Bucket tilt ok up/down not so much

[mike11]

Im starting to wonder if its in one of these 2 areas, lift/tilt lock or boom man release.

 

[mike11]

Changed the filters
Same symptom goes up 2-3x and gets lazy
Down press is strong if I tilt the bucket all the way straight down and force it down it has tons of pressure

 

[ward]

I dont remember a skid steers having a float postion, I only worked on the new hollands and Gehls and John Deeres, and we also had some toyotas skid steers which got replced by the gehls while working for the rental company 15 years before that I worked construction and we had a mustang it also did not have a float, back in 86/87 I ran a 753 Bob Cat for 2 years and it did not have a float postion.
When you did the leak test was the unit warmed up at operating temperature, as for the spools it should not make a difference in their oriantion, the key is no binding on the linkage when acuating them.
When assemblying them before the springs were put on they should have mooved very smoothly when lubed through bore, as the tolarence between the spoool and valve body bore is such that the high pressure is kept in the valve by the oil film between the spool and valve body the seal is just to keep dirt out and wipe the slight oil film off as the spool is pushed or pullled out of the body.
Did you say you were putting in a new relief valve?
One thing to remember is that a relief valve seat can wear out and will work fine when cold due to the oil being thick but after the oil warms up it can start to open up like it is hydroplaning, think of a fence keeps a critter in until they get their nose under it then they keep pushing until they get past it, as a rule unless noted per manufacturer all test should be done with the oil at operating temperatures.

 

[ward]

I googled the Bob cat 853 and it does have a float postion, if the linkage is not set correctly you may not have enough travel in the peddel to get the valve to the float postion, I did see that there is a place in the manual to adjust the linkage and you may need to review that to make sure it is adjusted correctly.

 

[mike11]

I dont remember a skid steers having a float postion, I only worked on the new hollands and Gehls and John Deeres, and we also had some toyotas skid steers which got replced by the gehls while working for the rental company 15 years before that I worked construction and we had a mustang it also did not have a float, back in 86/87 I ran a 753 Bob Cat for 2 years and it did not have a float postion.
When you did the leak test was the unit warmed up at operating temperature, as for the spools it should not make a difference in their oriantion, the key is no binding on the linkage when acuating them.
When assemblying them before the springs were put on they should have mooved very smoothly when lubed through bore, as the tolarence between the spoool and valve body bore is such that the high pressure is kept in the valve by the oil film between the spool and valve body the seal is just to keep dirt out and wipe the slight oil film off as the spool is pushed or pullled out of the body.
Did you say you were putting in a new relief valve?
One thing to remember is that a relief valve seat can wear out and will work fine when cold due to the oil being thick but after the oil warms up it can start to open up like it is hydroplaning, think of a fence keeps a critter in until they get their nose under it then they keep pushing until they get past it, as a rule unless noted per manufacturer all test should be done with the oil at operating temperatures.

I do have a lift pres relief coming, should be here mon/tues.....even with leaking on 1 cyl i would think it should still go up, so the PR would make sense

 

[FJRDarksider]

My 853 has a float position. Works really well. When I replaced the seals I disassembled the float mechanism (although it operated fine prior) and installed new ball bearings under the cap. Old bearings had a flat spot as the grease was gone so they became fixed in place essentially. Either way, that function I don't think would cause your symptoms. Frustrating for sure though.

 

[mike11]

Changed the lift PR valve, still doing the same thing
What I did notice tonight having it out in snow is it is bleeding somewhere, it leaves little puddles when it sits running, that I’m going to have to track down and find the source of. I believe that could be a major contributing factor. I’m also going to rebuild the lift cylinders in the next few days I will keep you guys posted

 

[mike11]

Changed the lift PR valve, still doing the same thing
What I did notice tonight having it out in snow is it is bleeding somewhere, it leaves little puddles when it sits running, that I’m going to have to track down and find the source of. I believe that could be a major contributing factor. I’m also going to rebuild the lift cylinders in the next few days I will keep you guys posted

Another thing I noticed is after it sits a lil while it’ll work again for a few cycles then get lazy. This leads me to believe and am totally convinced the oil is getting airated, when the bubbles dissipate out of the oil after sitting it’ll be ok again for a few cycles till it gets foamy/bubbly again. Now the challenge is to find out where it’s coming from. I do know the left lift cylinder is leaking internally. Could that fluid rushing past the least at high pressure be enough to cause it to cavitate ?? Maybe maybe not…. Is the external leak allowing air to be introduced into the system ?? Maybe maybe not…. Gonna have to dig and find out. It’s so cold here it’s making doing anything miserable. I need to turn the heat on in my garage almost a day early to be able to do anything.

 

[ward]

Air has to already to be in the cylinder for that to cause it, I had a john deere 240 that waould come in and get refilled with hydrualic oil it had come in several times the guys said it had a hole in the hydrualic tank, finaly I checked it in one day and I checked the supply line to the pump and found it lose right at the lift pump, where it could suck airpast the fitting I took the line off and replaced the "O" ring and tighten it back up and we marked it down to keep an eye on it we found that solved the problem, I don't know if you have a similar issue only way to know is to check from the tank to the pump and wash/wipe the line dry and see if it is leaking, the john deere would be wet at the pump however not overly so like it was flooded persay.

 

[brdgbldr]

A non pressurized line between the hydraulic tank and pump can suck in air, (like trying to drink something through a straw that has a third hole in the side of it). That same line may not leak out any oil because it has no pressure to push the oil out depending on how high up on the line the hole is.

 

[mike11]

A non pressurized line between the hydraulic tank and pump can suck in air, (like trying to drink something through a straw that has a third hole in the side of it). That same line may not leak out any oil because it has no pressure to push the oil out depending on how high up on the line the hole is.

i have encountered that in the past on things, depending on where and how its compromised it can be a pita to find...... as soon as it gets above zero here next week im going to put alot of time in to it and get this wrapped up. I will keep you guys posted. Plan for next week is lift cyl seals, steering pintle shaft seals, and go over every other sq inch of the returns and see if i can find any other areas of intrusion.

 

[mike11]

I dug into it today, found one of the return lines to the T a lil loose, loose enough I could easily move it on the fitting, I’m pretty sure that’s my issue, I ordered new ones, they’re pretty stiff and hard, I’m going to change them and the we steering shaft seals when they come next week and let you guys know. But pretty sure we have this under control now

 

[ward]

if your getting air in the system I am reallly going to bet that it is being introduced by the suction line from the tank to the pump, the return line will be your most likely source where you are getting build up of fluid leaking underneath, a suction line may only show a few drops of oil externally on the line or joint yet allow a lot of air in as air flows easier then fluid.

 

[mike11]

if your getting air in the system I am reallly going to bet that it is being introduced by the suction line from the tank to the pump, the return line will be your most likely source where you are getting build up of fluid leaking underneath, a suction line may only show a few drops of oil externally on the line or joint yet allow a lot of air in as air flows easier then fluid.

Ward the loose one was a return going to the T with the feed from the tank, deff a hi auction line, I’m changing all the lines bobcat stocks and has yet. I’m certain this will fix this issue. It now makes perfect sense, every cycle of the bucket let more air in, after 2-3 cycles the oil was foamed up enough to not be able to build pressure anymore, after it’d sit 15-20 min the bubbles would dissipate out of the oil and it would work again for a few cycles.

 

[FJRDarksider]

That certainly sounds like the cause. Did it function ok after tightening the fittings? or have you left it to replaces lines etc.?

 

[mike11]

It’s apart yet, I’m waiting on new lines and steering spool seals to get here, with the system drained I’m going to change all and anything needed.

 

[mike11]

Replaced the suction hoses, steering spool seals, main pres line to the control valve. Filled it with fluid, attached the bucket. Ran it up and down a few times and did the same thing. Now I did notice if you let it sit a few min it starts to come back like the oil is airated, I do know the left lift cyl is internally leaking. Would that internal leak cause enough cavitation to foam up the oil ??? I can’t see down in the tank. Looks fine on the stick. Could it still have air in it ?? It’s no longer leaving blood stains outside where it ran. I guess I’m down to 2 things.
1 lift cyl seals
2 pump
Nothing else is left. Unless you guys have any ideas. This is really frustrating

 

[ward]

I have never know of a system that had a cylinder bypassing/ internal leaking to cause any problem other then leaking down, if it was causing the problem I would thing it would really drift down fast.
The pump I would think moves oil as soon as the enginge is started to rule out that you have all the issues corrected with the suction lines I would start the unit and run it 3/4 to full throttel ( after letting the engine warm up ) for 5 minutes with out raising the boom then raise the boom and see if the issue comes in sooner then before also have your pressure gauge ready to check pressure at that time that it fails and see what pressure you have.

 

[Jimsteinbrenner]

Replaced the suction hoses, steering spool seals, main pres line to the control valve. Filled it with fluid, attached the bucket. Ran it up and down a few times and did the same thing. Now I did notice if you let it sit a few min it starts to come back like the oil is airated, I do know the left lift cyl is internally leaking. Would that internal leak cause enough cavitation to foam up the oil ??? I can’t see down in the tank. Looks fine on the stick. Could it still have air in it ?? It’s no longer leaving blood stains outside where it ran. I guess I’m down to 2 things.
1 lift cyl seals
2 pump
Nothing else is left. Unless you guys have any ideas. This is really frustrating

Hey Mike. Ive been following along your adventure here. Seems like you should update your profile pic, you probably pulled out the rest of that hair. lol. I'm not positive if your problem was similar to mine but heres my 2 cents. Any way I Have a 610 and had what i think people told me was Hydraulic blow by.( internal leaking in my lift cylinder) I had a huge drop in lift /tilt power after warm up too. After we I blew the main end seal I had too go ahead and rebuilt it. I could tell the interior seals were not holding internal pressure on inspecting it. after the rebuild i hold pressure now all day. My tilt is dropping a little on a long ride so its next. Anyway the seals were very cheap, actually the ones I ordered from Bobcat didnt fit , my buddy ordered a set from amazon for half the price and they were the right ones. Good luck , Jim

 

[ward]

If you have the seals to rebuild the leaking cylinder I would go ahead and rebuild it, just a note though it maybe easier to break the gland lose while the cylinder is on the machine, as a rule all you need is about 1/4 turn to loosen it up and if you dont have a spanner wrench the last one I bought was about $50.00 I dont know what they go for today if you get one like Bob Cat shows it comes with several different size pins I bought my large one through NAPA then I got a smaller one through Mac tools or Macto I don't rermember which they were OTC brand.