Rebuilding / Cleaning lift tilt dump control advice please

[woodlandfarms]

So I am having a serious leakdown issue on the PT. Worse than normal. I also feel like my lifting capabilities are off by at least 30%.

This all said, does someone have directions to cleaning out the Lift Tilt Circuit? anyone have alink to a tear down video?

As a side note, wanted to gauge peoples interest in the following...

When I took my cylinder to the repair shop, the main tech said that the design was flawed. That the plunger should have another ring (it was either a whiper or an wear ring, can't remember) He said the design was old school and tended to fail quickly. I rebuild my steering cylinders every couple of years so I am thinking maybe it is time to have this shop machine me up some new plungers. Would anyone be interested in this (group buy?)

Not sure if this would apply to the 425 owners but I can get dimensions, It would probably be for the 1430 and 1850 crowd.

 

[ponytug]

If you are talking about excessive leakdown of the FEL, this is what I did. Your symptoms matched mine for the lift part of the FEL. You can trace the hydraulic lines back to the joystick valve block, so you know which check valve to open.

When I cleaned mine, I went in under the loader arms to get to the front side of the joystick valve block. (Prop the FEL up on something solid!) Just below each pair of hoses is a small cover that unscrews the check valve us underneath. Terry warned me that it is a very high precision area and to get the valve assembly and the area around it super clean before unscrewing the cover. As soon as it is opened, it will leak oil, and of course the relevant cylinder will drop!

When mine was acting up, and I disassembled it, I never saw the offending particle of dirt in the ounce or so of oil that came out, but afterwards it worked perfectly. YMMV...

All the best,

Peter

 

[m5040]

If cleaning the valve doesn't work, you could try a stethoscope (or if you don't have one of those, hold the handle of a long screw driver to your ear, and hold the other end on the part you want to listen to, the noise travels through the screw driver and allows you to hear precise areas) to listen for oil bypassing the cylinder packings. If two cylinders are involved, and if one is bad, you would hear a hiss from the leaking area.
Sounds funny but it works.

 

[woodlandfarms]

Hey peter. Are these the bolts you are referring to?

 

[ponytug]

Those are the ones! As you can see, not the easiest place to get super clean.

I have been trying to remember, but I am suffering from a bad case of CRS at the moment. I think that there is a small piece just behind the hexagonal cap, so be prepared for it to pop out just in case.

All the best,

Peter

Hey peter. Are these the bolts you are referring to? View attachment 659585

 

[m5040]

I wonder where the engineered leakdown on the PT hydraulic systems is? Maybe under those caps....

 

[woodlandfarms]

I think it is a combination of this mediocre valve and the cylinders being sub par in design. Problem is I don’t know of a higher quality valve block that will fit in this space and as for the cylinders I am working with the local hydro shop to see if we can improve the plungers themselves.

 

[agjones]

My 425 valve started leaking, redid the seals w pt kit. Still leaking.

Swapping to a 3 spool valve from hydraulic-master.com. Sending the pt in for service.

I've used other valves from hydraulic-master.com, located in Poland, great service and support, seems to hold up well.

 

[ponytug]

Yes, under the little cap is a plastic gizmo that allows a leak down bypass to act as a pressure relief in the cylinder circuits when they are not active.

It would be easy to blame the leak down on low quality.

FWIW: according to Terry, it is an engineering choice. If you do not have a leak, or bypass, then you get pressure spikes in the closed hydraulic circuits when the temperature changes. (With the valve closed, you have oil sealed in a fixed volume container of the cylinder and hoses. If the metal contracts, it raises the pressure in the oil, and vice versa.) That would necessitate higher pressure hydraulic hoses and pistons, and /or having accumulators or relief valves on each circuit.

Terry told me that there are versions of the valve block that do not bypass, but the risk is blowing cylinder seals, and sucking water and dirt past the seals. Given the dirty environment that our PTs operate in, it seemed to me like a reasonable trade off, but what do I know?

I do not know how CAT, Volvo, and the other large equipment makers solve the issue. Could it be that the volume of the circuits in larger machines are so much larger that the temperature effect is negligible?

All the best,

Peter

 

[ponytug]

Just to clarify, did you do the seals in the cylinder, or the valve block?

Thanks!

All the best,

Peter

My 425 valve started leaking, redid the seals w pt kit. Still leaking.

Swapping to a 3 spool valve from hydraulic-master.com. Sending the pt in for service.

I've used other valves from hydraulic-master.com, located in Poland, great service and support, seems to hold up well.