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Sludge In Oil That Does Not Mix With Oil

Birken Vogt

Charter Member
Joined
Nov 30, 2003
Messages
5,305
Location
Grass Valley, Ca
This morning had one of the most mysterious jobs ever.

It was to be a normal annual service on (air cooled 1.75 qts oil) generator. Arrived to find it had most recently locked itself out with a low oil pressure fault of which the customer was not aware. It had run 200 hours without anybody looking at it so this is not unusual at this point.

Pulled the dipstick and found no oil on stick but a little bit of tar-like substance that took some effort to wipe clean. Added oil with about 50% of system capacity and it showed good enough on the stick to start. This is unusual because normally they have to get a lot lower than that to shut down on LOP.

Engine cranked very slowly at first. Once it warmed up everything seemed normal. Customer did mention that it had been laboring during last major run.

Drained oil and it was pretty black and drained slowly but looked otherwise normal coming out.

The weirdness happened because after setting a while, this black sludge settled out with the oil on top and sludge on the bottom. The sludge resembled fine garden silt in texture. After pouring the oil off the top the sludge remained in the pan and you could draw a finger through it and it would stay clear of the bottom.

After sitting the rest of the day all over the drain pan the rest of the oil had drained away and the sludge resembled chewing gum but not sticky. Peels right off everything. I got some between my fingers and smashed it real thin and washed it in the sink thinking it may have been sugar. But it made no effort to dissolve, it just stuck all over my hands. Reminds me of the thick grease from a Cat that has sat in the woods for 40 years. Or maybe pine tar but not sticky.

Quantity of sludge was roughly 30-40% of drain oil. The longer it sits the more it separates and coagulates.IMG_20201013_170342916.jpg
 

Welder Dave

Senior Member
Joined
Oct 11, 2014
Messages
12,257
Location
Canada
Mixing synthetic with conventional oil or using some kind of additive? Know a guy who had a repair shop and had a Ford gas truck in because it was down on power. Owner used synthetic oil but figured it was OK for 25,000kms. Pulled the valve covers and it looked like shredded rubber inside. Ran engine flush through it 3 times to get rid of all the crap.
 

mitch504

Senior Member
Joined
Feb 27, 2010
Messages
5,776
Location
Andrews SC
I can't see it being related, but, I just rebuilt a planetary wheel hub that had stuff like that in it. It had completely eaten the wheel bearings and lost it's oil. It had this sludge in it, and once it dried, it was hard and crunchy. It had Mystik gear oil in it for 20 years.
 

funwithfuel

Senior Member
Joined
Mar 7, 2017
Messages
5,518
Location
Will county Illinois
Occupation
Mechanic
A while back, we had a Volvo/Penta in a Gradall. It was shutting down due to low oil. We get out there and pull the stick, it was ok. Started it, no oil pressure after 10 seconds. Pulled the drain and nothing comes out. Stuck a screwdriver in the drain and pulled jelly. We pulled the pan and thought for sure we had a bad liner or head gasket. It was 100% gelled up. Let it sit overnight in the warm shop and the bottom 3" or so returned to oil. We thought sabotage after ruling out coolant intrusion. Oil sample said plane ol water was the sole contaminant. I posted pics up here, but I'm not a good search person. Perhaps, maybe, you're getting water in, through somewhere. With only 2 its, it wouldn't take much to compromise the quality.
 

Vetech63

Senior Member
Joined
Aug 10, 2016
Messages
6,362
Location
Oklahoma
There is no telling what kind of oils or additives have been put in that engine. Ive seen a coolant leak into the oil do that like FWF said and more times than not it is 100% gelled up.
 

skata

Senior Member
Joined
May 10, 2007
Messages
1,541
Location
midwest
How often does the generator start up? Could be a moisture buildup issue from repeated starts and not warming up?
 

Birken Vogt

Charter Member
Joined
Nov 30, 2003
Messages
5,305
Location
Grass Valley, Ca
These units do run a frustratingly short (5 min) exercise and they always have milky oil when we change them. But we have changed hundreds of them and never anything like this. Air cooled engine by the way and fuel is natural gas. Also this thing has run several long duration outages very recently and experience has shown that will normally burn the condensation right out of the oil.

I am open to the idea that it is condensation, but skeptical. How could it be that it mixes with oil and then separates out again? Unless the water had some sort of chemical reaction with the oil.
 

MarshallPowerGen

Senior Member
Joined
Nov 26, 2017
Messages
442
Location
Northwestern USA
Occupation
Generator Technician & Equipment Mechanic
Generac I take it (with the 5min excercise time)? Anything strange under the valve covers, or any blockage in the crankcase vent? I take it the "sludge" didn't stick to a magnet?

Had a lot of the coffee creamer jello molds under the valve covers up here, but don't recall anything like you're seeing.
 

Birken Vogt

Charter Member
Joined
Nov 30, 2003
Messages
5,305
Location
Grass Valley, Ca
Did the overhead as part of the job. The oil that pools in the hex socket bolt heads resembled honey but no sludge up there to speak of. I think I know what you mean by Jello mold but that does not happen here, probably not cold enough. All we get is light condensation in the oil when draining, that was definitely not how this appeared, just dark brown or black.

I would suspect sabotage since it is in a downtown location and loud, but it has locks that the customer keeps locked that were not damaged. The key is pretty common though but that is going a little far for a saboteur to sneak into someones completely visible back yard and mess with equipment right outside their house.
 

Truck Shop

Senior Member
Joined
Dec 7, 2015
Messages
16,535
Location
WWW.
Non detergent oil and synthetics don't do well, neighbors pressure washer with Honda engine.
it was low on oil so he dumped some straight 30 wt non detergent in it to pressure wash his house
then didn't use it for 4 months-it looked like tar. Just a guess.

I do know Power Punch and 75x90 turns to goo in wheel ends on trailer axles and is a slime ball
to clean up.
 

Birken Vogt

Charter Member
Joined
Nov 30, 2003
Messages
5,305
Location
Grass Valley, Ca
The longer the globs sit in my drain pan the thicker and stickier they get. I think the oil is draining out of them and they are thickening up. They stick together pretty good but they peel off surfaces in one piece. My wife made brownies yesterday and these things behave like a sticky brownie in a pan. Work them gently and they act like a sticky blob, mash them up and they crumble for a bit. They seem somewhat granular in this condition. Water does not affect them but I put some on the bench with acetone. Acetone slowly dissolves them into brown liquid that thins out and spreads out. More to come, a lab may be in our future.
 

Birken Vogt

Charter Member
Joined
Nov 30, 2003
Messages
5,305
Location
Grass Valley, Ca
Well here is the end to this saga. Had another one today. This time a 4.3 GM engine running propane. The story is a little more clear on the GM, it has been running off and on unattended for years, and neglected. It just flat ran out of oil and was running on a teaspoonful of sludge. Sort of like when you leave a pot of soup on the stove and go away for the weekend. So it turns out you do need to check the oil once in a while and change it every couple of years whether it needs it or not [joke]. Both these units were the factory fill but different engines, different fuels, one air cooled the other water cooled, one 1800 RPM the other 3600 RPM, but same exact result in both cases.
 

shopguy

Senior Member
Joined
Jul 2, 2011
Messages
502
Location
Alabama
An old man told me that during the depression he ran a model T out of oil on the way back from the syrup mill and he poured syrup in .it made it home but of course when it cooled she was done. They got someone with a few tools to take it apart he said it was the best syrup candy he ever ate.
 
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