[rgh0]

I drove my 2013 V8 TDI R line to the snow on Friday night at Mt Hotham in Victoria last weekend for some skiing for the first time since I got it and Covid closures of ski resorts ended

Temperatures got down to around -3 C to -5C over night and when I left on Sunday there was a 20cm diameter red coolant spot in the snow under the car inside the LH front wheel and behind the axle roughly in line with the edge of the inner wheel arch panel

There was no measurable coolant loss in the header tank at the time and no further loss in the last few days having returned to Melbourne and 5 to 10 degrees C overnight minimum temps.

My presumption is that a hose to pipe connection in the area of the leak was the cause due to the alloy pipe shrinking in the cold weather and the spring clip clamp not maintaining sufficient compression on the hose resulting in a small leak. The car has the 4 zone heating / cooling and I believe there are coolant pipes that run back into the cabin rear heater system in the area of the leak behind the plastic inner wheel arch panels.

Has anyone else experienced similar issues ?? Heading up to the snow again in a few weeks and will take some spare coolant and if it occurs again I will investigate the potential source further.

cheers
Rohan

 

[SaVAGeSoot]

My presumption is that a hose to pipe connection in the area of the leak was the cause due to the alloy pipe shrinking in the cold weather and the spring clip clamp not maintaining sufficient compression on the hose resulting in a small leak.

Not a chance. Dream up some other crazy variant of this story.

 

[rgh0]

Thanks SaVAGe ....so do you have an alternate theory on what caused the leak to come and go overnight and not to reappear again so far ?

 

[SaVAGeSoot]

I don't have a magical diagnosis for you, but you should probably look closely in that area. Your leak did not fix itself, even if you don't see any evidence of it. Are you certain it was coolant? Get yourself a cheap borescope and poke around everywhere.

 

[volkswagens-for-life]

Are you positive it was coolant? No idea which g12 or g13 you're running but the new stuff is pink I think. Did you play with the substance between your fingers? Coolant is slippery but not like hydraulic fluid which would be brakes or steering

 

[chewblekka]

Remove fender liner, pressurize cooling system and have a good look. Pretty simple diagnoses.

 

[rgh0]

"Are you positive it was coolant? No idea which g12 or g13 you're running but the new stuff is pink I think. Did you play with the substance between your fingers? Coolant is slippery but not like hydraulic fluid which would be brakes or steering"

Yes sure its coolant. I use Nulon coolant which is an Australian brand owned by Fuchs and G12 compliant. The pinkish red stain was in the snow under the car and hard to test slipperiness as it dissolved in the snow which says it was water based and it was not oily like the red Penrite transmission fluid ( Toyota and VW compliant for the 7P 8 speed Aisin) or the redline red coloured diff and transfer case oils I use ( the best you can use in my opinion). The brake and power steering fluids are not a bright pink / red colour and would also be oily and not dissolve in snow

Remove fender liner, pressurize cooling system and have a good look. Pretty simple diagnoses.

Yes I have a full coolant system set of test tools and that's my plan to do next Saturday morning when the engine is cold and temperatures will be around 5 C. But when the engine is hot and should be under normal operating pressure I see no leak. Hence I will test cold and also will test cap relief pressure to confirm it's actually relieving at the right pressure

There are some posts for other types of cars with alloy coolant lines about this sort of leak being reported but I could not find any specific for for Touaregs and it looks like no one active on line on this forum has had anything similar occur. My previous Landcruisers used steel rigid coolant lines in places joined by rubber hoses to the heater and I never experienced anything like this. The use of spring clips on small bore aluminium to rubber hose coolant lines is common now in car design but this is mainly around keeping pressure on the rubber despite rubber creeping over time under the clip to prevent leaks.

Unfortunately I can't dream up another crazy theory on why it should leak like it has, other than my presumption around the pipe itself contracting and contributing to loss of seal in cold temperatures, despite a mechanical engineering degree and 50 years of piping system design in many different industries and it appears no one else has any theory or any experience in this problem either which is fine I will continue to investigate as recommended to find the root cause if I can.

cheers
Rohan

 

[SaVAGeSoot]

The coolant circulation pump is in that area.
You said 4 zone, so you probably even have the aux heater.
Dreaming that a 10-15deg temp change is sufficient to contract the pipe enough that its diameter reduces more than the spring clamp can compensate for is pure craziness for anyone who can spell engineer.

Let's spin it this way.... based on your "theory", what about those of us here in Canada (or others in Sweden\Norway\Russia) who regularly drive at temps of -20 or more? Are you suggesting that our pipe alloys are different or that we are also dropping coolant like that because of the temp swings?

 

[rgh0]

I agree that compared to other locations my low temperatures are not low. But my car is also 9 1/2 years old and has spent most of its life in high temperatures ( may be the first time its ever seen below freezing in its life) so potentially the hoses have gone hard and the spring clamp and hose cannot contract sufficiently to maintain the seal in this case .... who knows.

A pump seal leak would occur under pressure regardless of temperature in my experience as its due to a seal face failure due to wear or a seal bellows failure or a seal spring failure ( gets more complex with pressure balanced seals but these not common in car coolant pumps) and this appears not to be the case ... I have spent a lot of time on mechanical seals over the years where unexpected failures can cost you a million dollars + a day

cheers
Rohan

 

[SaVAGeSoot]

Dumb it down! You are overthinking!
All this stuff is in that area behind your wheel\liner. The Touareg's HVAC system is complex and smart. It is very possible that you do indeed spend most of your time in warmer climates where the systems don't need to isolate\activate\enlist all the components\pre-heaters\separate heater circuits to perform the thermal management as per design, and that your recent venture into colder climates actually revived some of these after a prolonged time of being dormant, simply because you now had a "request" for the additional functions\features.

 

[rgh0]

could be .. and in all that complexity ( is it all really necessary ?) there is a leak somewhere at low temperatures.... at least once in my experience ... testing will reveal more in time...... but so far no more leaks

 

[SaVAGeSoot]

( is it all really necessary ?)

I dunno... is it really necessary that you get quick warmups, quick cabin heat, quick window defrost, etc.?

 

[volkswagens-for-life]

I dunno... is it really necessary that you get quick warmups, quick cabin heat, quick window defrost, etc.?

Fair

 

[rgh0]

In Australia a lot of that stuff not anywhere as important in Canada

While the Treg 4 zone climate control system is very stable and well controlled the actual cabin warm up is not any quicker than the much simpler heating systems in my previous Landcruisers. The seat heater and steering wheel heater and mirror defrost which are all electric do work well though for quick heat up until the climate control heating system can take over.

 

[rgh0]

Pressure tested the coolant system when cold and no leaks. Looking under the car the hoses that are directly under where the leak occurred at -3C to -5C in the snow show no sign of leaks under pressure at 8C at home. Also have been monitoring the whole coolant system and no loss of header tank coolant level and no sign of any leaks under the car in the last week.

Apart from my crazy theory no other ideas

Going back up skiing again in a couple of weeks and I will see if it happens again. I will take some spare coolant just in case .

Photo of coolant lines to rear heater behind LH inside wheel arch

Marked header tank precisely and no change when cold in a week of normal driving

cheers
Rohan

 

[volkswagens-for-life]

I've had many cars drip the smallest amount of coolant when in snow then never again. Probably not an issue