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Topic-icon Brushes on Hot Prop making a mess

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1 week 2 days ago #2659

Good morning;
Just about the only thing I can think of re: the gummy brushes is residual oil in the brush holder. It seems you've tried everything else. Remove the brushes and thoroughly clean the brush holder.
As far as the EGTs rising as you reduce power, this seems to indicate a leak in the induction system which would admit non metered air into the induction system. This would lean the mixture since the fuel flow hasn't changed. Leaner mixtures result in higher EGTs.
I know it's a new engine but I would thoroughly inspect the induction system
Let me know what you find.
Steve

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  • james Long
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1 week 5 days ago #2658

Sorry for the delay in reaching back out to you. New computer and I just found this in my "Junk". Earlier this week I took it back to my shop to inspect and show where it was still making grime on the brushes and enough to throw it on the front of the cowling. Here are some things you should know.
- This was a reman engine from Continental installed 5/20
- Maxwell rebuilt the prop
- Even though we knew it would not make a difference we swapped the brushes Lt to Rt. Still same result.
- I took it back in the shop earlier this week to show the results.

Everything on the front of the engine is extremely clean. I will let them know about your comments. If you have any other ideal please let me know.

Also I have another issue. New engine issue. When I am pulling back the power for pattern set up, at the current mixture I watch the old engine's EGT get cold (as I alway have seen) but the new engine get high EGT. On experiment I would then full rich new engine and then it would come to normal operation but not cold while the old engine would stay cold without touching the mixture. (BTW I base I would full rich as part of my GUMP). They have set up the high/low pressure a few times and to no avail. Ideas?

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3 weeks 4 days ago #2627

Hi James;
I checked with Todd, the prop guy at American Propeller and he told me that there's oil, probably from the engine crankshaft prop seal, but it could be from another spot since, hard as it may be to believe airflow in the engine cowling does swirl despite the speed of the airplane. Todd said that the oil will bond with dirt and dust to turn into an abrasive mixture that will quickly wear the copper band on the slip ring. Cleaning the brushes and brush area with contact cleaner or electrical cleaner should be done before flight to make sure that the slip ring is not worn excessively by the abrasive oil/dust/dirt combo.
Steve

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  • james Long
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4 weeks 16 hours ago #2620

We have changed the brushes from LT to RT, per my request. This to confirm it is not the brushes. The tech has looked at the prop multi times and he said it is clean every time. that is why I had them switch the brushes. I will be looking at the cowlings in the near future until the grease comes back. Will keep you posted and thanks as always.

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4 weeks 1 day ago #2618

Hi,
My troubleshooting brain, plus the TS ing you've already done leads me suspect that you have a oil leak past the crankshaft seal. Nothing else accounts for this. You've changed brushes, and it only happens on one side so, it has to be something else. The sources of oil up there are the crankshaft oil seal, or the prop.
Are you seeing any evidence of oil leakage from the prop.
One simple oil leakage detection method is to clean the front of the engine around the crankshaft as well as possible. Then spray dye leak check detection spray--it's a white powder--over the area. Fly the airplane and then check for the presence of oil in the area covered by the white spray.
FWIW, I've heard that spray athlete's foot powder also works.
I have reached out to my favorite prop shop for ideas. If they have any suggestions, I'll post them.
Please keep me abreast of what you're doing and what you find so I can pass it on if this comes up again.
Steve

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1 month 2 days ago #2613

I have a PA34-220T. (Seneca III) and one of the hot prop brushes was worn out and was replaced 10 months ago. After a new brush was installed it started making some sort of goop around the brush and then throwing it onto the front cowling. It was cleaned and checked 3 times and all looked good including the adjustment. My tech then replace the bottom brush. Same thing happened. We then replaced both again and adjusted. Same issue. Last week they called Maxwell and sent pictures and they replied they have not seen this before. They have been in contact with our local rebuilding engine shop (Bolduc Aviation) and they have not seen or heard of that also. After months of going through this i believe it is happening while going through rain. the other engine does not have any issues. It has been cleaned and adjusted many times and the new brushes, with now about 150 hours on it still look new. See pictures below.


Any help would be greatly appreciated.

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