Spool Valve Leaking out of open hole? Some type of cold plug maybe? *Pictures*

[halfspec]

Good afternoon

Please be gentle. I'm a very new tractor owner and I'm also only an electrical engineer by trade, so I'm having trouble even coming up with the right way to describe my problem. I'm hoping someone can just name what I'm looking at and maybe point me in the right direction so I can do some research.

I'm working with a Bush Hog 665H Backhoe connected to a 2012 New Holland TC33D.
I noticed soon after buying the tractor that working the backhoe arm from side to side would spurt out a little bit of hydraulic fluid every time I moved it. This type of spurt adds up pretty quickly, so today I started tearing down the backhoe to see where the leak was coming from. Please excuse the mess. I was just as surprised to see how much junk had accumulated behind the panels:

This is the spool valve in question that leaks from the bottom:

Specifically, the small silver canister at the very bottom of the valve.

A shot from below shows an open hole that the fluid spurts out of when actuating the valve:

It's almost like the spurts are a relief action between the spool valve states of open / closed.

The problem I think I see is that all the other spool valve bottoms are capped / plugged. This is the only one that's open. My question is, what's supposed to go here? Is it supposed to be capped / plugged? If so, I assume it can't be a bolt since there isn't any threading in the hole? Is it something pressed in like a cold plug? Any ideas why it would have popped out in the first place?

I've looked through my 665H Backhoe manual but the spool valves aren't covered in this type of detail.

Any help is greatly appreciated.

Lane

 

[TractorTech]

Lane, welcome to TBN. Great pictures and description. Not sure what is supposed to go in the end cap if anything, but that spool valve (bucket or swing circuit?) has a leak at the bottom seal of that spool, located under that cap. If you remove that cap, it most likely is full of oil from the leak or squirting oil. Attached is a the link to the diagram/parts list for what is available for that valve.

Bush Hog 665H Backhoe Parts

Bush Hog 665H Backhoe Parts

www.messicks.com

 

[BeezFun]

That silver canister covers the spool when it extends from the bottom of the valve. If you don't know what's inside a typical hydraulic directional control valve, this youtube video shows a basic valve. In that video the left end of the valve is the silver canister on your valve, and the spool extends into that silver canister when you move the lever. There are two things that prevent the hydraulic fluid from leaking out of the valve. The high pressure seal is provided by the metal spool fitting very tightly inside the metal valve body. This is probably the most carefully machined part on the tractor. So if it gets worn, scratched by contamination, rusted, etc, it will leak oil into an area that is normally sealed by an o-ring that only provides the low pressure seal for the tiny amount of oil that normally gets past the high pressure seal. The video doesn't show the o-ring, but they are around the spool and if the high pressure seal leaks, the o-ring has no way of stopping the oil. Given your description I would guess the spool is leaking. I think the small hole you're looking at is a drain hole in the bottom of the canister which allows moisture that condenses or leaks into the valve to escape. I've never seen a hole offset like that, it's usually a hole in the bottom of the canister. Maybe I can't see exactly what the canister looks like.

One way that valves typically get damaged is if they sit outside in the rain and the rubber boot around the actuator allows water to enter, which causes rust, which leads to a leak. One thing you can do to further diagnose the problem is to remove that silver canister and confirm the oil is escaping around the spool. It should be easy to remove if it's not obstructed by other parts. There shouldn't be any small parts that can fall out when you remove the canister because this is not a detent valve, but I would put a towel or magnetic tray under the canister just in case. If the spool is really leaking, you'll need some more guidance.

 

[halfspec]

Thank you so much for the help @TractorTech & @BeezFun. Just talking through the spool valve parts helps my tremendously to understand its operation and what the individual parts are called so that I can know what to look for / fix.

TractorTech: It's the spool valve for the main boom cylinder. I believe, from the Messicks link you provided (Thank you!) it's the "Control Valve Section Typical Section For Lift Circuit" or the only control valve that features a Float Spool Positioner which seems to require a bigger bonnet. This seems to track in my situation since the leaky valve is the only one with a bonnet this big.

BeezFun: Thank you very much for the deep dive / explanation + the youtube video. It was extremely helpful for someone at my level and I really appreciate it. I don't know the life story of this backhoe unfortunately as I've only owned it a year. The top of the spool valve actuators is obviously a mess and it looks like it might have had something nest in it at some point. Still, the paint isn't faded to the point that I would worry its spent its life directly in the elements, so I'm hopeful the top seals are good enough that they haven't let water / rust into the spool. I'll be taking a closer look before ordering anything. I'll also remove the bonnet and actuate the spool to see if I can get a better idea of where the hydraulic oil is leaking through.

After digging through my manual I found that it does go through the float bonnet assembly. I just didn't know enough at the time to know what I was looking at:

It also has instructions for resealing the spool from the back and front:

Looking at Messicks parts catalog for the Bush Hog 665H Control Valve Section Typical Section For Lift Circuit:

I think the 92556 Spool Seal Kit; consisting of: 32 (qty. 1), 28 (qty. 1), 38 (qty. 1) and 39 (qty. 1) is what I would need as it looks to reseal the bonnet's o-ring and U-cup seal as well as the top of the spool.

Thank you again for all your help fellas

Lane

 

[TractorTech]

Good luck Lane! The float detention assembly can be tricky to assemble. Make sure you disassemble the valve on a bench and floor area clear from clutter as the balls will fall out and can be hard to find once the hit the floor.

 

[LD1]

Seems like you have a good understanding and some good diagrams so not much I can add other than:
IF it were mine....

Id powerwash the area real good....then remove the whole valve assembly from the machine. Label things VERY well so you know exactly where things go back. You'd be surprised how many posts here on TBN of hydraulic issues where something isnt working or acting right.....and someone swears they put it back together exactly how it came apart.....but come to find out they mixed up a few hoses.

After its out.....take it to a clean area for disassembly and inspection.

I'd also make note how many hoses hook to the backhoe......if there are only TWO that connect from backhoe to tractor it is extremely important NOT to use the 3PH while the hoe is attached. Even if the 3PH arms are removed and you cannot "actually" use the hitch. Most manuals tell you to lower the hitch lever all the way and DONT move it until the hoe is removed and the hoses are coupled back together.

Reason is, with two hoses, the backhoe valve doesnt have PB. And by moving the 3PH lever you are putting backpressure on the tank passages in the backhoe valve and can blow out the spool-to-case seals and make the valve leak....similar to what you have now.

 

[halfspec]

Thank you again @TractorTech and also @LD1. Thankfully I've got a 20+ years of experience working on cars that includes a couple of frame ups and a dozen engine swaps so I've learned to be meticulous, and I've got a lot of tools to throw at the tractor. I would agree with both of you and my preference would be to thoroughly clean and the valve assembly, then completely remove it from the backhoe for repair.

My only concern at this point is budget creep. Specifically, creep associated with disturbing the valve array. My understanding of the array is that each valve is sealed to its neighbors and that if I disturb the array, I'd most likely be looking at resealing all the mating surfaces between each valve. I'm having trouble figuring out exactly which seal from messicks represents this valve to valve seal, but my best guess is that it's #40 in the diagram above as it seems to be a common part number associated with each valve section and the diagram sorta looks like its trying to show its placement on the side of the valve body. It's a $46 part... x 7 = $322. Does that sound right to everybody?

I guess that just has me second guessing whether doing this DIY is the most cost effective way to do this. Are their valve repair specialist (board sponsors or other) that might be able to match what's looking like a $500+ (in parts alone for me) repair? I only ask because I've run into specialists in the automotive field, transmission rebuilders for example, that know their product so well that they know all the seal's dimensional / material specs and can buy the non proprietary seals in bulk freeing them from the constraints of buying inflated factory seal kits but retaining a quality repair. Is this something that's common with tractor valve rebuilds?

@LD1 - Thank you for the hose heads up. The back hoe attaches in series with my FEL when attached and is like you suspect, two hoses. Disconnecting it simply requires removing it from the loop and reconnecting the FEL directly to the pump. I'll make sure I get the backhoe supported and removed from the tractor before I start working on the valve assembly

Lane

 

[LD1]

Usually what seals between the valve sections is nothing more than o-rings. Once apart it can be confirmed then just replace the o-rings when you put it back together. Might have to measure to size them up, and most o-rings for hydraulics are a little harder than common o-rings. Usually a 90 durometer instead of 70

 

[halfspec]

@LD1 Thanks a million! That makes me much more comfortable getting started. I can measure o-rings all day long haha. Thank you for the durometer tip as well.

Lane

 

[LD1]

The part you are referencing that shows seal retainer just appears to be the plate that is bolted to the top side of the valve where the spool protrudes out of the valve body so the control lever/linkage can attach.

Between valve sections though, all of the valve sections I have seen are sealed between each other with o-rings. So it makes it easy to make a 3, 4, 8, 10 spool valve. However many you need.....just need longer bolts (or all-thread) to sandwich them all together.

Here is an example of a valve section Bailey BSV-3 Series Sectional Valve Component - Assembled Work Section, 1S/18L/E8