Mustang 345 lifting slow, but fast while tilting back

[kershey]

This machine has always had a very small hydraulic leak requiring me to add a gallon every fall. Otherwise it has been a solid workhorse. But this lift situation is slowly getting worse and to the point that it moves at 1/4 speed of normal. Unless you heel the tilt pedal, then rockets up ... just like usual. Can anyone suggest where to look first? Everytime I load it up and bring to the shop it's $500. Thanks in advance..

 

[Bobcatdan]

I would say maybe the spool is not moving fully. Something is restricting flow, flow equals speed, pressure equals power. When raising the boom, does is sound like it is laboring?

 

[kershey]

I would say maybe the spool is not moving fully. Something is restricting flow, flow equals speed, pressure equals power. When raising the boom, does is sound like it is laboring?

Thanks for the reply. No it doesn't seem to be laboring. Or at least the motor is not laboring ever. The lift is slower than usual when loaded with dirt or gravel, but when the bucket is empty and you put your heel down on the tilt pedal it flys up like usual. As far as the spool, I don't know what the spool is. I'll google it and see if I can see a picture.

 

[Tazza]

Thanks for the reply. No it doesn't seem to be laboring. Or at least the motor is not laboring ever. The lift is slower than usual when loaded with dirt or gravel, but when the bucket is empty and you put your heel down on the tilt pedal it flys up like usual. As far as the spool, I don't know what the spool is. I'll google it and see if I can see a picture.

As it moves fast without a load, but slow with one makes me lean towards pump wear or a sticky relief valve.
When the pump wears, it can't build up as much pressure as its leaking internally. This is only a real issue when there is a load, when there is little load it has no problem moving X amount of oul at Y pressure. But when there is a load, as it tries to build up pressure due to the load, the flow drops right down from the leakage.
The same can be said about the relief. If there was something stuck in it, it will allow oil to flow back to the tank without being able to build up system pressure.
The best way to test it is to hook up a 3,000 PSI gauge to the aux lines and operate them. See what pressure get vs what is in your manual. I'd suspect th 2,500-3,000 psi range.
The spool is the part in the control block that diverts oil. As you move a pedal, it moves the spool in the control block. Essentially like a tap, move it a little, it moves a little oil etc.

 

[Tazza]

As it moves fast without a load, but slow with one makes me lean towards pump wear or a sticky relief valve.
When the pump wears, it can't build up as much pressure as its leaking internally. This is only a real issue when there is a load, when there is little load it has no problem moving X amount of oul at Y pressure. But when there is a load, as it tries to build up pressure due to the load, the flow drops right down from the leakage.
The same can be said about the relief. If there was something stuck in it, it will allow oil to flow back to the tank without being able to build up system pressure.
The best way to test it is to hook up a 3,000 PSI gauge to the aux lines and operate them. See what pressure get vs what is in your manual. I'd suspect th 2,500-3,000 psi range.
The spool is the part in the control block that diverts oil. As you move a pedal, it moves the spool in the control block. Essentially like a tap, move it a little, it moves a little oil etc.

Sorry, i mis-read, it sounds like its not the pump or relief, but control block. My bad.
If a centering spring in the control block is broken, it could do this. Even an internal crack in the control block. Something sounds like its out of alignment.

 

[kershey]

Sorry, i mis-read, it sounds like its not the pump or relief, but control block. My bad.
If a centering spring in the control block is broken, it could do this. Even an internal crack in the control block. Something sounds like its out of alignment.

Sorry I ddin't reply sooner, had to travel out of state. I was talking with my son and he said it leaks oil when it sits in the barn. I typically look for leaks when I'm operating it. It doesn't seem to leak much if any when using it. My son said it leaks about a cup or so on the barn floor when it sits a few days. I'll try and find the leak and post more info.

 

[kershey]

Sorry I ddin't reply sooner, had to travel out of state. I was talking with my son and he said it leaks oil when it sits in the barn. I typically look for leaks when I'm operating it. It doesn't seem to leak much if any when using it. My son said it leaks about a cup or so on the barn floor when it sits a few days. I'll try and find the leak and post more info.

You were right! The 6" cast aluminum tube that has the valve and spring inside were extremely corroded from manure. Took it off and soaked in engine degreaser overnight and put it back on. It's been work ever since. It does still leak about 1/8 cup everytime we park it overnight, and it only drips a couple drops after my heal comes off the pedal after lifting.