Steam from A/C dash vents

[Nautilus]

Hello everyone

Had a strange thing happening to my A/C today (very hot, 40ºC/104ºF day): after running some scores of miles through traffic, A/C blowing all the time, no problems, left the car for 1 hour into an underground parking lot. After restart, a thin white steam began to raise from the dash vents. Turned A/C off, opened the windows, ran for a few seconds, then restarted A/C - no more steam, normal operation.

It did not smell like G12 coolant, so a heater core leak may be ruled out.

There was a strange smell in the car for some time on humid days, like rotten grass. Just before steam begun to raise, the smell was there.

There was no exhaust leak or exhaust smell.

A/C blows very cold when needed.

For some time, the smell of "humid dust" when the A/C is turned off did no longer bother me as it did in the first few years of the car's life.

Does it sounds like condensation / water vapor mist due to very hot weather and very cold A/C evaporator, or more like a R134 leak?

And if there was a leak, why did steam blew only for an instant, and not in the previous hours of struggling against heat, or after the A/C was restarted?

Thank you,

~Nautilus

 

[Dan1720v]

You'll probably find it was actually condensation rather than steam.

 

[Nautilus]

The "rotten grass" smell may be due to some mold built up into the A/C? The upper side of the evaporator, beneath cabin air filter, was clean. Cabin air filter will be changed after pouring some A/C cleaner in the system.

R134 has a distinctive smell, which can indicate a leak?

~Nautilus

 

[Dan1720v]

AC gas smells just like a new fridge. if the ac is still working id say it wassnt a leak.

 

[domin8or]

I'd be happy to have that smell if i had 40 degree temps....more like 10 here....

 

[Muttley]

Condensation drain tube blocked, I'd guess. Does a puddle of water form under the car when it's parked?

 

[Nautilus]

Nope. Some water trickles down in a puddle if the A/C blows with the car stationary.

Found a small heater core leak: about 4 inch wet spot on the carpet in the right (passenger side) footwell. Pink G12 coolant, checked with a white tissue. Not enough to smell like coolant inside.

If such leaks happen, the most likely culprit is the heater core itself, or the hoses and ducts which lead to and from it? And the core can be accessed by removing just the passenger side under-dash panels, or the middle of the dash (console, climatronic etc) has to be removed as well?

~Nautilus

 

[Nautilus]

Found out in the meantime that heater removal in Golf Mk4 or Audi A3 (and therefore in our Leons which are closely related) means total removal of both dash and under-dash.

As I could not afford my dash (on which I've spent back-breaking months to wrap in eco-leather) to be butchered, sought a temporary fix:

Went to a nearby gas station and bought a radiator sealer (ERC brand, German made, "compatible to all coolants and engines").

Poured the sealer (a pink gunge) in 1.5 liters of distilled water (it takes minutes to dissolve, but I didn't wait so long) and poured it into the coolant reservoir. The engine block was already hot, at 90ºC.

Started the engine, put immediately the A/C to full heat ("HI") and fans to max rpm, then started the A/C compressor as well, to strain the coolant circuits under the maximum possible load. Left the engine to run at idle for 20 minutes. Checked periodically the coolant reservoir, opening the cap to eliminate the air bubbles from the circuit. Touched from time to time the wet spot on the carpet, it remained cold. Previously, when I've discovered the leak, it had been hot, so the coolant had been freshly leaked.

20 minutes later, spot still wet and cold. No more leaks. Coolant level steady in the reservoir. Windows which had misted themselves when engine started were dry by then.

Stopped the engine.

I'm going to top tomorrow the coolant with 1 liter of G12 to remake the ideal 50:50 mixture.

If dear God helps us, the leak (which had been more like a trickle) may be fixed from now on. Even if the thermostat, which is quoted to be very sensitive to radiator sealers, needs replaced. Otherwise there come days of labor, expensive parts and poor workmanship to fix back the entire dash.

I suppose the sweetish "rotten grass" smell had been due to a reaction of the leaked coolant with dirt and dust below the carpets and in the cracks and crevices of the bodywork, where it leaked, and I also deduce the leak had been intermittent throughout the last months, for the smell appeared only on humid days, or for 30 seconds or so after starting the A/C.

~Nautilus

 

[LEE69]

You can remove the matrix without removing the dash

 

[Dan1720v]

Found out in the meantime that heater removal in Golf Mk4 or Audi A3 (and therefore in our Leons which are closely related) means total removal of both dash and under-dash.

As I could not afford my dash (on which I've spent back-breaking months to wrap in eco-leather) to be butchered, sought a temporary fix:

Went to a nearby gas station and bought a radiator sealer (ERC brand, German made, "compatible to all coolants and engines").

Poured the sealer (a pink gunge) in 1.5 liters of distilled water (it takes minutes to dissolve, but I didn't wait so long) and poured it into the coolant reservoir. The engine block was already hot, at 90ºC.

Started the engine, put immediately the A/C to full heat ("HI") and fans to max rpm, then started the A/C compressor as well, to strain the coolant circuits under the maximum possible load. Left the engine to run at idle for 20 minutes. Checked periodically the coolant reservoir, opening the cap to eliminate the air bubbles from the circuit. Touched from time to time the wet spot on the carpet, it remained cold. Previously, when I've discovered the leak, it had been hot, so the coolant had been freshly leaked.

20 minutes later, spot still wet and cold. No more leaks. Coolant level steady in the reservoir. Windows which had misted themselves when engine started were dry by then.

Stopped the engine.

I'm going to top tomorrow the coolant with 1 liter of G12 to remake the ideal 50:50 mixture.

If dear God helps us, the leak (which had been more like a trickle) may be fixed from now on. Even if the thermostat, which is quoted to be very sensitive to radiator sealers, needs replaced. Otherwise there come days of labor, expensive parts and poor workmanship to fix back the entire dash.

I suppose the sweetish "rotten grass" smell had been due to a reaction of the leaked coolant with dirt and dust below the carpets and in the cracks and crevices of the bodywork, where it leaked, and I also deduce the leak had been intermittent throughout the last months, for the smell appeared only on humid days, or for 30 seconds or so after starting the A/C.

~Nautilus

And soon enough you'll have a completely blocked heater matrix.. Nice.

 

[Muttley]

It's not a certainty, Dan, as I've mentioned before.

In the distant past I've used both Radweld and Bar's Leaks on Imp and Mini engines - and would never use either compound again. Indifferent results with respect to fixing the leak, and ongoing blockage of the cooling system.

A couple of years ago I had a small radiator leak in my TDI 110. A friend who builds kit-cars (which tend to use older engines and whatever radiators will fit, so have more cooling system issues than most of us) recommended K-Seal. He's not one for "magic potions" either, so I took his recommendation seriously where I'd otherwise have gone for radiator replacement.

The K-Seal stopped the leak and caused no problems for the remaining life of the car, which was totalled in a non-coolant related accident caused by a white-van-man, for which he was to blame, and I got fully reimbursed by the insurance company.

So I would be happy to use K-Seal (and only K-Seal) again. But in general I'm sceptical of such things, just not as sceptical as Dan.

 

[Nautilus]

Had a 50 km run (city traffic) in the morning and another 30 km run in the evening.

Tested the HVAC system in all combinations imaginable, from HI to LO, from no fan to maximum fan speed, compressor on or off. No more smell of coolant, the level in the reservoir did not change by a fraction of an inch. Heater matrix heats, A/C (on which I've insulated the cold pipe) blows an air so cold it can freeze me out of the car.

Since the heater matrix is inside the dash HVAC unit and has a seal around, while the end tank is outside, and the sweetish stench came only from dash vents, this means the leak was in the matrix itself and not the end tank or pipes.

The trickling of the coolant over months each time while the A/C started suggests a small pinhole crack which opened at cold and closed itself under heat (the type of crack which comes from thousands of dilation-contraction cycles over the life of the car). Being so, it can be closed by the hardening of the gunge.

Previous experience with modern pressurized coolant systems (Mercedes-Benz W124, Lada 111 and VWs) tells a true crack, visible by naked eye, is completely impossible to seal. No combination of silicone, fiberglass, hose tape, JB Weld, Poxipol, or all of them together, can close it, once the 90ºC oily antifreeze flows over it, it still oozes out. The worst parts are radiator end tanks, and also the most prone to crack.

If the leak had been in any other part than heater matrix, the part would have been already changed this morning at the dealer.

~Nautilus

 

[Nautilus]

4th day. Still no discernible leaks. Coolant level the same. Tested periodically hot and cold settings of the A/C. No more rotten grass stench.

The clogging of the cooling system may happen if the gunk is exposed to air to harden itself. In older engines, heater matrix was separated from the cooling circuit by a mechanical tap, and once it closed, the car could be run practically with no connection between heater and cooling circuit. Most modern engines and practically all engines with Climatronic generate cabin A/C by mixing hot air from the heater matrix and cold air from the evaporator and therefore should have permanent circulation of the coolant fluid through all the system, so it's more difficult (but not impossible) to have pockets of air inside.

~Nautilus

 

[Nautilus]

5th day. No discernible leaks. No smell of rotten grass with A/C on, just a short whiff when starting the car. Coolant level down by 2-3mm in the reservoir, topped with maybe 100ml of G12 to be safe. Carpets dry.

After some time, if there are still no leaks, coolant should be drained and replaced to be sure no clogging may happen.

~Nautilus

 

[Nautilus]

10th day. No discernible leaks, the whiffs of smell diminished to nothing. Car usually runs with A/C on 24.5ºC and compressor on.

If there is no leak after 1 month, I drain and replace the coolant with fresh G12 myself.

~Nautilus

 

[akchappers]

I put rad weld into my lpg cupra as it had a small leak in the system and that was nearly two years ago now and still being driven at 11 tenths and all is good even after remap!
Ak

 

[Nautilus]

2 months and ~ 4000kms later.

No discernible leaks, sometimes a vague whiff of sweetish smell which disappears after a few seconds. Heater blows burning-hot air on "HI" if checked. A/C runs well. Never tried anymore to strain the A/C on coldest possible setting in 40ºC days, held it on 24.5ºC setting permanently. Coolant level raises and lowers as it expands and cools, but did not fall below minimum mark. Constant 90ºC engine temps.

Should (part of) the coolant with dissolved sealer be drained and the system topped with fresh coolant to prevent clogging?

~Nautilus

 

[Nautilus]

2 1/2 months and 4500 kms later.

No discernible leaks, no more sweetish smell, heater blows hot air if switched, constant 90ºC engine temps. Climatronic left on 24.5ºC setting. Slight fogging (wet to the touch) of the windshield during morning run when warm air is blown into the cabin. The defroster blows it away, but slowly. No fogging on side windows. There is no coolant smell through either vent when this happens. Wet windshield has no smell.

~Nautilus

 

[Nautilus]

5 1/2 months later.

There was no discernible leak or decrease of the coolant level in the mean time. No more sweetish smell, heater blows hot air if switched, constant 90ºC engine temps. Sometimes a bit of window fogging. There is no coolant smell through either vent. Part of the coolant drained and topped with fresh G12-water 50:50 mixture, but not much.

As we can see, the gunk worked.

~Nautilus

 

[Nautilus]

1 year and 13 000 kms later.

Still no coolant loss incident yet, heater core gave heat over winter just as before. Also cleaned the HVAC air ducts and radiators with foam spray to get out the dirt and coolant residue. Some of the gunk ended up in the coolant tank and got removed with a small long-handled brush.

A funny thing happens with coolant level in the tank, sometimes it falls much below minimum in short city trips and raises over maximum in highway runs (or after air in the tank is released by removing cap). The blinking red light on the dash does not indicate low coolant. Coolant level sensor will only be triggered when "the basket-like thing" (where coolant level sensor wires stay) gets dry and leaves the two wires dry, as long as the coolant level oscillates and the wires stay wet it does not react. Completed a few times with 50:50 mixed G12 coolant over time (about 1-2 coffee-cups of coolant each time, add themselves up to more than 1 liter over a year), scared by low coolant levels. Engine temps constant 90ºC on the dash.