450C Crawler w/Backhoe blowing hydraulics

[Accampbell63]

Hi All,

Thanks for the acceptance into the J.D. Crawler Forum.

In the past I’ve owned a JD 350 Crawler loader,great machine, but Iv’e since upgraded to a 450C (1980 model according to the serial number) with a 9300 Backhoe attachment (according to the gentleman I purchased it from, have not verified it yet)

The issue I’m having is when the backhoe is hooked up and I’m using it, it’s been blowing hydraulic lines, cylinders and finally it blew the top of the Boom lift valve. The first several things I chalked up to just having an older unit, but blowing the valve assembly apart, I’m thinking to much pressure.

Upon inspecting the backhoe hydraulic lines I found the Pressure line to the Hoe was plumbed directecly off the “outflow” port on the Boom valve, the return line from the hoe was then plumbed to the return line to the tank, creating one big loop. After consulting the manual I see where the hoe supply/pressure line is supposed to be connected from the the aux/diverter port on the opposite side of the valve body, with the return line from the how being attached I into the return line with a tee. Ive also bought another boom lift valve from Wegners in central Pa.

With all this being said I still have several questions. I’m not a hydraulics wiz by any means. I know the difference between an open and closed system, I’ve worked on closed systems that operated at 3,000 PSI, but that was following technical data with no variations.

My questions are.......With the way the hydraulic system was plumbed, is that possibly the reason why my machine has been blowing the hydraulics apart?

I’m in the midst of changing the lines to the way the manual says it’s upposed To be. It doesn’t say anything in my manual about adding additional relief valves or check valves. Is that something I should consider adding? I’m just tired of blowing things apart every time I try and use the backhoe!

Thanks in advance for any answers, I searched through previous posts but couldn’t find an answer.

[JWB Contracting]

Is this a loader or dozer? A loader normally uses a power beyond fitting in the loader valve that sends high pressure oil to the backhoe valve, which then gets returned to the tank. A dozer machine often uses a diverter valve so you can either use the dozer or hoe. We have rigged up dozers with flow to the hoe first with its own relief and then to the dozer with its own relief set a bit lower. Big power for digging and lower power for dozing. Reverse of what Deere intended.

Does your machine sound like the hydraulics are screaming at you, possibly the return connection from the hoe is not connected. Try disconnecting the backhoe quick couplers and hook the tractor ends together and see if the loader operates normally.

The main relief is on the loader valve. I would lower the pressure if you can’t find anything else wrong.

[original possum]

I am not sure by your description but it sounds like the pressure line is on the wrong end of the valve block. Make sure it goes past the relief valve on its way to the control valves. I HAVE seen backhoes plumbed backwards. They blow hoses or pumps.

[Accampbell63]

Thanks for your quick responses!!!!!

It’s a loader......

The lines to the hoe were hooked up correctly. I’m gonna try to attach the hydraulic diagram showing how it was hooked up.....the yellow indicates the port that IS NOT CONNECTED at this time, but I’m in the process of connecting it. Along with adding the a tee connection for the hoe return flow as the diagram indicates it should be plumbed for the hoe.

[Accampbell63]

Okay so apparently I’ll have to jump on the computer to see if I can post the hydraulic schematic......I phone apparently doesn’t work.....lol

[Accampbell63]

HI Guys,

It's been a month or so since posting my hydraulic woes of trying to get my 9300 backhoe up and running on my 450C Crawler Loader without blowing things apart. I've done hours of research, searching this site, and a few other message boards. Here's where I'm at...........Still have questions!!!!

I removed the pressure line from the "Out" port of the loader main boom valve, attached the pressure line to the power beyond port of the aux. hydraulic valve. I should mention that initially I attached a line from the "Out" port of the loader main boom valve and Tee'd it into the Tank return line like the manual shows, Problem was I had no hydraulic pressure going to the Backhoe. I saw a post on this message board stating that the "Out" port needs to be plugged, so I Plugged it and Bingo, now I have pressure to the Backhoe, but only one return line (coming from the backhoe) back to the tank. Since the diverter/adapter fitting that the manual calls for limiting the flow to 23GPM is no longer available, I ordered and installed a adjustable flow valve and installed it on the supply line coming from the power beyond port. I called my local hydraulic shop to order the adjustable flow valve, telling them I need one that can handle 30GPM flow with an adjustable pressure relief valve that I can adjust up to 3000PSI to act as a system relief valve. The valve they sold me was a Prince RD-100, this particular valve has an "In" port, "Out" port to supply the desired piece of equipment and an "Excess" port that diverts the extra fluid back to the tank. I was also told by the salesman that this particular valve has an internal pressure relief valve that at 3000PSI will divert excess fluid through the same line when pressure exceeds that limit.

After many trips for fittings, hoses, more fittings I get the RD-100 valve installed, the excess overflow tee'd into the return line I'm ready to start tearing STUFF up! Start up my official 1980 John Deere 450C , carbine action, 200-shot, range model Crawler with a compass in the Dash and this thing that tells time!!!!! Front loader works, after running through several cycles I top off the Hydraulic fluid, now it's time for the Backhoe. I run it through it's paces (after plugging the "out" port) top off the hydraulic fluids again, and start tearing things up fooooor ...........about 5 Minutes!!! BOOOOOM blow the top of the Aux loader valve apart

After hours of research AGAIN, numerous phone calls back to the hydraulic shop, the John Deere dealership I finally call Prince for a definite answer concerning the RD-100 adjustable flow valve. The tech at Prince explains that this particular valve is "Pressure Compensated" and in no way should be confused with "Pressure Relief". So that explains why I blew up the Aux Valve. BY the way I talked to the owner of the hydraulic shop, explained that he sold me a part that did not meet my specifications, then lied to me about the part stating "yes it has an internal pressure relief system".......His reply was "It does have an internal relief, they don't know what they're talking about"!!!!!!!! So much for doing business with him anymore!


Since the 9300 Backhoe does not have a system/pressure relief valve I know I have to install one on the pressure line to the backhoe. But what kind? Direct-acting relief valve or pilot-operated relief valve? What pressure do I need? The 9300 Boom Raise circuit relief valve is 3500 PSI, so do I need a system relief valve that will go that high? Also I've been thinking (which is dangerous for me at times) should I reroute the pressure line from the Aux. power beyond port, tee it into the main pressure line coming off the pump (in between the loader valve and pump) plug the Power beyond port and try to reinstall a return line from the "Out" port on the loader boom valve to tank? This would increase return flow and hopefully help reduce the pressure build up.

Any and all comments, advice and criticisms are welcome. I'm just tired of blowing hydraulic parts up, and this is getting rather expensive!!! I just wanna dig some dirt! Thanks for taking the time to read my sorrowful and frustrating story. Have a nice day!!

[JWB Contracting]

Here is my understanding of how a hoe hydraulic system should be plumbed

Pressure oil to loader valve

Return line from loader valve to tank

Power beyond fitting installed in loader valve

Hoe supply line installed into power beyond

Hoe return line tied into return side of tank, tee with loader return

I would disconnect the hoe and test your relief valve in your loader valve.
Loader machine

There should not be any need to plug anything off.

Potential problems

- closed vs open center valve on hoe. Hoes were a factory option on loaders and skidders which have the wrong valve
- hoe input / output lines crossed
- relief valve in loader valve not functioning
- pull power beyond fitting and confirm its correct.

The only time you would need a separate relief is if oil came from the pressure side of pump, to a relief, to hoe valve, to loader valve pressure side. This way you can set the pressure separately for the hoe vs front attachment. We did this on dozer machines to eliminate the need for a diverter valve. Just removed this kind of set up from a widepad 350 we converted back to narrow track and removed the hoe.

[Accampbell63]

Thanks for your reply. I honestly thought the loader system relief valve may be faulty, but since I can run the loader for hours at end and nothing blows up I dismissed that. I will definitely check once I get the aux. valve replaced. So if I'm understanding this correctly (please forgive my hydraulic ignorance) the system relief valve for the loader also covers the backhoe pressure?

I was told by my local John Deere dealership that The power beyond fitting is no longer available. They couldn't even give me the old part number, my thinking was with the part number I might be able to track one down. Any idea where I could track down the correct fitting down?

I initially had the lines installed as you described less the power beyond fitting. I didn't have any pressure to the backhoe, that's when a friend who has a 350 loader with a hoe recommended plugging the outflow port on the loader boom valve. Could this have been caused because I didn't have the power beyond fitting installed?

As for the potential problem you described. The only one I know is 100% correct is the lines pressure/return are run correctly to the hoe. The pressure line is attached directly into the hoe valve body, the return comes out into what looks like a tank, then another line from the bottom of the tank of the hoe which runs into the tank on the loader.

I read somewhere that the 9300's were all open center valves, I haven't checked but I will.

Here's something I haven't mentioned. Both times I used the hoe I noticed that there was a sudden drop of RPM's almost to the point of the engine stalling then BOOM the loader valves blew apart. Definitely somethings amiss, I appreciate any and all the help! Thanks again!

[DrLoch]

Can you could, please post a crude hydraulic schematic of how you have this plumed before you seriously injure yourself or someone else. Injection of hydraulic oil into bloodstream is a very serious thing that could kill you or someone else. I would also like to suggest you stop using this machine in that mode of operation until you have it operating correctly.

Not trying to be an A%%H*%$#@ about this, but, something is clearly not correct and your method of troubleshooting is not working. I am a certified Fluid power person which has been designing, building and integrating hydraulic and electro-hydraulic systems for close to 50 years.

I will PM you with an email address you can send it to If you can't post up the circuit.

[Accampbell63]

DrLoch

I agree with you! I also appreciate any and all help. I plan on disconnecting the hoe as soon as I get the replacement aux. Valve installed until this gets figured out.