TheSamba.com :: View topic - Coolant Smell

Mon Jul 14, 2025 7:26 pm

I have always had a mild coolant smell when running my heater, I can't pinpoint where exactly it comes from, and I can smell it outside the van as well. Additionally, I have to occasionally add a bit of coolant to my system to keep it topped off.
Quite a while back I replaced the hoses in my heater circuit with blue silicone hoses. I did this when I installed a SmallCar in dash AC system. I know the odor is related to the heat system because I only get the smell running the heater. A littler more than a year ago I repainted the van and while doing so pulled the heater/AC suitcase and sent it back to SmallCar for testing. It came back with a note that it was fine, no leaks.
I was just reading about silicone hoses as I need to refresh some of the engine compartment hoses (I have a 1.8T) and learned that silicone hoses are semi-permeable and will leach some coolant. Some more than others.
Doing a Samba search there are numerous threads with folks smelling coolant but not finding the leaks.
I suspect that my odor is from the heater hoses as they run both outside and inside the van. They are also a matte finish, probably Amazon purchase of unknown (at this point) origin. I think some of the higher-end silicone offerings for radiator hoses and such have an outer coating that makes is less permeable, but that the hoses I have, basically stink. Sooooo, I was wondering if there are any other Sambanistas who have a low level coolant odor issue and if you do, are you running silicone hoses?

Mon Jul 14, 2025 10:53 pm

Only when the rear heater is running (stock type hoses).

According to my kid's friends, it smells like maple :lol:

Note, I don't loose any coolant, and the tank pressure holds for weeks.

Tue Jul 15, 2025 12:37 am

There is a huge variation in olfactory sensing in people, especially with regards to coolant odours. My partner can detect a nanogram of EG in a barn so I rent her out as a leak detector, whereas I can’t tell EG from beer without tasting.

Tue Jul 15, 2025 12:42 am

The rear heater valves tend to leak, in particular where they mount to the heater and the core can leak as well. There is a reason so many people end up removing these units. The coolant ends up under the padding for the carpet where it can't be seen, but permeates the cab with the smell of antifreeze.

Tue Jul 15, 2025 4:56 am

I have checked numerous times for leaks, the heater valve with the smallcar is outside below in the spare tire well. I do have a very sensitive schnoz. Plan is to replace the lines and see if the smell goes away...

Tue Jul 15, 2025 6:16 am

dougnlina wrote: I have always had a mild coolant smell when running my heater, ... <snip> A littler more than a year ago I repainted the van and while doing so pulled the heater/AC suitcase and sent it back to SmallCar for testing. It came back with a note that it was fine, no leaks.

if you smell coolant when using the heater, there's a 99% chance the heater core is weeping. how did SC 'test' the heater core? shop air pressure and watch for gauge fall? shop air pressure with core submersed in water? were the heater box clips even disturbed? without knowledge of exactly how they tested, i'm inclined to think they kept the box assembled, put shop air on it, and watched for gauge fall. i haven't come up with a reliable way to test these cores that also accounts for heat expansion.

it takes an extremely small leak to release the characteristic ethylene glycol odor. in my van, i get an initial smell that goes away once the core has been hot for a few minutes. my guess is that a small amount of coolant weeps builds up on the core when the valve is off, then when the water valve is opened, the core gets hot and releases a temporary flood of odors as the hot coolant evaporates.

the good news is that these cores do not seem to fail catastrophically. they are assembled with folded metal ears pinching the glass-filled nylon header tank against a resilient neoprene seal. or at least it was resilient 40 years ago. in the cores i've looked at, the leaks are not from the coolant tubes but from this juncture of plastic header and aluminum body.