Now this is a new one and I have never seen it before. But then again all my vehicles are 30 years old so here it goes........
I noticed that the exhaust pipes under the truck up to the cat are stained with a flourescent yellow stain by the drian holes in the pipes.
There are also yellow stains under the truck in the snow.
The fluid that drips out is frozen and at first I though an animal had a **** under the truck.
The anti freeze is full and the truck runs fine.
What the ????????

 

Reminds me of a Frank Zappa song.

If you're sure it's not coolant (check it again), a possible cause is condensation "rinsing" some mineral deposits out of the pipe. My biggest concern is the color... never seen yellow. Usually it black, sooty water coming out of the pipes of my vehicles.

 

Sounds like sulfer dioxide to me... as long as you have no anti freeze leaks I bet it is normal

 

All I have ever seen is black sooty drips.
But now I have bright flourescent yellow!
It happens when the truck is warming up for 5 minutes on the driveway. It does not drip after its warm.
Little frozen yelllow stains in the snow.
I wonder if Fred is right and this is just a by product of cold weather fuel additives?

 

Freds right, sounds just like sulfur dioxide.

Any chance you are running a fuel that's rich in sulfur? Smell it - does it smell like "normal" gas?

Are you burning lots of oil and using a "special" oil???

Also, this might be a sign of a bad three-way catalytic converter ... when they go bad, I THINK they produce more sulfur than normal - the "rotten eggs" smell... Hydrogen Sulfide - but I don't think that's bright yellow - Sulfur dioxide is, which means the cat might be bad.

I don't know...

 

When's the last time you turned that beast outa the stall and let him take a natural whiz?

 

Are you using Valero gasoline? If so Valero processess 1/2 it's gasoline from what is considered "sour crude" or high Sulphur content crude oil. Some of the gas stations that markets Valero fuels are, Valero, Diamond Shamrock, Shamrock, Ultramar, and Beacon.

For more info....

http://www.washtimes.com/business/20...4327-7447r.htm

When pumping Valero gasoline, or just driving past a Valero gas station you can defineately smell something different in the air.

 

I crawled under for a closer look. It seems that the yellow stains on the exhaust are on the heat shields.

I know there is no drain at the y-pipe so this stuff isn't coming out of the drains.Very weird indeed.
Anti freeze would not freeze in the snow and this stuff freezes like ice.
My oil was a litre low for some reason so I added a litre.
We have had 2 nasty blizzrdas this last week and maybe this is from snow piling up where it shouldn't be.
Or maybe this is an old fashioned coolant leak? Does the V10 have any coolant leakage problems that are well known?
I started it up and ran it for 5 minutes and no leaks I could see.
Hmmmmmm.

 

Mr Big gettin any snow down your way???????

Thats funny !!
Blower out she's backed up holdin her water!!!!!!!

If you had a coolant leak it would be steam out the pipe ,well up there you'd be making snow at those temps

Just condensation mixed with exhaust by product (Hydro carbon's )

Greenie posion ,so they say
Rich

 

sorry to say this Canadian brother but yes the 99s especially were prone to craping a head gasket or two as they aged ....that said a slight anti freeze leak evaporating the water out of it on it's way down the exhaust system may leave a yellow substance that probably will freeze in your -20 to -35 air... sure hope I am wrong but if this is not combustion water leaking out of the factory weep holes then you are probably screwed

 

Its probably just condensation mixing with surface rust on the pipes dripping into the snow. Or it could be a combination or road grim and chemical deicers dripping off the exhaust.

 

I have notcied that under mine as well. It never leaks a drop, but I occasionally see a yellowy-green substance on the Y Pipe. It was right after the coolant was fushed, so I figured that they spilled a little or something. I haven't seen it in a long while. How long does it take for a head gasket to go? I hope it blows before the warranty is up lol!

 

Yup.
Yellow stuff on the y-pipe.
I wonder why it appears at different places on the exhaust pipe?
Mine is stained at the y-pipe, at both heat sheilds and even up on top of the sheild in one place.
And this is idling in the driveway.
I cannot do headgaskets in this weather. I will drive it till spring if I have to.

 

If the coolant isn't disapearing relax.
But take a look at the heater hoses where they go towards the fire wall those clamps are known to leak
Rich

 

Fred, when you said head gaskets, do you mean into the combustion chamber, or outside and down the back of the motor?

There aren't weap holes in the exhaust pipes leading to the cat, so any liquid you see on the y-pipe is definitely not from INSIDE the motor. It could still be leaking out the back of the heads, but Rich has a great idea - check the heater core hoses...