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Lately my car has developed a stink, I wondered whether anyone might have some ideas to fix it.
When the heater is running it's giving off a really strong vomit smell!
The car doesn't have A/C but I tried one of the A/C aerosol sterilisers but that hasn't fixed it. I've sprayed sterilising spray into the vents too, but it hasn't helped.
The cabin filter was replaced in 2024 (3000 miles ago) and looks fine.
I'm totally stumped...
Something damp in the car? Check under the cabin carpets and the boot liner...
Something dead in the car?
FTFY
Is there any evidence of coolant use? Keep an eye on your coolant level as a leaking heater matrix will smell although it's a sweeter smell rather than vomit.
Dead thing under bonnet?
Or around the air intakes.
what car is it? Might help with faults that are specific to make/model.
Golfs/Leons/Octavias of a certain vintage had the cabin filter in a compartment under the windscreen and if the filter wasn't seated properly or the cover put back quite right at a service could lead to the ventilation system filling with water for instance. But generally check along the bottom of the windscreen for anything that might be loose or not seated properly that might be letting water get in.
Look for where the air is getting drawn into the ventilation system too - is there a build up of crud, soggy leaves etc close by?
Also feel around the carpets and check if anything's wet - running the ventilation heating might be stirring up bad smells from that. Water can travel a fair distance from the source of the leak - we had water in a rear footwell that was getting in through a failed seal in a front door
is the car prone to steaming up?
Thanks for the suggestions so far.
It's a 1st gen BMW Mini.
I had a good look around the scuttle vents for rotting leaves or mouse carcasses a few weeks ago, but there was nothing there. Although I suspect the scuttle vents are more for engine cooling rather than where the air for the cabin comes in. Not sure where the actual cabin air intake is.
Carpets seem fine, and it's not especially prone to steaming. I'll double-check coolant levels tonight - it's def not a sweet smell though, you'd honestly think someone had thrown up in there.
From a bit of googling and youtube, it looks like the cabin air intake is behind the battery. I'll have a rummage around there tonight too.
The cabin air intake is behind the battery. The filter is replaced thru the glovebox (actually it probably won’t on a RHD car)
You’ll probably have to remove the cowling to get access. It’s in 2 pieces and you only have to remove the smaller piece above the battery.
Leaves / road debris can also gather behind the wheel arch liners. Easy removal - wheel off and then it’s a T30 and some of those automotive fasteners.
There’s a lot of good forums on Mini’s.
Being a mini your problem is likely to have been a problem for someone else previously 😂
Manky windscreen wash tank? My SIL had a mini that seemed to turn rancid green. I suspect she had put lots of plain water in rather than washer fluid. It STANK when you sprayed it. I took off the bottle lower pipe (a pain the arris...) and cleaned it LOTS.
Manky windscreen wash tank? My SIL had a mini that seemed to turn rancid green. I suspect she had put lots of plain water in rather than washer fluid. It STANK when you sprayed it. I took off the bottle lower pipe (a pain the arris...) and cleaned it LOTS.
Unlikely to be that, as I removed, cleared and refitted it earlier in the year with water and fresh washer fluid, for unrelated reasons. Although now I think about it MissV mentioned the other day that she thinks it coincides with the washer jets being used. I'll have a play with that too...
Oh yeah, I had a Volvo S40 with a stinky washer bottle, bloody awful. I used to drop in sterilising tablets to keep the water "fresh" although in the end it needed removing and the sludge clearing.
SIL mini was a Mk1 BMW one as well...
Failing or bad catalytic converter can smell like sulphur or rotten eggs.
Has anyone split milk in the foot wells or boot! As that'll smell like puke once it starts to go off ...
Had a bit of an investigation last night - ended up a bit more of an ordeal than planned (everything I touched seemed to fall into the engine bay taking ages to retrieve).
So... Battery and battery box out. No evidence of rotting leaves/carcasses near the air intake.
Coolant expansion vessel has always looked ok, but after popping the lid off it turns out that I've not been looking at a fluid level, it's a scum mark around the expansion tank! It turns out the expansion tank is empty and has some sludgy looking scum in the bottom!
I've had the car 4 years and it's not had a coolant change in that time, so looks like it's long past time for a flush and refill.
I'm assuming the smell is sludge working it's way around the system and into to the heater matrix - I guess that could explain why I don't smell it all the time.
Not sure where the fluid has gone though. I checked the oil and that all looks normal, so it's not making its way into the engine. I guess it could be gradual evaporation, the expansion tank lid doesn't seem like a solid fit.
Pinhole leak in the radiator, spraying gunk onto something hot so it evaporates and then gets pulled into the cabin air intake?
Not on a car but I had a weird leak on my motorbike radiator, only opened up when the engine was up to temp and went directly onto exhaust headers so any evidence was evaporated away. When cold it sealed so there were no drops on the garage floor. Took a while to find...
Has anyone split milk in the foot wells or boot! As that'll smell like puke once it starts to go off ...
mrs_oab spilt some on the day before we loaded up for 2 weeks in the heat of a south French summer... *boak*
Not sure where the fluid has gone though. I checked the oil and that all looks normal, so it's not making its way into the engine. I guess it could be gradual evaporation, the expansion tank lid doesn't seem like a solid fit.
If the cap isn’t holding pressure, that may be your answer.
The coolant cap is often overlooked, they usually have a pressure relief rating. The coolant boiling point will be lower if the cap leaks or isn’t done up.
My wife’s MK7 Golf had the heater wiring start to melt, this manifested itself as a horrible acrid smell with the heater on, I would say was quite like vomit in fragrance.
Almosr certainly not your problem, but Brie cheese which has fallen out of a shopping bag and found its way under the boot floor smells like a corpse after a few weeks
I think mk1 BMW mini expansion tanks used to crack/leak? It’s probably been replaced by now anyway, but was something I looked for when we had our Cooper S.
Not sure where the fluid has gone though. I checked the oil and that all looks normal, so it's not making its way into the engine.
For future reference that just means it's not got I to an oilway... Doesn't mean it's not got into a cylinder.
But there's lots of places for coolant to leak out slowly.
My cayenne had a slow coolant loss that took the dealer 3 visits to locate and even then it was only when they ran the car up on the lift for half an hour did they smell antifreeze.
I'm assuming the smell is sludge working it's way around the system and into to the heater matrix - I guess that could explain why I don't smell it all the time.
It's a sealed system. Coolant leaks in my limited experience have a vaguely sweet curry smell to me, definitely not vomity. If the heater matrix was leaking then I think that you'd struggle to demist the interior
In a central heating system reactions form sludge, gassing and a pressure build-up, dunno if that applies to the different chemicals and materials in a car though
Get the system pressure tested by a garage (or you can buy a test gadget for under £20) before you waste money on new coolant in a possibly leaky system
My feeling is an external cause, something spilt, water leak soaking insulation, that kind of thing. Our fleet garage always treated AC systems with some citrus smelly stuff, here's an example https://bilthamber.com/product/air-con-bomb-citrus/
I flush my washer bottle with clean water every spring and don't bother with washer fluid until autumn
In a central heating system reactions form sludge, gassing and a pressure build-up, dunno if that applies to the different chemicals and materials in a car though
yeah.... different metals involved.
Coolant leaks in my limited experience have a vaguely sweet curry smell to me
That's the antifreeze I believe.
One other thing to be aware of, but this won't be the cause of the smell, is that cars sometimes have a bag of silica gel in the expansion tank. These can sometimes break apart and, from what I've read, can potentially clog up the heater matrix.
Thanks for the various comments, it gives me a bit more to go on.
Current plan is to do a coolant change, it's def overdue, and I've no idea how long it's been low (what better way to spend boxing day), then monitor a) the smell b) the coolant levels.
To cover a few comments/questions...
- I'm certain there's nothing spilt/lost inside the car
- From what I've seen there's no silica gel in the expansion tank on this model
- I think the cracked expansion tank problem is more of an issue on the "S", this is a One, but I'll def give it an inspection when cleaning it out
- The cap on this expansion tank just clips on, it's not a screw on one, I think it's specifically designed that way - looks like this
I'd be mistaking that for the washer reservoir, glad they put a sticker on it 🤣
