Black spark plug ooze

doug.nichols

doug.nichols

Senior Member
Well, I took "Trudy" on her first road trip since I have owned her. Just 15 miles. She did great. Lots of hills here on Orcas Island, WA, but I never went over 30 mph. When I got home I popped the hood and noticed that some black liquid appeared to be leaking from the number 2 and number 4 plugs. See the two picture attached. Does anyone know what this substance might be and what could cause this?

Also, Trudy sounds like she has a know at modest rpms from time to time. I realize that is not much background on which to base an assessment, but cans someone tell me what would be the most common source of such knock? I have never had the engine apart.

Thanks,
 

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Oil rings may not be sealing good? Tighten up plugs see if loose! and also if plugs have rings (washers)on them!
 
Thanks Gary. The plugs are tight and have rings on them, although I could replace the rings and see if that helps. I fear it might be rings.
 
I was going to say the sealing rings too. What you could try also; wrap the thread with teflon tape and try that. The thread will cut through the tape for grounding. It works for Model T's and they used 1/2" pipe thread. If you replace the sealing rings, try the copper type. They might seal better.
 
Thanks redmodelt. I was just looking on Snyders at copper plug gaskets as I saw your post. Probably worth the small cost to see if it is something simple.
 
Tighten your spark plugs...if that black stuff is oily and she has a knock ole Trudy might be a little banged out, her prom date days are way behind her..
 
Jack:

I was suspecting that Trudy may need some serious engine work as you suggest, but I am not capable of doing that work. So now, I need to decide if a new motor is a simpler and faster solution (and expensive) or whether I should try to find a local mechanic to open her up. I doubt that there are many such folks in my area.
 
New motor???! It's way to premature for that. #1, make sure you aren't running too rich, tighten the GAV until it chuffs a bit on deceleration then open just enough to almost eliminate it, that may be whats causing the carbon/goo around the plugs. Also make sure you are using premium gasoline. Are you sure the knock you're hearing isn't ping? Advance the spark until it pings, then retard JUST enough to eliminate it. When pulling a hill is where you'll hear the ping (knock) the most if you are too advanced, retard a click or so when pulling a hill. However, you need to find the sweet spot by advancing until it pings, then backing off the spark.
 
There are alot of folks around who do engine work. a cheap harbor freight stethoscope can help to pinpoint the knock.Years ago mechanics would do an 'overhaul' ..hone cylinders,fit new piston rings,lap valves, adjust rod and main bearings to restore power.Cant tell whats wrong with your engine over the interwebs..whole lot of guesses and assumptions will come forth,guaranteed.
 
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I had this same problem, and it turned-out to be the piston rings were not sealing properly in my rebuilt engine. I used synthetic oil before the rings seated. After changing the motor oil to SAE 10W30 detergent, non-synthetic for a few hundred miles, the oozing stopped and I returned to a synthetic blend 10W30 (Mobil 1).
By the way, a compression check was normal for a freshly rebuilt engine.
 

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Thanks all. The black ooze seems to have burned off and has not yet returned. I will install new plug gaskets anyway when they arrive. As for the knock, I think I will pull the pan and see what a novice can see.
 
Before you pull the pan make sure that the knock you hear isn't a ping from running too advanced.

Try running the spark lever a little bit at a time less advanced to see if the knock gets less or goes away.

Do you know if the engine has a high compression head? If it does have a high compression head running the spark advance as if it was a standard compression head will almost certainly cause it to ping/knock.

Pulling the pan is a fairly straight forward project but putting it back on correctly to eliminate leaks is a bit more demanding.
 
What are you going to do after pulling the pan? You called yourself a novice, so unless there’s a verified reason to pull the pan, don’t!!! If you’re not schooled in Babbitt bearing and assembly and not realizing the pan is part of the oil seal mechanism, you may be asking for more than you want to deal with, at this point of “model A ing “ not to mention causing more problems.
 
Chuck:

I was considering pulling the pan to see if there is any foreign matter such as babbitt pieces in the oil, and I am curious to see if there is significant sludge buildup that might be inhibiting the oil pump.
 
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