Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
how often do you remove your prop to clean sludge in the hollow cranck?
- Thread starter flysrv10
- Start date
scsmith
Well Known Member
I seem to recall a recommendation of 500 hrs somewhere in Lycoming literatature, but I can't remember where. I could be imagining it.
I didn't know anything about the sludge at 300 hrs when my prop came off to re-seal it. OMG, I thought. So I read up on it, and I think that is where I came across it.
One of the thoughts I had was, YUK! If there is sludge here, what about elsewhere? I think the unique thing about the crank is the high centrifugal load that probably slings the sludge out rather than keeping it in suspension.
My other thought was, "this is engine oil. The only exposure to lead would be from blow-by during combustion. How is there so much?"
Back in the days of leaded fuel for cars, I used to find similar grey sludge deposited in various parts of the engine. Getting rid of this will be a nice side-benefit when they eliminate lead from our avgas.
I didn't know anything about the sludge at 300 hrs when my prop came off to re-seal it. OMG, I thought. So I read up on it, and I think that is where I came across it.
One of the thoughts I had was, YUK! If there is sludge here, what about elsewhere? I think the unique thing about the crank is the high centrifugal load that probably slings the sludge out rather than keeping it in suspension.
My other thought was, "this is engine oil. The only exposure to lead would be from blow-by during combustion. How is there so much?"
Back in the days of leaded fuel for cars, I used to find similar grey sludge deposited in various parts of the engine. Getting rid of this will be a nice side-benefit when they eliminate lead from our avgas.
Mike S
Senior Curmudgeon
Old Honda motorcycle engines used to have a "can" bolted to the end of the crank, just for this purpose.
Worked quite well, but needed regular service/cleaning.
Imagine what our engines would have in the crank if we did not also have a real oil filter??
Rick_A
Well Known Member
Yep. I guess maybe I'm dating myself calling it a fan belt. I remember having many old cars were the fan belt actually drove a fan.
kkmarshall
Well Known Member
Mike S,
I thought about posting the very same thing about the centrifugal oil filter on
70's era Hondas. I think the crank is doing the exact same job even if it wasn't designed for that purpose. As a side note, I see you have ordered a
S-21. I have wings & tail feathers done on mine,starting on fuselage now.
I thought about posting the very same thing about the centrifugal oil filter on
70's era Hondas. I think the crank is doing the exact same job even if it wasn't designed for that purpose. As a side note, I see you have ordered a
S-21. I have wings & tail feathers done on mine,starting on fuselage now.
Last edited:
Mike S
Senior Curmudgeon
Sent a PM about that.
I am not aware of ANY requirement or written recommendation from the manufacturer for cleaning sludge out of the crankshaft between overhauls.
Please provide a link to the document or written recommendation.
scsmith
Well Known Member
Well, like I said Gary, I might be imagining it. I don't remember specifically WHERE I saw it, only that I came across it while trying to understand the sludge I found when I pulled my prop and had never heard of before (My first c/s prop). It was stated as a recommendation.
If I do come across it again, I will post it.
cajunwings
Well Known Member
Crank sludge
At 500-600 hrs there may be some sludge in the crank bore. Some engines will have a lot. I think that is a reasonable interval to take a look.
Don Broussard
RV9 Rebuild in Progress
57 Pacer
At 500-600 hrs there may be some sludge in the crank bore. Some engines will have a lot. I think that is a reasonable interval to take a look.
Don Broussard
RV9 Rebuild in Progress
57 Pacer
JonJay
Well Known Member
Curious why?
There is NOTHING in the Hartzell Prop Owner's Manual 115N about removing the prop and cleaning the crankshaft.
Please show me where this information is located.
BillL
Well Known Member
Sorry, but this won't help. The war birds, probably dumped gasoline in the oil tank too, to aid in start up, this is probably the reason for cycling the prop, if it was a hydraulic prop and not electric.
Steve, The lead is centrifugally separated and can be very hard. It comes from fuel dilution in the oil from primer start ups, and in the IO after shutdown as the system purges from the heat.
The 60's era Fiats also had the end of crank separators but was much larger diameter - -like the pulley.
I have considered a kidney loop (off airplane) centrifugal oil cleaning system, but it would just be too much trouble to install and remove it every few flights. It could clean all the lead out and reduce particle count down to 2 microns.
cajunwings
Well Known Member
Sludge
Where is there sludge? Or why take a look?
Don?t know what causes it to form, but probably connected to the amount of blowby, how rich you run, how often you fly, the fuel you use and operating oil temp. Oil type may play a part as well but I have no data. I can only say that if I get into a fixed pitch engine with 500 or more hrs run time the crank bore will likely have a layer of sludge coating the bore. Over time combustion causes solid particles to form in the oil and the crank does a good job as a centrifical separator. This sludge is very dense and does not scrape out easily. Rust can form under the sludge layer. I like the 500hr/4 year interval to clean it out and make sure rust is not happening. A rust pit beyond a certain depth will scrap the crank. PID coating certainly helps with rust prevention.
Don Broussard
RV9 Rebuild in Progress
57 Pacer
Where is there sludge? Or why take a look?
Don?t know what causes it to form, but probably connected to the amount of blowby, how rich you run, how often you fly, the fuel you use and operating oil temp. Oil type may play a part as well but I have no data. I can only say that if I get into a fixed pitch engine with 500 or more hrs run time the crank bore will likely have a layer of sludge coating the bore. Over time combustion causes solid particles to form in the oil and the crank does a good job as a centrifical separator. This sludge is very dense and does not scrape out easily. Rust can form under the sludge layer. I like the 500hr/4 year interval to clean it out and make sure rust is not happening. A rust pit beyond a certain depth will scrap the crank. PID coating certainly helps with rust prevention.
Don Broussard
RV9 Rebuild in Progress
57 Pacer
JonJay
Well Known Member
Thanks Don. More on the why at 500 hours since Lycoming doesn't seem to care on PID coated cranks. I only have the experience with my IO360 on the RV, wasn't any sludge to speak of at 500 hours, and my 0320 in the Bucker, which I inspected per the Lyc. AD. It had a lot of sludge, but it also had 2200 hours in operation with no record of it ever being inspected. No corrosion was found. I don't recall if it was PID coated or not. It has since been rebuilt.
FYI...
The AD was not for cleaning sludge, but for checking corrosion pitting on the internal diameter of the crank:
https://yeeles.com/Reference/AD/Lycoming/98-02-08.pdf
https://www.lycoming.com/sites/default/files/Inspection of Crankshaft ID for Corrosion.pdf
Those should be links for the AD (98-02-08) and Service Bulletin 505B referred to in the AD.
A Google search also reveals previous VAF discussions on this issue and they are easily found.
Any federally mandated inspections appear to go away with ?PID? stamped on the crank (Painted Internal Diameter).
The AD was not for cleaning sludge, but for checking corrosion pitting on the internal diameter of the crank:
https://yeeles.com/Reference/AD/Lycoming/98-02-08.pdf
https://www.lycoming.com/sites/default/files/Inspection of Crankshaft ID for Corrosion.pdf
Those should be links for the AD (98-02-08) and Service Bulletin 505B referred to in the AD.
A Google search also reveals previous VAF discussions on this issue and they are easily found.
Any federally mandated inspections appear to go away with ?PID? stamped on the crank (Painted Internal Diameter).
The propeller dome was removed when I replaced the propeller blades on my Yak-55. There was a lot of sludge in the pitch control cylinder/piston area. This is centrifugally thrown outward where the piston seal rides.
The V-530 prop is easily taken apart for cleaning and service so I took pictures and posted them on the monoplane forum. This propeller had been re-sealed due to leaking a couple of years previously, so the sludge builds up fairly quickly.
http://www.monoplaneforum.com/viewtopic.php?f=58&t=192
My son Peter removed the sump on his RV-4 to modify it for a Christen oil system. The bottom of the sump had the same sludge. The bottom of the sump has a waffle pattern in it, perhaps to trap that sludge.
These combined observations were an education for me.
Midlife sludge removal from the sump, crank cavity and prop...I think about it.
The V-530 prop is easily taken apart for cleaning and service so I took pictures and posted them on the monoplane forum. This propeller had been re-sealed due to leaking a couple of years previously, so the sludge builds up fairly quickly.
http://www.monoplaneforum.com/viewtopic.php?f=58&t=192
My son Peter removed the sump on his RV-4 to modify it for a Christen oil system. The bottom of the sump had the same sludge. The bottom of the sump has a waffle pattern in it, perhaps to trap that sludge.
These combined observations were an education for me.
Midlife sludge removal from the sump, crank cavity and prop...I think about it.
jliltd
Well Known Member
Decrappify the Crankshaft
To decrappify the crank after a constant-speed prop is removed lift the tail of the aircraft so there is a downward slope of the crank so the cwap can run out. Get about 4 cans of starting fluid and a long narrow brush or shotgun cleaning rod. Place a bucket under the crank opening to catch the cwap. Squirt starting fluid into the crank to flush it and use the long brush to dislodge the tougher cwap. It is amazing what comes out even with a 200 hour engine.
Jim
To decrappify the crank after a constant-speed prop is removed lift the tail of the aircraft so there is a downward slope of the crank so the cwap can run out. Get about 4 cans of starting fluid and a long narrow brush or shotgun cleaning rod. Place a bucket under the crank opening to catch the cwap. Squirt starting fluid into the crank to flush it and use the long brush to dislodge the tougher cwap. It is amazing what comes out even with a 200 hour engine.
Jim
Thanks for all the replies.
I like this method. Thanks Jim. Will be on my list at annual.
JonJay
Well Known Member
Me too.
I see no reason to pull the prop at 500 hours, certainly not the sump. My 0320 went 2200 hours before the inspection, which involved simply wiping it out with a clean cloth, some solvent, and a stick so I could check for pitting, which wasn?t there. Hollow crank, but fixed pitch.
I have never heard of anyone doing this short of the AD requirement for the purpose of inspection, or during a prop overhaul ?cause it?s already opened up.
I have had my prop off twice in 800 hours, once for a cylinder top, and once for a leaking seal. There was t enough sludge to even contemplate cleaning it out.
Always willing to learn, but not willing to open up perfectly working systems if it isn?t absolutely necessary.
Convince us with some facts. I have found nothing except the one lost aircraft due to corrosion that spurred the AD.
jliltd
Well Known Member
No problem. Sorry for the speech impediment (cwap) but the posting sensor software won't allow the real word.
Starting fluid (ether) is our friend. Works a treat.
rzbill
Well Known Member
I can't. Books are 250 miles from me. Going from memory which must be wrong.
I know I have seen either a recomendation or a requirement because I did the deed and I'll tell you there is no ******** way I would have removed the prop without a formal demand to do so.
I did make an assumption that it must be in the Hartzell manual since earlier posts had claimed no Lycoming requirement. Those are the two books I have. It must be in one or the other.
JonJay
Well Known Member
I have both books in front of me. I can?t find any reference to any kind of crank maintenance or cleaning other than the flange when prop is installed.
There are lots of things that are not published that I do and have learned from others over the years. I am around a lot of airplanes. I just have never heard or seen cleaning the sludge out of the crank, nor, outside if the one aircraft that prompted the AD for corrosion inspection on non-PID cranks, zip.....
Still willing to learn, but thus far, not convinced this needs to be done. I have, and will do it if the prop needs to come off, or if someone can give a compelling reason based on fact, not assumption or urban legend, to do it. Taking apart a perfectly working system has its own risks.
There are lots of things that are not published that I do and have learned from others over the years. I am around a lot of airplanes. I just have never heard or seen cleaning the sludge out of the crank, nor, outside if the one aircraft that prompted the AD for corrosion inspection on non-PID cranks, zip.....
Still willing to learn, but thus far, not convinced this needs to be done. I have, and will do it if the prop needs to come off, or if someone can give a compelling reason based on fact, not assumption or urban legend, to do it. Taking apart a perfectly working system has its own risks.
Old Honda motorcycle engines used to have a "can" bolted to the end of the crank, just for this purpose.
Worked quite well, but needed regular service/cleaning.
Imagine what our engines would have in the crank if we did not also have a real oil filter??
You just dated yourself, Mike!
