oil pan sludge

[SHIPCHIEF]

I'm no expert, but my son Peter and I have taken a couple of Lycomings apart very recently, and both the old high time engine and the old low time engine had a fair bit of sludge caked in the bottom.
I presume both were run on Aeroshell straight weight oil most or all their lives.
The low time engine was running fine on Peter's RV-4. He just dropped the sump to add an inverted oil system. We don't take this to be a problem, as no metal bits were present.
We just wonder about it, should the sump be dropped and inspected at any interval, any comments from the 'old heads' on effects, like more sludge if you don't run an air filter (many old RV-4s don't) or it's just a fact when running ashless dispersant oil?
Will an oil filter prevent sludge build up in the sump?

[g zero]

Most of what makes up aircraft sludge is lead from the 100LL , notice how it is grey in color as opposed to car sludge .
Tom

[Kyle Boatright]

My O-320 was a runout off of a CAP airplane. The logbooks showed it was flown freqently and got oil changes (aeroshell 15/50 as I recall) every 50 hours or so. It had a quarter inch of sludge in the sump when I tore it down.

That engine was running fine at 2100 hours when they took it off of the airplane.

I don't worry a whole lot about sludge.

[aerhed]

Actually, that is exactly what is intended to happen in an air cool airplane motor using the oils we use. What you are seeing is the reason you don't want to suddenly put a detergent oil in there. Let sleeping dogs lie.

[gasman]

It should not be a problem if left there till OH. But you could drop in a couple of quarts of something that will cut float it out the drain plug after it has soaked.

I would then flush with a quart of any oil to remove the solvent residue.

I do agree with post #7...... Do not do this..... I did not consider the inside texture of the pan!!!

[David Z]

When I had my truck engine apart, the oil pan hand some sludge in the bottom. It had 165,000 miles at that point. I always change the oil between 3000 and 5000 miles depending on conditions.

[aerhed]

It should not be a problem if left there till OH. But you could drop in a couple of quarts of something that will cut float it out the drain plug after it has soaked.

DO NOT do anything like this. Leave the sludge where it belongs. There are actually recesses and cavities in the case especially to hold sludge. Breaking up the sludge in an engine already in service is a good way to spin bearings and introduce you to a new landing spot you never dreamed you'd use.