bobcat 743 makes noise when trying to move

Peter M · Jun 8, 2023

I just rebuilt my lift and tilt cylinders on my 743. When I was done my skid steer started making a terrible noise when I tried to move it. lift arms and tilt are working fine. It rolls down hill fine. Unfortunately down hill is now where it is. It makes a awful noise when I try to move it. sometimes moving the levers does nothing other times the levers fight me as I try to move them and the noise gets louder. some times the right side will drive a little then the left drives a little. But no way it is going to go back up the hill into the garage. I figure it is air in the drive and It should work itself out but after 10 minutes of terrible noise I gave up. Not sure what is going on. It did not have problems before I rebuilt the cylinders. Help.

laurencen · Jun 9, 2023

have you checked the oil level?

Peter M · Jun 9, 2023

oil level is fine, maybe a quart over full now.

brdgbldr · Jun 9, 2023

Peter M said:
I just rebuilt my lift and tilt cylinders on my 743. When I was done my skid steer started making a terrible noise when I tried to move it. lift arms and tilt are working fine. It rolls down hill fine. Unfortunately down hill is now where it is. It makes a awful noise when I try to move it. sometimes moving the levers does nothing other times the levers fight me as I try to move them and the noise gets louder. some times the right side will drive a little then the left drives a little. But no way it is going to go back up the hill into the garage. I figure it is air in the drive and It should work itself out but after 10 minutes of terrible noise I gave up. Not sure what is going on. It did not have problems before I rebuilt the cylinders. Help.

It can take a while for all of the air to work out of the system.

Run the machine for a few minutes and look to see if the fluid has foamed up. If it has you have air in the system. If it got to your motors after changing the lift and tilt cylinders it probably means that you foamed up the fluid while driving it and sucked air into the motors.

Run the machine for a little without using the lift, tilt or drive. Check for foam. Once the foam is gone refill the tank. Do this until no foam. Repeat but use the lift and tilt slowly and start with just small movements. Check for foam, refill, repeat. Once you can lift and tilt fully, without any foam, then you can try the drive motors again.

You can try to purge the drive motors by leaving the brake on and just slightly engaging one motor at a time both forward and reverse. This will open the bypass valve an hopefully push the air out.

laurencen · Jun 9, 2023

if its got air mixed in the oil to the stage its foam it takes several days to settle, when it does air is aeverwhere so I would only have motor at idle and as said previously small movements and slow, had this in a bucket truck many years ago and was quicker to drain the oil and refil the tank

Peter M · Jun 9, 2023

I lifted each side off the ground and ran the wheels forward and reverse. Right side first then the left side. and repeated 2 more times for 5 minutes a side. Wheels spin fine. lifted the arms up and down half a dozen times and then the tilt the same. Set it down on the ground and it refuses to go up an incline. its now starting to whine all the time. so now it whines and squeals when it tries to move. sure rolls down the hill nice. At this point I have been fighting it so much to get it up the hill that I may have done real damage to something. Oil has some small air bubbles in it which dissipate in 5 minutes. ( looking through the site glass)

cdmccul · Jun 10, 2023

You may have cavitated the pump at this point... I hope not! But when you say it rings down hill just fine, you mean under some engine power, or with the engine not running at all?