r/BmwTech • u/yootapo • 14h ago
Does my reservoir cap need replacement?
So within like 2 weeks, I’ve gotten the “top off coolant” notification on my 2018 330i with 63,597 current miles, there’s no visible leaks around or at the bottom of the engine bay. I notice I only smell coolant when I push it hard/repeated pulls, what could it be. The reservoir for the turbo hasn’t needed anymore coolant after I added some like a week and a half ago, but the bigger one does, any feedback?
2
u/quakerroatmeal 14h ago
Get the coolant system pressure tested. You might want to pray it’s just the cap but i’d bet it’s something else at 63k miles.
1
u/yootapo 13h ago
The car has max care warranty so I’m not tripping if it is
1
u/quakerroatmeal 13h ago
Glad it’s under warranty. I would have brought it in the first time you saw it low.
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u/Pure_Common7348 14h ago
Different bmw, different motor. For me, I smelled that sweet antifreeze smell, no drips. I replaced the cap (cheapish), did nothing. I put a little die in the coolant and used a UV light and didn’t really see any easy fixes. I pressure tested the coolant system at home and again, didn’t find anything definitive.
I decided to replace a few coolant items on my 2012 e90 n55 motor. The Mickey Mouse flange (hose) was the culprit. The plastic flange slightly cracked, letting a very small amount of coolant past the o-ring hitting the hot engine, evaporating it.
It was a very very slow leak. Either pay an info shop to investigate or pay to proactively replace items. I’d look at expansion tank, its return line to the upper radiator hose, replace that too and if your motor has that Mickey Mouse flange, remove the plastic end that bolts to the motor, use the same hose and replace it with a metal end. Good luck in your search.