Chocolate Colored Exhaust?

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nm9stheham

nm9stheham

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Well here is a new thing to muse about....Chocolate colored soot from my /6's exhaust. Here is a picture that gives a good color rendition on my computer; the exhaust soot on the driveway gravel is a dark cocoa color instead of the usual flat black that it showed before.

This chocolate sooting occurs right after start-up idle for the last 3 days. I have never seen this color in an exhaust. It is worth noting that sooting has not occured for several weeks, ever since I rebuilt the carb and stopped the over-richness.

Recent things that might effect this:
- Changing oil to 5W30 Mobil 1 synthetic the day before from 10W30 Rotella.
- Finally running the car some at 65 mph on the interstate as we get it running better and better.
- Not likely, but I put no-ethanol, mid grade in the tank a few days back instead of no-ethanol regular; same brand of gas (local no-name station chain).

I'll check the plugs today to see if they are oiled or sooted; they ran clean before. I know the valve stem seals are shot (after 52 years .... how dare they fail!) The underside of the breather cap and oil dipstick and drained oil show no signs of the tan foaming that comes with moisture in the crankcase.

Any similar observations from anyone on this? Theories?
 

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Internal exhaust pipe condensation, no problem.
The color would change as you get dialed in and not running so rich like the flat black indicates.

Well, unles it spits that all the time. :)
 
Hmmm OK, well this car has recently had a bout 200-300 mile on it (in the last 2-3 weeks). And the tune (carb/timing) had not been changed in over a month (by me). I just never have made a mental note of anything brownish like this before from an exhaust.

Just checked the plugs and there is a barely noticeable hint of oiling on cylinders 6 & 3, and a very, very mild indication of oiling on #5; it's just slightly shiny/oily on the outer metal body & threads, nowhere else. Nothing that would bother me except that the oil rings are not perfect anymore or the guides are loose; the rings may be sticky as this car had been driven an average of 130 miles per year since 1991. Compressions are (1 to 6) 115-110-120-115-120-115 psi (cold and not being started today before the test) so that seems pretty darned good.

One other variable just struck me and relates to the above 2 comments: it HAS been really humid and rainy here in the last 3 weeks, much moreso than is typical here in July; it has been more like Seattle here lately than the VA mountains in summer. Maybe the extra moisture is cleaning out carbon and effecting the color.
 
It's going to condense in the exhaust system everytime you start it up.
This is one of the reasons it's good to get the motor up to temp if you are going to start it at all.

Unless you have an all stainless exhaust or you will get rusty condensation coming out sometimes.

I wouldn't worry about it unless something else says there might be somthing wrong.
 
Just an update on this: The chocolate color was coming from some serious oil burning past the rings. Upon dissassembly, the oil rings were badly varnished and stuck almost completely. The engine would suddenly eat oil at times and be fine at others times, and the chocolate coloration on the ground under the start-up exhaust would come and go with the oil burning; I just missed the correlation with all the other thigns being fixed at the time.
 
nm9stheham said:
Just an update on this: The chocolate color was coming from some serious oil burning past the rings. Upon dissassembly, the oil rings were badly varnished and stuck almost completely. The engine would suddenly eat oil at times and be fine at others times, and the chocolate coloration on the ground under the start-up exhaust would come and go with the oil burning; I just missed the correlation with all the other thigns being fixed at the time.
Click to expand...

No fair cause you didn't tell us that part up front, did you? :)
 
That's right.... I was seeing if you REEEEALLY knew cars... LOL. Hey, I told you that there was some oil on a few plugs then..... waht else do you need to know? LOLx2

Actually, the oil 'eating' at that time really did not register with me as I was busy doing oil changes every 500 miles or so to try to clean out the sludge/varnish. (Ultimately unsuccessful... waaay too much!) So it was probably eating it and I did not really account for it at that time.

It was when we got it out in the last coupla months on the interstate for short bursts that I could see the sudden oil level changes..... and the cocoa in the exhaust would show up again. Plugs would be clear, then some would be oily, as the rings would not stick and then stick in 1 or a few cylinders. Sometimes oil smoke from the exhaust, then other times not!
 
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