The last few weeks I’ve had a leak develop in the center of the backhoe valve bank. It looks to be leaking in between the stabilizer valve blocks. I removed the spool caps and it definatly is not leaking out of the spools. I have ordered new O-rings for the valve bank. Just the ones used between the valve segments. Does anyone know the torque specification for the 4 tie bars that hold the assembly together? I have a service manual but that chapter is not in mine(go figure)! I will be ordering caps and plugs to block off everything before removal. Planning to remove the control tower and floor plate and lift it into the cab for removal. Hope to get to it next week as we are having a serious heatwave here in Central NY.
That is unusual for those to leak, I have had a couple loader valve sections leak and that was due to the section cracking in the O ring groove, I never had a BH valve O ring leak between sections. If I were you while it is apart I would get it Magnafluxed, that's a bunch of work to take the chance.
I agree, if it isn’t obvious why it leaked I will find why. It is odd to get a leak like this. My worst thought is that the valve portion has cracked. Why it would, I don’t know.
I have replaced many cracked sections in the backhoe valve bank - most always the boom section - one swing section - never a stabilizer section. Reason for cracking, at a guess, is the spike in pressure - particularly when putting the hoe into overcentre to lock the boom. What to look for is below. I just use the dye check + developer in a spay can - it works well & you will see straight away.
doghead, I am no expert at backhoes, but I have inspected many parts, for cracks, while working on equipment. Below is a link to the product that we used (I am sure it is available elsewhere cheaper but this is a nice image). What I have found using this product, which does work, clean, clean, clean, then dry well prior to starting. Do not get impatient, wait the specified time for the penetrant to work. https://www.grainger.com/product/MAGNAFLUX-Penetrant-3WU63?
I may be incorrect and it is leaking between the boom section and the stabilizer section. I’ll look closer, to be sure. I was going from memory when I posted. Looks like $2700 For the boom section. I’ll check on availability Monday. In the mean time, I’ll confirm the leak position.
Some progress was made today. To start with I confirmed the leak was between the stabilizer and the boom valves. I removed the valve-bank from the backhoe. Cleaned it best I could and set it on a bench. I disassembled it to the boom valve section. Sure enough, the lower O-Ring was split at the top. Looking closely at the port, it appears to have a microscopic crack in an up and down direction near the top of the o-ring port and is visible inside the port as well. This was confirmed by two other peoples eyes with no prompting of where it was. So, after a bunch of internet searching and phone calls I determined the least costly valve that was in stock to ship today was $2600 + shipping. My local dealer was at $2700 and at least 10 days out. The valve body alone, is no longer available. I had been informed by the dealer that there were a couple revisions to the valve and the latest valve part number is 144321A7. This makes sense if they have been a problem. During all my searching of the internet, I found an eBay seller with 2 NOS of the 144321A5 version valves. He had them listed for $2000 with a make offer option and the ad was ending during the night. So I made an offer of $300 plus shipping. To my surprise, he accepted it! So that is my plan for now, to replace it with the same part that it has now(confirmed by my dealer). It lasted 20 years(12 in my ownership). I hope this is not a bad choice, but honestly given the costs, I feel this is a good choice. I do my own work so time is “free”. Airman, your input(experience) was the key to me finding the root cause of the leak. I would not have looked so closely for a crack if you had not shared your experience and posted such a good picture. Thank you very much for that. I also will fully disassemble the valve bank sections and fully clean them and reseal them all. I will also be resealing the spool valves while it’s on the bench. I still need to figure out the correct torque specification for the 4 tie rod/bars that hold the bank together (if I remember to ask at the dealer when I pick up the o-rings, I’ll post it here). Also, one other question, Does the valve come set to the correct pressures for the machine or do I need to test and set them after it’s installed? Thank you to all that have replied so-far. I really appreciate the assistance.
@doghead Glad to help out. Let's just say I've been down that road before.....be it a long time ago..... The new section should come with the secondary reliefs already fitted - & adjusted. The through bolts are tensioned to 30ft lbs. BTW - that $300 A5 section you bought is a bargain! - I hope it is brand new??
Yes, it is brand new.
I received the new valve today. It was in the original wrapping and Case box. New as advertised. Very happy about that. Same casting number. Looks perfect. The last of the seals and o-ring should be in tomorrow morning. I plan to assemble the valve bank tomorrow afternoon and finish resealing the spools. Hopefully I will get it installed late tomorrow or Saturday morning. Thanks once again, to all who read and or replied. I appreciate it. This is a great forum.
Looks like you really made out on this. Good for you!
I picked up the last of the parts needed this morning and got home to tackle the project. After stacking the whole valve bank assembly, I started the torque on the 4 tie rods. Going for 20, 25, them 30 ft/lbs. At 25, one of the tie rods stripped, the threads were slightly galled from disassembly. After trying a few different positions of the nut, I had to give up. I had to order a new one. Over $100 bucks for one 19” rod with an inch of threads one each end, from case. So, I threw a piece of all-thread through that one for now and re-torqued all to 20 for now to keep it dry and sealed. (On the bench) New rod should be in on Monday.
I forgot to mention, I did remember to ask the dealer the torque spec for the tie rod bolts. They confirmed 27-30 ft/lbs, from the service manual. Apparently the rods are grade 8 or 8.8. Max torque on 3/8-16 gr 8.8 is 44 ft/lbs dry and 22 lubricated. Gr8 is 33 ft/lbs.
The tie rod bot came in Tuesday. I did not have time until today to get back to it. So, this morning I torqued the 4 rod bolts to 20, 25, then 30 ft/lbs. Reinstalled the valve bank into the hoe. Connected all the hoses/lines. Added about 2 gallons of oil. Reinstalled the control tower. Started it and cycled all the cylinders on the backhoe and stabilizers. Topped off the oil with a bit more to get back to the full cold line. Lots of tiny air bubbles were noticeable and fairly quickly disappeared. Reinstalled the floor panel and floor mat. Ran it a bit more and all seems good. I’ll report back here if anything else shows up. For now, I think I’m all set. Thanks to all