Occasional Coolant Scent

[Voscilation]

Every now and then I get the occasional whiff of coolant when my windows are down and I'm sitting at a light or when I park but only after turning the engine off. No drips, stains, puddles or hissing. No spontaneous milkshake machine installation in the engine bay nor a free fog machine from the exhaust.

When this first happened I checked my coolant and noticed I was low and marked it as I didn't have any on hand. Never had any warnings or even the slightest increase in temperature, even when driving non-stop for 12 hours. I even sat parked on the interstate one day in 90deg. F temps for about 25 minutes in sport plus (yeah yeah) and actually watched my oil temperature drop to 190deg. F. Coolant arrived and I was a cup low.

It's the former E39 owner in me, but that sweet sweet aroma only lingers for the faintest second before leaving my grasp...I mean uh...has anyone else experienced this?

[Soul Coughing]

I had this issue with my car, and the dealer eventually replaced my radiator. The car still has the occasional coolant smell, but ive been checking the overflow tank on both and i havent seen a measurable drop. The usual suspects are a cracked radiator, leaking cap, or the overflow tank. All of those have been checked and the smell still exists, so I'm guessing it may be a connector somewhere deep in the depths of the engine.

[Voscilation]

It could be a leaky cap as I noticed some coolant residue around the filler when I first checked. Cleaned it up and none has formed since, overfilled when new/last checked maybe. Radiator and coolant tank are all good. I’ll continue to keep an eye on everything, not worth spending the money to diagnose when there’s no issue other than parfum de BMW.

[Imperial328i]

For what it's worth, every European direct-injected turbocharged engine I've owned has had a little coolant scent from time to time. I've stopped worrying unless I see puddles.

[Voscilation]

Originally Posted by Imperial328i

For what it's worth, every European direct-injected turbocharged engine I've owned has had a little coolant scent from time to time. I've stopped worrying unless I see puddles.

Cheers! Good to know it's not just me and my E39 past. Chalking this one up to "normal"

[Wanted_M]

A few things, check around the seam of your coolant reservoir, these are notorious for leaking overtime as they split/leak once they get hot. Check your water pump too with a mirror, once they start leaking thru the weeping hole you'll get a faint coolant smell and some residue.

[Voscilation]

Originally Posted by Wanted_M

A few things, check around the seam of your coolant reservoir, these are notorious for leaking overtime as they split/leak once they get hot. Check your water pump too with a mirror, once they start leaking thru the weeping hole you'll get a faint coolant smell and some residue.

Coolant reservoir is nice and clean, no leaks there. I was unaware of the water pump's weep hole potentially leaking. Taking this would be it (circled in red)? Doesn't look like there is any residue of sorts, just normal aluminum corrosion that's present on miscellaneous bits and bobs. What's interesting is the flaking paint on the crank pulley/harmonic balancer (EDIT: pretty sure that's the harmonic balancer. Drives the water pump). NOT the belts. The belts are looking fine. I'll continue to keep an eye on things and I'm soon due for an oil change + will mention it to the dealer. Will definitely want to get this sorted while still under warranty.

[jfritz27]

Originally Posted by Voscilation

Coolant reservoir is nice and clean, no leaks there. I was unaware of the water pump's weep hole potentially leaking. Taking this would be it (circled in red)? Doesn't look like there is any residue of sorts, just normal aluminum corrosion that's present on miscellaneous bits and bobs. What's interesting is the flaking paint on the crank pulley/harmonic balancer (EDIT: pretty sure that's the harmonic balancer. Drives the water pump). NOT the belts. The belts are looking fine. I'll continue to keep an eye on things and I'm soon due for an oil change + will mention it to the dealer. Will definitely want to get this sorted while still under warranty.

It's hard to get the perspective of exactly what I'm looking at with this shot, but what is that mass of structures appearing right below your red question mark? Something doesn't look right there....

[Voscilation]

Originally Posted by jfritz27

It's hard to get the perspective of exactly what I'm looking at with this shot, but what is that mass of structures appearing right below your red question mark? Something doesn't look right there....

That was exactly my first though when I saw it too. It's the crank pulley/harmonic balancer. Arrow is pointing to approximately where the photo is looking down at. Hard to get a good shot lol. The paint flaking off looks normal however. Here's a photo of a new engine (either crate or pre-production display) and you can almost see a faint cross-hatch pattern where the paint is starting to flake by the barcode. The question is: do they just flake off with time or is the water pump weep hole (circled to the left of previous post) dripping coolant onto it and taking some of the paint with it, not that the second option makes any sense.

[Voscilation]

It’s a few days shy of 6 months. I’ve smelt the smelly smell a few times since, but most likely less as the cold NE days preclude me having my windows down. Anyway, 6ish months and ~7,000 miles later I check coolant levels, down by maybe a 1/4 cup. No puddles, no residue, no white smoke. Everything is golden?

As a side note, sport plus oil temperature acts very very differently when it’s below 45°F out, it won’t try to target the 190°F I’ve seen it do in the summer. Can’t wait to get summer tires back on.

Cheers!