M7060 3PT return line blows

[Al38kit]

There is a small hydraulic return line just behind the cab.
It is hooked to a T fitting and then the two lines connect to the hydraulic cylinders that lift the 3 point hitch.

Anyone else have issue with these lines coming off the T fitting?

I wired them on last time and tonight they both blew off when I lifted the big mower.

Ideas?

 

[Russell King]

I assume you are talking about the air vent line shown highlighted below. I assume the cylinders are single acting in the upward direction under pressure and gravity downward. That would mean that no hydraulic fluid should on that side of the cylinder. Therefore, I think you have a leaking seal on one or both of the cylinders that fills that upper side of the cylinder and when you lift the three point hitch it forces the fluid into that relief hose and blows it off the fitting.

 

[Al38kit]

I assume you are talking about the air vent line shown highlighted below. I assume the cylinders are single acting in the upward direction under pressure and gravity downward. That would mean that no hydraulic fluid should on that side of the cylinder. Therefore, I think you have a leaking seal on one or both of the cylinders that fills that upper side of the cylinder and when you lift the three point hitch it forces the fluid into that relief hose and blows it off the fitting.

View attachment 175155

Thank you for the insight as to how this should work.

It explains things very well...I'll check the cylinders individually tomorrow.

That makes good sense as I could not figure out why the return line (which it's not) was made that way.

I'll plan to buy cylinder rebuild kits...anyone know how difficult it is to do these small cylinders?

Thanks again.

 

[North Idaho Wolfman]

Yep @Russell King nailed it.

 

[McMXi]

Thank you for the insight as to how this should work.

It explains things very well...I'll check the cylinders individually tomorrow.

That makes good sense as I could not figure out why the return line (which it's not) was made that way.

I'll plan to buy cylinder rebuild kits...anyone know how difficult it is to do these small cylinders?

Thanks again.

Look at page 7-S27 in the WSM which provides good instructions for rebuilding the lift cylinder. Here's a section view of the lift cylinder and the outlet that connects to the return hose.

So you must have signs of oil in that return hose, right?

 

[Al38kit]

Look at page 7-S27 in the WSM which provides good instructions for rebuilding the lift cylinder. Here's a section view of the lift cylinder and the outlet that connects to the return hose.

So you must have signs of oil in that return hose, right?

 

[Al38kit]

Yes, massive fluid in the return line.
This happened again last night as I was lifting the 10' mower.

Thanks for the information.

 

[TheOldHokie]

Yes, massive fluid in the return line.
This happened again last night as I was lifting the 10' mower.

Thanks for the information.

The lift must leak down pretty quickly then.

Dan

 

[Al38kit]

The lift must leak down pretty quickly then.

Dan

That is correct.
I’ve been chasing some issues with the three-point and hopefully I have found the problem.

IF both of the 3pt cylinders are bypassing and leaking, does anything think there may be problems with the overall hydraulic system pressure?

Is it normal for hydraulic pump to be heard?

Last night I think the sound was the noise of the fluid bypassing the cylinder(s) on the return air line.

I'll get at it today and see if it's one or both of the lift cylinders.

 

[McMXi]

Is it normal for hydraulic pump to be heard?

I only hear the hydraulic pump when turning the steering wheel, but that's when it's loud enough to be heard over the sound of the engine. Perhaps I should be more specific and say that I hear a sound when I turn the steering wheel when moving slowly and it's related to the power steering. I say slowly since the steering wheel is typically turned more when moving slowly, and the rpm are often reduced at those times which in turn makes it easier to hear things. I hope that makes sense.

Your question re hydraulic pressure would depend on the rate at which fluid can escape but I can't imagine your leak is sufficient to change the operating pressure within the hydraulic system. You need resistance to build up hydraulic pressure, just like you need resistance to apply a torque. But without putting a pressure gauge in the system it's all guessing right.