[WrxToBeamerGuy]

Ive had this issue multiple times on my 2016 B58 and getting a new cap fixed it each time for some period of time until the O-ring doesnt seal properly then I get a new cap again. This latest cap has lasted me 6 months without coolant levels lowering at all.

[AMG KLR]

Originally Posted by WrxToBeamerGuy

Ive had this issue multiple times on my 2016 B58 and getting a new cap fixed it each time for some period of time until the O-ring doesnt seal properly then I get a new cap again. This latest cap has lasted me 6 months without coolant levels lowering at all.

Do you find that the cap is "bad" when it is noticably difficult to remove and feels "tight"? My auxiliary cap (the smaller one) is butter smooth. The other main expansion tank feels tight and I could swear that last time I replaced the cap it went on and off a lot easier with the fresh cap installed until as of recently

[quixotemi]

Try using a small amount of foodgrade lubricant on the o-ring before putting it back. I experienced the issue once: did a coolant flush and got new caps (put a tiny amount of lubricant on the o-ring), and haven't had an issue since.

[WrxToBeamerGuy]

Originally Posted by quixotemi

Try using a small amount of foodgrade lubricant on the o-ring before putting it back. I experienced the issue once: did a coolant flush and got new caps (put a tiny amount of lubricant on the o-ring), and haven't had an issue since.

I did the same.

[BaconDouble]

Are you all getting an OEM caps or aftermarket ones? Is there any noticeable difference in the BMW part vs Vaico, Febi, Rein, etc as far as "fixing" the problem goes? Should replacing the cap be done on a regular basis (every 50k miles for example?)

What would you suggest as a foodgrade lubricant?

[quixotemi]

Originally Posted by BaconDouble

Are you all getting an OEM caps or aftermarket ones? Is there any noticeable difference in the BMW part vs Vaico, Febi, Rein, etc as far as "fixing" the problem goes? Should replacing the cap be done on a regular basis (every 50k miles for example?)

What would you suggest as a foodgrade lubricant?

I got these since they were on sale:

https://www.fcpeuro.com/products/bmw...ap-17117521071

https://www.fcpeuro.com/products/bmw...ap-17117639024

Super Lube makes good stuff: https://www.amazon.com/Super-Lube-21...54&sr=8-4&th=1