[Toaster_79]

Hi everyone, happy to be on the forum!

Just wanted to share my experience with our lovely cooling system in the hopes future researchers can learn more about the issues that I currently face and deal with half, if not a quarter, of the overthinking.. lol. I've owned my '12 E92 335 for almost a year now, and I've been chasing down a small but consistent coolant leak for the past month or so since I started to notice a little puddle on the right front passenger side. I've gotten the low coolant warning multiple times, so now I'm always keeping some on me. With that, I've been slowly ruling out the usual suspects despite not being too mechanically inclines nor having access to the undercarriage. I took it to a trusted mechanic friend of mine who replaced the overfill tank, the Mickey flange, and the hose going from the thermostat to the cylinder head. I don't believe it's the turbo lines nor the thermostat because I have 0 codes and everything runs just as it should, except the leak.

While there were a few tiny holes in the old hose that had white spots I still found myself a few days later with the SAME puddle. Pretty annoying. I only found out later because it's been raining the past weekend, like every weekend.

I put some cardboard out underneath it tonight and found the puddle again, so I stuck my phone right on top of it and took a few pictures to find the drip originating from what I believe to be the coolant inlet hose. To my knowledge - it's 11537584550 for a 2012 N55. While I'm not convinced it's the pipe itself because it's metal, I'm leaning more towards either the water pump cracking and leaking a bit or the O-ring somehow is letting coolant by, or both. I have an appointment with another BMW specialist on friday, and I'd be honored to share whatever insights I can gather regarding this issue. My hope is it's the water pump as it's covered under my warranty, but has anyone seen something similar that's indicative of my suspicions? The car had the water pump replaced at 46,829 miles and I'm at around 76K now. I know they like to go randomly, so anybody's horror stories are welcome here.

I appreciate in advance anyone willing to share.

[Toaster_79]

Replying here just with a follow up for anyone facing a similar issue.

Car's been dropped off at a reputable shop for the past few days, and after a pressure test it was revealed that my hunch was right. The coolant inlet hose WAS leaking, but it wasn't because of the water pump but rather the O-ring that sits inside it. They found it, replaced it, and I shouldn't have any more issues with that at least. I hope this helps someone in the future and saves them a couple bucks - I'm just lucky I had some warranty left!!

[Mikacina]

Hi. I know this post is from 2023 but your situation seems exactly like what I am currently experiencing. If you happen to see this, I'd like to ask if you noticed coolant dripping down onto the downpipe and evaporating? If this was the case you'd also notice smoke after driving for a while (at least in my case).

[Toaster_79]

Originally Posted by Mikacina

Hi. I know this post is from 2023 but your situation seems exactly like what I am currently experiencing. If you happen to see this, I'd like to ask if you noticed coolant dripping down onto the downpipe and evaporating? If this was the case you'd also notice smoke after driving for a while (at least in my case).

I hadn't noticed anything on the DP, nor had I ever seen any smoke - just puddles everywhere I went. I'm not sure if it's a factor but I was also missing my transmission cover at the time which I suppose made the leak more prominent because it followed me whenever I parked. I had tried all the usual suspects and without the ability/opportunity to get actually under the car at the time I just put my phone on with flash and put it facing upwards right on top of the puddle. Turns out it had worked in identifying the leak's source (that O-ring) and I hadn't noticed it in the pics until I got it back from the shop. Have you checked your connections/rings? It could be from a few places (water pump, thermostat, various hoses)