Bobcat 753 Arm Lift Problems
- Thread starter decoursm
- Start date
- Views: 70422
-
- Tags
- bobcat 753
Wew...
So at the advice of a friend who is out of state. I pulled the front pin out of the lift cylinder attachment. This disconnected the cylinder and would allow me to extend the arm fully and do a check to see if fluid was bypassing the piston and/or seals in the left lift cylinder. That was the intent. I started the bobcat and hammered down on the lift peddle and the whole rod shot out of the cylinder and fluid began to pour out of the hole. Oly' goodness! Apparently the rod backed out the nut? However, I can't find the nut inside the cylinder assembly. Again, I haven't pulled the cylinder assembly completely yet. Will do that tonight. Good news is the rod threads look fine on the end of the rod.
Dennis,
he recommended I test the cylinders first before I swapped the load checks...
I was planning on pulling the cylinder apart in the garage and checking the internal components. Also I was going to get caps for the left lift cylinder hyd lines and check to make sure the right lift cylinder is functioning properly.
Thoughts at this point?
I am editing the above posts and attaching pictures of the control valve and lift spool assembly...
Thanks,
Matt
So at the advice of a friend who is out of state. I pulled the front pin out of the lift cylinder attachment. This disconnected the cylinder and would allow me to extend the arm fully and do a check to see if fluid was bypassing the piston and/or seals in the left lift cylinder. That was the intent. I started the bobcat and hammered down on the lift peddle and the whole rod shot out of the cylinder and fluid began to pour out of the hole. Oly' goodness! Apparently the rod backed out the nut? However, I can't find the nut inside the cylinder assembly. Again, I haven't pulled the cylinder assembly completely yet. Will do that tonight. Good news is the rod threads look fine on the end of the rod.
Dennis,
he recommended I test the cylinders first before I swapped the load checks...
I was planning on pulling the cylinder apart in the garage and checking the internal components. Also I was going to get caps for the left lift cylinder hyd lines and check to make sure the right lift cylinder is functioning properly.
Thoughts at this point?
I am editing the above posts and attaching pictures of the control valve and lift spool assembly...
Thanks,
Matt
Attachments
All,
So here is my theory, tell me where I have gone wrong. I pulled the right lift cylinder apart and aside from some scoring on the end cap everything internally looks normalm. My theory here is that since the gland nut came off fluid began bypassing the left gland thru the rod hole. This would mean that the lift system could not build pressure on either side. This is what's causing the bucket arms to fall when up is commanded. When I go to neutral on the lift pedal the bucket stops after a few inches of travel as pressure builds when the spool closes. However, this still doesn't explain the air in the fluid. Thoughts?
The left lift rod end thread is slightly worn as it looks like the rod was meeting metal as it bottom out, most likely on the gland nut. I used the right gland nut to see if I could tighten it on the left rod thread, but the end threads are damaged. So you think I can take it to a machinist and save the rod?
o
So here is my theory, tell me where I have gone wrong. I pulled the right lift cylinder apart and aside from some scoring on the end cap everything internally looks normalm. My theory here is that since the gland nut came off fluid began bypassing the left gland thru the rod hole. This would mean that the lift system could not build pressure on either side. This is what's causing the bucket arms to fall when up is commanded. When I go to neutral on the lift pedal the bucket stops after a few inches of travel as pressure builds when the spool closes. However, this still doesn't explain the air in the fluid. Thoughts?
The left lift rod end thread is slightly worn as it looks like the rod was meeting metal as it bottom out, most likely on the gland nut. I used the right gland nut to see if I could tighten it on the left rod thread, but the end threads are damaged. So you think I can take it to a machinist and save the rod?
o
SSdoxie
Elite Member
Glad you found the lift problem. That rod should be salvageable, clean up end of the threads. I don't see any evidence of Loctite on the rod threads. Red (hi-temp) Loctite is called for in service manual on these threads.
SSdoxie
Elite Member
I don't have any good advice on getting this out. The piston does need to be kept square with the barrel as it comes out so it is sliding only on the seal. Coat hanger likely has too much flex to do this. I would check with a hydraulic shop, sure they have run into this before.
Look inside the barrel for any sign of scratching or galling, it there is the barrel may not be reusable and require a new complete cylinder. Cost of barrel is close to 75% of complete cylinder add in cost of piston, nut, and seal kit it could be more than a complete new cylinder.
Look inside the barrel for any sign of scratching or galling, it there is the barrel may not be reusable and require a new complete cylinder. Cost of barrel is close to 75% of complete cylinder add in cost of piston, nut, and seal kit it could be more than a complete new cylinder.
Dennis,
Have up and dropped of the cylinder at Souther Marland hydraulics. They are attempting to remove, rebuild and reseal. I agree, my local tractor stop stated that the tube may be damaged as we are able to move piston about half way up the tube with compressed air. At about halfway it lodged and would not move further up. I'm hoping it's damaged.
