What is this ?

[AVCUPRA290]

Hi,

I took a look underneath my car this afternoon and saw these strange moisture white traces..

What could it be and where can this come from ?

FYI I have a vagsport res delete and to prevent any leaks between the exhausts pipes I’ve used High temperature silicone to make some joints.

Could it be the silicone cracking with temperature and letting some condensation water pass threw the collars ?
Even if this is it why would it turn into moisture ? Before making joints I had water leaking there but it never turned to moisture.

I’m currently experiencing white smoke sometimes at startup and was suspecting the PCV starting to die, but maybe it’s the moisture / excessive water being burn at start up or my current issue helped forming moisture…

if someone has an idea

Here the white smoke

 

[thespicemustflow]

When you say you used 'high temp silicone', what exactly did you use?

I personally don't know of a single exhaust-grade silicone that exists. You need to use exhaust assembly paste, which has a consistency more like toothpaste. Exhausts (admittedly not at that point) can reach 600c and I don't know of any silicone-based product that could withstand that.

Exhausts naturally create moisture in operation due to condensation in the gases - this is is why exhausts quite often rust from the inside out. To me, it looks like whatever stuff you've used is starting to break down, its leaking, and letting its own moisture, along with whatever is inside the exhaust drip out.

As for your video with white smoke, I wouldn't say that's 'smoke', it looks like perfectly normal fresh combustion exhaust on a cold engine.

 

[cuthound]

When you say you used 'high temp silicone', what exactly did you use?

I personally don't know of a single exhaust-grade silicone that exists. You need to use exhaust assembly paste, which has a consistency more like toothpaste. Exhausts (admittedly not at that point) can reach 600c and I don't know of any silicone-based product that could withstand that.

Exhausts naturally create moisture in operation due to condensation in the gases - this is is why exhausts quite often rust from the inside out. To me, it looks like whatever stuff you've used is starting to break down, its leaking, and letting its own moisture, along with whatever is inside the exhaust drip out.

As for your video with white smoke, I wouldn't say that's 'smoke', it looks like perfectly normal fresh combustion exhaust on a cold engine.

I haven't used this on a car exhaust, but have used it to seal the flue on my narrowboat. It is heat resistant to 1200 degrees C. It gives of rather smelly fumes whilst it cures when first heated.

Envirograf Silicone Sealant Heat Resistant Up To 1200 Degrees - Black - £19.00 :

Envirograf Silicone Sealant Heat Resistant Up To 1200 Degrees - Black - Envirograf Silicone Sealant A permanently flexible silicone sealant which is suitable for all high temperature applications such as sealing all single wall flue joints, stove connections and around register plates. Will...

www.glowing-embers.co.uk

 

[thespicemustflow]

I haven't used this on a car exhaust, but have used it to seal the flue on my narrowboat. It is heat resistant to 1200 degrees C. It gives of rather smelly fumes whilst it cures when first heated.

Envirograf Silicone Sealant Heat Resistant Up To 1200 Degrees - Black - £19.00 :

Envirograf Silicone Sealant Heat Resistant Up To 1200 Degrees - Black - Envirograf Silicone Sealant A permanently flexible silicone sealant which is suitable for all high temperature applications such as sealing all single wall flue joints, stove connections and around register plates. Will...

www.glowing-embers.co.uk

Interesting - never heard of such a thing!

I assume it's not that product that's been used though, as this looks black, and the pictures are white. Plus again I'd wonder if it's chemically compatible with exhaust gases/chemicals from petrol engines...

 

[AVCUPRA290]

When you say you used 'high temp silicone', what exactly did you use?

I personally don't know of a single exhaust-grade silicone that exists. You need to use exhaust assembly paste, which has a consistency more like toothpaste. Exhausts (admittedly not at that point) can reach 600c and I don't know of any silicone-based product that could withstand that.

Exhausts naturally create moisture in operation due to condensation in the gases - this is is why exhausts quite often rust from the inside out. To me, it looks like whatever stuff you've used is starting to break down, its leaking, and letting its own moisture, along with whatever is inside the exhaust drip out.

As for your video with white smoke, I wouldn't say that's 'smoke', it looks like perfectly normal fresh combustion exhaust on a cold engine.

Hi,
I used this one precisely indeed and it was originally black silicone :
Became white as it probably cracked and some moisture grew on it.

I was looking for a solution non permanent allowing me to put back my OEM resonator in case I want too.. will the assembly paste allow me to take off the pipes without cutting them ?

The smoke is blueish and thicker than condensation that’s why I was a bit concerned. I’ve also found a small oil pool on the intlet and I have some big vacuum from the crankcase (negative pressure)