 bar cap.

Hey man I'm well aware of the problems people have with cars. I'm not debating here , just stating facts. I never said the vehicle will overheat with a lower pressure cap. I said putting on a lower pressure cap lowers the overheating threshold.

In your case, was the expansion tank you installed oem or aftermarket? Was it filled properly? You stated maybe not so that kind of ends it there.

You also state that you have had no problems since you have changed to a lower pressure cap, new hoses, and tank, and everything is fine with no puking. Awesome. Now that you have your cooling issues figured out you can put your 2bar cap back on and all will be well!

Coolant doesn't compress. Air does.

Sometimes that is the case.

OE, as in from BMW at openroad.

I didn't overfill, but this is only my 4th bmw, so what do I know.

I also, did not do the radiator. Because I find that quite silly.

Again, our system cannot hold 2 bars, with brand new parts. All that plastic, especially hot, will not be able to make the cap relieve the pressure. Something else will explode first. This is the same reason BMW issued all the e30 guys 1.4 bar caps after they made a big enough stink about it. All the new BMWs also do not have the 2.0 cap.

If someone is willing to come by my garage, I will put 2 bars of air into your system, and prove a point. Even my coolant pressure tester, I struggle to pump up past 1.6 -1.7 bar. At 1.6, all the hoses feel like rocks. Not normal. Your coolant system does not operate at this pressure.

Ok genius, you explain why overfilling an expansion tank with coolant shouldn't be a problem with out using the word water heater :)