JD3720 & 447 backhoe hydraulic hose replacement

[Yourkie]

If you don't mind I like to run even relatively minor tractor repair jobs past others that may have had some experience, unless I've done it before, and in this case I have not. Replacing the leaking hydraulic hose seems like a straightforward deal. The leak hasn't busted out but it is leaking enough near the lower BH pivot point that it needs replaced and as the fluid will damage vegetation for starters. Actually I can't tell which bucket hose is leaking because the hoses are covered in nylon cover shields and the hose(s) that I suspect are the culprit go up through the boom to the bucket cylinder. I'll probably remove and replace both.

Planned Procedure: Extend both booms straight out and rest the bucket on a wood block for best access and to relieve pressure. Shut off engine and work controls to relieve hydraulic pressure on lines. Remove cable ties securing nylon sheaths. Remove the connectors and hose fittings at the cylinder and also at the pump end. Remove hoses and cover sheaths.

Is there a recommended way to remove these fittings as they have a locking nut and another hex fitting? Will the cylinders and pump end require that the openings be plugged with something i.e. stopper, cork etc to keep hydraulic fluid from siphoning or leaking out? Will the system purge itself of air once the new hose is reinstalled? Is a thread seal required on new fittings? Are new O-rings required or are these typically compression fittings? Is there a bleeder valve that must be opened to purge air? Appreciate any and all tips. I'm going to have these hoses made in a shop locally. I'll need to determine PSI. I would assume from nomenclature on original. Thanks.

 

[Billrog]

Loosen the lock nut unscrew the fitting, plug the holes to avoid contamination,You'll see if it uses O rings once you have it off , double braided wire H hose will deal with the psi and you don't have to worry about purging a couple cycles once it's back together and the air will be out.

 

[truckdiagnostics]

I am going to make some educated guesses. First off the best thing you can do is clean everything first. Keeping the fluid from draining out of the cylinders and components is nice, but fittings need to be capped to keep dirt out. Your cleaning things to keep dirt from falling into opened fittings after you have removed them. What you are looking at and calling a lock nut chances are it is the swivel end of the hose, other end won't have that. You would have to hold the "lock nut" then turn the fitting, the swivel end has to come off first other wise the hose twists up. Then you can remove the fixed end, if done that way, because the hose is loose and can now turn with you when you are loosening it. Most time won't have two swivel ends on a hose is possible though. Next thing and i can not stress this enough, you have to have two wrenches that fit snug, no adjustable wrenches. You round the ends of those hoses off and life is going to suck. chances are you have NPT fitting going into the cylinder and yes there will be thread seal. depending on what type they used may have to over come that to get it loose. I bought one of these just for heating up hydraulic fittings so they cold be removed. New and Improved Original Heat Induction Tool | BOLT BUSTER - HEAT INDUCTION TOOL Allows you to heat things up with out fire and burning up your tractor. If it ia an NPT end use a hydraulic thread sealer, do not used Teflon based use one for hydraulic fittings. You mess up and get Teflon in your hydraulic system life is going to be bad. Don't believe you need to bleed it should bleed itself when you actuate it. At least I have never bleed my hoe when I have to replace hoses. pictures would be helpful

 

[Billrog]

Last post explained much better than me good advice.

 

[BukitCase]

Here's a couple links that should come in handy -

http://www.discounthydraulichose.com/v/vspfiles/downloadables/thread_guide.pdf

Hydraulic Fittings and Flanges | Fittings & Couplings content from Hydraulics & Pneumatics

Keep in mind that (just to confuse the issue) some fittings go by several different names for the exact same thing -

SAE, straight thread O-ring, O-ring Boss, ORB - all the same fitting.

37 degree flare, JIC - same fitting.

NPT - National Pipe Taper (standard pipe thread in U.S.) NPTF - the F stands for Fuel - not exactly the same threads, but compatible with NPT, with proper sealant. I use this

Loctite 303420 32429 545 Pneumatic and Hydraulic Fittings Thread Sealant, 10 mL Bottle: Arts And Crafts Supplies: Amazon.com: Industrial & Scientific

I agree with all previous comments - especially the adjustable wrench thing - besides, in a lot of cases you can't even get enough ROOM for one. I have 2 tractors and a Case backhoe, and ended up buying a couple different sets of specialty wrenches in order to keep from messing things up -

Amazon is currently out of stock, but google V8 wrench # 814 - that set plus a standard combo wrench set up to 1-1/4" would get you there. The V8 set is open end on both ends with different head angles.

HTH... Steve

 

[Yourkie]

Thanks guys....I appreciate you taking the time to discuss this up front which helped. Info on hydraulic fittings interesting to someone like me that has not had much hydraulic experience other than brakes. I'll post a couple of pics of ends. I removed the hoses by putting a wrench on the hose end and another on the locking fitting (middle hex head). Once the hose end and locking fitting (Lock nut)are loosened the locking fitting can be easily un-threaded from hose end, as it is free to turn on the adapter end. If that makes sense. The fittings at each end of the hoses are essentially the same.

I don't have access to hoses today so it will wait until Monday.

Question: I assume that the adapters (including swivel locking fitting) that thread into the cylinder and pump body will not need to be removed and replaced. Any thoughts there? That's what the guy at the hose shop said. He said only replace what comes with the hose. One thing that held me up was locating a stress relief clamp inside the boom that needed to be loosened so that hoses could be removed. I don't have them out yet but will finish today.

PS: Not to hijack my own thread but I have several small painted areas around fittings where surface rust developed only on the backhoe and I want to remove the rust and refinish. It doesn't sit out in the weather nevertheless there is some rust. Deere has had finish problems (paint peeling etc) on certain equipment over the years. My 755 required Deere to replace many painted metal panels (fenders etc) back in the early 90s because the paint peeled off. They used a new paint process. I've thought about using a Dremel with a small wire brush on these and then priming and painting or something else if mill finish.

 

[truckdiagnostics]

looking at it it looks like your hoses have no swivel in the ends and it is built into the adapter. Chances are the hoses have a JIC end. If hydraulic fluid is not leaking at the adapters do't replace them. and if they are JIC or o-ring boss you won't need a sealer.