F80 Coolant Leak from IC Reservoir

[Nanometer]

Hey there!

Could use some help with my 2017 F80.

Background:
I walked into the garage today and noticed that after a week of not driving my F80, keep that one week time frame in mind, that there was a puddle of fluid on the floor. Thought it was oil, and did the taste test and it was actually coolant. I looked under the hood and noticed that the intercooler cap was leaking which is odd, so I loosened it. As I continued to loosen it the cap released a significant amount of pressure. Mind you again, this car hasn't been driven in a week.

Question:
What on earth could cause this condition? Has anyone seen this before? Why would the system be under such enormous pressure? This can't be normal since its just a coolant system. And that the car was cold for such a while. Never seen this behavior before and I am hope it is not something serious. Hoping one of you can help!

Edit: I have opened the reservoir cap every couple days and I keep discovering pressure in the system. I do not believe this is related to hot and cold weather, or could it? I am noticing a lot of pressure build up, and it seems excessive... just looking for clarification. Perhaps I need a new reservoir and or cap?

[JAI///M3]

Taste test? lol

My guess is the Intercooler is leaking and boosted charge air leaked into the water circuit and pressurized it.

[Nanometer]

lol yes... my auto tech teacher in highschool said oil tastes different from coolant

And thanks for your input, that makes so much sense. Bad intercooler? bad gasket do you suspect? Is this a common failure?

[s55jesus]

Originally Posted by Nanometer

lol yes... my auto tech teacher in highschool said oil tastes different from coolant

And thanks for your input, that makes so much sense. Bad intercooler? bad gasket do you suspect? Is this a common failure?

Undo the J pipe portion and see if there is coolant leaking into there. I had mine leak last year with only 37k miles on the car.

[RElias21]

Originally Posted by Nanometer

lol yes... my auto tech teacher in highschool said oil tastes different from coolant

And thanks for your input, that makes so much sense. Bad intercooler? bad gasket do you suspect? Is this a common failure?

https://f80.bimmerpost.com/forums/sh...570544&page=28

[Nanometer]

So new issue.

Every two days I have opened the coolant reservoir pictured above, and a significant amount of pressure has built up in the system. Now I do understand it gets hot and cold during day and night respectively, but I feel that this is significantly more pressure than there should be. Any ideas? I do not believe I have an intercooler leak, as if the car was sitting and since having been the reservoir cap removed several times to relieve pressure, there is no boost to charge the system.. Any ideas? This has me stumped...

[paulo_f80m3]

Originally Posted by Nanometer

So new issue.

Every two days I have opened the coolant reservoir pictured above, and a significant amount of pressure has built up in the system. Now I do understand it gets hot and cold during day and night respectively, but I feel that this is significantly more pressure than there should be. Any ideas? I do not believe I have an intercooler leak, as if the car was sitting and since having been the reservoir cap removed several times to relieve pressure, there is no boost to charge the system.. Any ideas? This has me stumped...

Check the intercooler for leaks by pulling it off the J-pipe. That is a low pressure system. I just replaced mine as a preventive of them failing and I performed a level check right after a 100+ mile trip. I took the cap off with ease and the level was perfect.

[hellokitty]

Just replaced the small tank, cap, intercooler and engine side coolant reservoir for good measure.

My small tank and intercooler was leaking. 2017 with 50k miles.

[ringo9]

New to all this as I recently bought a F80 but seems coolant leaks are so common (that other thread is 30+ pages long) that is already giving me more worries than I would need...

After those reads I decided to go and check my coolant level and... wouldn't you guess, it's sitting a few mm below the MIN of the plastic stepped yellow gauge.

However, the reservoir I mean is not the one pictured by the OP here, I believe that one in the picture is "secondary" reservoir for intercooler loop?

So my main one at the front was low, does that automatically mean I have an issue considering I don't know when it was the last time it was topped up? Is it normal for these engines to consume some coolant or the level should stay at MAX for life? Shall I just top up and monitor over the next weeks?

Another thing, I also checked the back reservoir, the one further back was much harder to open, I used a strap for oil filters, there was a little bit of hissing when I opened it, but the level was on MAX on that one. Now I worry if I should have ever opened that and introduced air, but since it has instructions on how to check for min/max i guess it is meant to be opened?

[Nanometer]

turn out to be the radiator cap, probably the seal went bad. not sure why as it has been untouched.. but there you have it!