How to Determine Spool Orientation in Hydraulic Valve (Rebuilding Main Control Valve)

[Howey Matt]

I'm rebuilding the main control valve in my Cat 304CR (NAD00987) and I'm having trouble determining which way to install the spools. Some of the spools look like they're the same on each end -- others are clearly meant to be installed in a particular orientation. All of the spools have a groove/ring on one end (see photo). I'm wondering if this ring is used to determine the orientation.



The service manual doesn't make it clear which way the spools are installed, and in some places, it contradicts the parts manual. For $500+ I had hoped it would be more useful. There is this hydraulic schematic (see photo). Is there any way to tell which way to install the spool from the schematic?

 

[Nige]

For something like an MCV the Service Manual is designed to be used in conjunction with the Parts Manual which has much more detail including sectional views. Taking photos during disassembly, and probably only disassembling one section at a time, is advisable.
Attached Parts detail of the MCV and the various sections. Best I can do, sorry in advance if it's not what you are looking for.

 

[Howey Matt]

For something like an MCV the Service Manual is designed to be used in conjunction with the Parts Manual which has much more detail including sectional views. Taking photos during disassembly, and probably only disassembling one section at a time, is advisable.
Attached Parts detail of the MCV and the various sections. Best I can do, sorry in advance if it's not what you are looking for.

Are you able to tell which way to install the spool from the parts manual diagrams? I can't tell. I thought the parts manual diagram for the Boom I valve showed the spool being installed one way, and the photo in the service manual shows it the opposite way.

 

[Nige]

Are you able to tell which way to install the spool from the parts manual diagrams?

I would have paint-marked them as I disassembled the valve in order to aid reassembly, but that's just me.

 

[Howey Matt]

I would have paint-marked them as I disassembled the valve in order to aid reassembly, but that's just me.

There's gotta be a way to tell how to install the spools without just relying on how they came out. What if the problem is that they weren't installed correctly in the first place? I can't believe the service manual doesn't contain this essential information. I'm going to call the dealer and see if they know.

 

[92U 3406]

I feel your pain. Had to do a valve stack out of a 24M and the bonehead before me literally threw everything into a box and left me to figure it all out.

 

[Nige]

I'm going to call the dealer and see if they know.

Unless they contact the factory and request engineering prints it's unlikely.

 

[Howey Matt]

Unless they contact the factory and request engineering prints it's unlikely.

The dealer says they don't know how they're installed either. The guy I talked to said they don't even try to troubleshoot valves -- they just replace them. Seems crazy to me, but now I know why dealer repairs are so expensive. I guess I either have to (1) buy a new valve, or (2) figure it out through trial and error (and drain and refill the hydraulic fluid each time).

 

[John C.]

If you study the hydraulic schematic, and compare what you see in the drawing with the actual spool and the outputs of the valve blocks, you should be able to see the logic in the position of the spool in the valve. The schematic is the ultimate representation of the internal parts of the system. The photos are only illustrations of someone doing the work and many times are wrong anyway.

 

[Howey Matt]

If you study the hydraulic schematic, and compare what you see in the drawing with the actual spool and the outputs of the valve blocks, you should be able to see the logic in the position of the spool in the valve. The schematic is the ultimate representation of the internal parts of the system. The photos are only illustrations of someone doing the work and many times are wrong anyway.

Or Cat could just make a note in the service manual about which way the spools go... Seems like one of the more essential pieces of information for a manual that describes how to disassemble and assemble valves, but that's just me.

The guy at the Cat dealer said they would defer to the parts manual for the spool orientation. I did the same and I'm still having problems. Boom won't go down, won't swivel left, etc. I spent hours switching the spools around without luck.

The dealer says they can rebuild it, but now I know they're just sending it out. No sense in paying them to be a middleman. My local hydraulic shop says they can rebuild it for around $100 per section, so $1,200 - $1,300 and I should be able to drop it back in the machine and go. I'll give that a shot and see how it goes.

 

[John C.]

I've not seen anyone make a note on the spool orientation in words or photos in a service manual. I've also never seen a parts manual with enough resolution in the drawing or photo that would definitely show or say which spool fits in which hole and what orientation it should be in.

 

[Clguest]

Or Cat could just make a note in the service manual about which way the spools go... Seems like one of the more essential pieces of information for a manual that describes how to disassemble and assemble valves, but that's just me.

The guy at the Cat dealer said they would defer to the parts manual for the spool orientation. I did the same and I'm still having problems. Boom won't go down, won't swivel left, etc. I spent hours switching the spools around without luck.

The dealer says they can rebuild it, but now I know they're just sending it out. No sense in paying them to be a middleman. My local hydraulic shop says they can rebuild it for around $100 per section, so $1,200 - $1,300 and I should be able to drop it back in the machine and go. I'll give that a shot and see how it goes.

I would have thought that if the dealer did not have an adequate answer wrt valve orientation when rebuilding then they would get the needed info from the Cat service rep. The service rep might have to go to the design group for the info; but certainly the info can be provided...and I would say, should be made available when requested.