Technical An unsightly discharge

I have been getting this black discharge from my exhaust.
It appears to be waterborne, it's not coolant.
I am assuming that I am getting some water condensation in the exhaust ( flathead with wrapped headers) after I shut it down, and then on start up it gets blown out.
Couple questions:
Is this fairly normal?
And
Would a strategically placed weep hole in the exhaust stop it from happening?
Thanks for the input.
Chappy

 

A little bit of carbon in the tubes, add a little condensation and you get a little spittle out the tailpipes. I used to back my 442 into the garage cause it look cool but now I get to re-paint the back wall of the garage because those flared pipe exits in my rear bumper are like 2 blunderbuss and they "painted" spittle all over the wall.

 

Just condensation. HRP

 

My daily has a small hole on the back face of the muffler, just below the outlet. Possibly just for that reason.

 

I have had several old Ford cars with flat head engines and all of them , after sitting, they all would build up carbon in the exhaust and a little condensation and then out the tail pipes the black stuff would come! It just seemed normal to me.

 

It's not just condensation. The internal combustion process creates moisture as the pistons squeeze the molecules of air and fuel some moisture escapes. Most gets burned off, but some exits with the exhaust picking up carbon on the way. Yes, a weep hole in the muffler(s) should help if there isn't one and it might even prolong the life of said muffler.

 

It is condensation that happens during the first few moments AFTER you start the engine, not after you shut it down. The moisture in the warm exhaust gas condenses on the cool exhaust pipes, picks up some black carbon, and gets blown out the pipes. You know, just like moisture in the warm air of the shop condenses on your cold beer can.

Just another reason those of us in the colder winter climates shouldn't start your car and let it run for a few minutes every week, or whatever interval you think they need to be run. All you end up with is water sitting in the exhaust system, and maybe also in the engine if you don't warm it completely. Better to properly prepare them for winter storage and just leave them sit until hot rod season returns.

 

This IS one of the worst thread titles.
Flashbacks to trips to the health department in the 70s...…..
For you youngsters, shit couldn't kill you back then.. You might wish you were dead, though.

 

Yep, it looks like two shotgun blasts inside my shop door where the son's pickup spewed with the door shut.

 

Just wait till your mother is in her pure white work uniform and you're giving her a lift to work. As she walks past the rear of the car you give it a rev to impress her with the cool sounding exhaust note. Happened 45 years ago and I still get reminded of it.

 

An interesting title, but here I am! Spittle, snot, pretty much the same. Maybe tears of joy, my human still Loves me!

 

Great title. I was here for HAMB S.T.D. advice.

"Rub it with brake fluid. Burn it with gasoline. Run a wire gun brush thru it."

Just say no.

 

I have a pair of Ford Crown Vic cop car mufflers on my heap, courtesy of my mechanic for the county pal. They have little holes in the bottom. Exhaust actually came out of those holes, seemed odd, so I put sheet metal screws in. Guess I'll take them out..

 

Weep holes.

 

That's a really neat explanation

But seriously, when you burn a hydrocarbon (a molecule composed of Hydrogen and Carbon), you get several combustion products, as the hydrocarbon is split up and combined with the air (mostly Nitrogen N2 with some Oxygen O2) molecules. The main products are N2, CO2 (carbon dioxide) and H2O (water), with small amounts of CO, unburned HC, and NOx, along with some other stuff.

So the source of the "condensation" is actually the burning of gasoline in air, to form water, and while the exhaust system is still cold, this water (which is steam as it exits the engine) will turn into water drops.

The black stuff is that HC that made it through with out burning completely. Think of it as charcoal powder.

So yeah, it's all perfectly normal.

 

Calling doctor squirrel...

Doctor squirrel, please come to the emergency room...

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All that fancy science talk has my head spinning and I would never doubt the veracity of my betters, namely Ebb, Don and Jim, so no argument here.
I'd just like to add that the H2O, whether from the exhaust flow or from the ambient atmosphere, is in suspension, in its gaseous state, not yet in a liquid state, so it won't puddle or splatter when the car is running at warmed up temp. It's only when the engine is off and all is still that the imbalance of the cooler temps outside the exhaust chilling the metal versus the warmer temps inside the pipe to trigger the change to a liquid state. Also when this happens, as the gaseous water is spent condensing in the pipe(s), more humidity can be drawn in from the ambient humidity present outside the pipe and add to the liquid crud stockpile. This is why you get greater amounts of black splatter on high humidity days and locations of the country. (I agree with Ebb, too.)
The only cure is a comfortably heated or hermetically sealed garage.

 

I park my cars in a comfortable temperature garage, and they sputter black liquid stuff.

Burning gasoline makes steam (water vapor) and carbon dioxide. The water vapor hits the cold exhaust system, and condenses. It has nothing to do with water vapor in the atmosphere.

 

Well since we're getting all sciency here, water vapour is indeed in its gaseous state. However it is not in suspension. I suppose fog would be an example of water in suspension.

 

Dr is needed......and a shot cleared mine up

 

@williebill no joke. I could share a story about a doctor I went to who's daughter was, uhh, the source of my issue. Back then it wasn't unusual for the healthcare community to ask who you may have had "contact" with in order to keep the spread of stuff to a minimum.

I didn't know her father was a doctor.....

 

AND it's not removable from skin. Was working underneath my OT cobrajet and close to my knee whacked the somewhat ragged edged exhaust outlet. I didn't think anything about it until I went inside later to clean up. After my shower noticed the approx 1 inch long cut/scrape near my knee was BLACK like a tattoo.

It's now 50 years later and faded just a bit but still noticeable, have had a few ladies ask me why I had a black stripe tattooed on my leg

 

Ebbsspeed and loudbang...
Laughing so hard.
Hahaha hahaha
Shit... LOL

Everybody have a good Sunday.


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As usual Jim has a great explanation. I was typing something up when he posted, couldn’t have said it better myself.


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All the old cars do it. A little choke, a little cooler day, add some gas and spark and she starts "getting wet and ready" I don't care how well tuned the car is, but minus things like light off cats and full on catalytic convertors you get the true old school effects. The only danger of this if we wanna call it that is if you make a habit of brief cool condition short run times. The moisture coupled with the acids and soot from combustion will rot all but stainless systems. Best to run long enough to heat up the exhaust system and let the water evaporate after a shut down, and even with a stainless gig because otherwise she pukes it out and makes a mess. Depending on the conditions you might need up to 10 min run time. I could use at least that long this time of year in the Motor State.

 

RE: all the old cars do it. My 8BA never left "deposits" on the drive, but had soot on the exhaust extensions untill it started using more oil than normal. Passenger side was the worst, so pulled the head & found it was time for the high buck rebuild. $$$$$

 

I have a friend who is convinced that it is caused by coolant leaks.
I should tell him that penicillin will clear it right up.

 

If there's antifreeze in the cooling system, you'll generally see white smoke from the tailpipe.

Cold weather makes the steam more obvious, too.

But there is still the very basic fact that water vapor is what you get when you burn gasoline.

 

^ditto

 

As explained earlier, water is a byproduct of combusting fossil fuels. New cars with more efficient engines spit a lot more water out of the exhaust on initial start up, it’s clean though. I have 2 black spots on my driveway where I started my ‘36 with a 350 in it yesterday.

watch the water pour out of the tailpipe of this F-150 about 5:40 in the video