JD 350 Backhoe Leak

KenP · Post by **KenP** » Mon Apr 06, 2009 8:02 am

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jdemaris · Post by **jdemaris** » Mon Apr 06, 2009 1:20 pm

KenP wrote:My JD350 Crawler/Loader has a Type 93A backhoe with a persistant hydraulic leak from one of the control valves.

In most cases, there is no fix. The high-pressure sealing is done by the smooth polished surfaces of the spool and bore. They get scored over time, and once that happens, they're going to leak- forever. The o-rings are more or less, dirt and residual oil seals, not pressure seals.

We used to fix many by replacing individual segments - which I assume are not available anymore.

townlineterry · Post by **townlineterry** » Mon Apr 06, 2009 5:31 pm

Have disagree with jdemaris on this. Had the same problem with the contol valve on my Case backhoe, and replacing o rings solved the problem. Having said that, the Case may have a different internal setup and I could be wrong when it comes to the Deere.

Bottom line, o rings are cheap, valve segments are not. So it is worth trying the o rings first.

digitup2 · Post by **digitup2** » Mon Apr 06, 2009 7:26 pm

Those single hydraulic valves can easily be repaired with an o-ring kit. Keep the o-rings lubed when you install them, with hydraulic oil. This will keep the o-rings from binding or ripping. Because John Deere dealers didn't do this doesn't mean that it can't be done. Just keep the area super clean and don't worry about a little bit of hydraulic oil.

If you can't get the kit from John Deere, you should be able to get it from Bull Dog Hydraulics.

Good luck

Digitup

KenP · Post by **KenP** » Tue Apr 07, 2009 4:12 am

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digitup2 · Post by **digitup2** » Tue Apr 07, 2009 6:41 am

If the old set lasted 40 years than the new set should pay for them selves .A o ring has two enemy's dirt and time.You don't want to put many hours on those old crawler mounted hoes but they can do a job well and a lot easier than a shovel will .I got a 9500 hoe off my 555A sitting behind the shop and every time I look at it I feel a cold sweat on the back of my neck .Even the older backhoes are too much for a days work for me now .I must be getting old or soft I know I couldn't put a days work on one now without someone carrying me to the pickup after .Digitup.

jdemaris · Post by **jdemaris** » Tue Apr 07, 2009 8:18 am

KenP wrote:Thanks for your replies. Spent some time researching this yesterday on the web and find that replacing the o-rings is a good first step if for no other reason than cost and availability of parts.

Yes, o-rings and seals are cheap and certainly worth trying. But, as I said - the high pressure sealing in those Gresen valve-bodies is done by the polished surface of the spool inside the polished bore - and NOT the o-rings. If your spools and bores are scored, no o-ring is going to fix it. If they are NOT badly scored - then you're fine. It's just plain not as simple as some have suggested - at least not in the long run. Especially backhoes since so much dirt tends to fall into the valve-spools and grind them up. We had countless service calls with dripping valve bodies in hoes. Needless to say, most customers - if a first time experience, would rather buy a 30 cent o-ring over a $100 or $200 valve section. But, the 2nd time around, with labor charges, the new section got put in. Can't say I kept a strict count, but we probably had a near zero sucess record with scored valves patched up wth o-rings.

Think about it a bit. How is a round o-ring going to stop a high pressure leak from running down a gouge/score? It's not, at least not after it gets used awhile. Hydraulic cylinders are a bit different, especially when Chevron type packings are used, because those packings pressure energize and fill voids.

Pretty much the same sort of thing with the Webster and Cessna gear hydraulic pumps. Seal in front is for residual oil and dirt only - and not high pressure oil. Resealing will sometimes work temporarily, that's all. Pump also relies on smooth metal to metal for high pressure sealing.

jdemaris · Post by **jdemaris** » Tue Apr 07, 2009 8:25 am

townlineterry wrote:Have disagree with jdemaris on this. Had the same problem with the contol valve on my Case backhoe, and replacing o rings solved the problem. Having said that, the Case may have a different internal setup and I could be wrong when it comes to the Deere.

Bottom line, o rings are cheap, valve segments are not. So it is worth trying the o rings first.

Since you say you disagree with my comments, I assume your valve spools and bores were badly scored in your Case?

KenP · Post by **KenP** » Tue Apr 07, 2009 9:15 am

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jdemaris · Post by **jdemaris** » Tue Apr 07, 2009 10:38 am

KenP wrote: As I said, I don't see a lot of alternatives.
Thanks, KenP

Yeah, the idea of replacing sections in anything is often moot after the machine is 10-15 years old. Deere et. al. don't make the parts and can only sell what they can get from their vendors. Years back, Deere bought such parts with supply-agreements that had expiration dates. Now, I don't have a clue how these things are done. Same with new cars and autos. Last I read, Federal Law says parts only have to be available for 7 years from the OEM. So, you can buy a new $50,000 truck from GM and in seven years, they can stop selling parts if they like. Actually, that time-frame might even become shorter, considering the government pseudo takeover.

I know in the 80s, many original sections for 60s-70s machines were not available.

Also, many hoes don't even use sandwich-sections. I've got an old Sherman hoe here now and the entire thing is a one-piece casting.

As I said in my first statement, new o-rings alone are not going to fix a badly scored spool or bore. Even if the o-ring could fill the extra void, it's life would be shorter. I have, however, seen many get patched up just by fillling in the deep scores with metal-epoxy and smoothing with emory paper. We used the Deere brand which was Devcon at that time. Real good stuff. Deere also sold it to fix loose splined axles and hubs on tractors, log skidders, etc.
Ever seen a 1010 or 2010 wheel tractor with the hubs loose and wobbly on the axles? The Devcon worked miracles on them.

Chances are, you're using your macine where a few drops of oil on the ground won't resulting in the environmental police coming to your door. But, machines used on a daily basis in public can't leak a drop. In part, that's what led to the death of the two-stroke-cycle Detroit. When I last worked for Deere, it got so that we couldn't even do 100 hour services on new crawlers anymore if they were out in public. That because it's almost impossible to do so without losing some oil onto the ground. Especially a 350 reverser filter change.

digitup2 · Post by **digitup2** » Tue Apr 07, 2009 6:54 pm

Before I wouldn't through out any large negative ideas yet .I would just look and see if a o ring is split or broken I have only replaced a couple of valves in my days and quite a few o rings have been replaced in that time certainly on older equipment that has been sitting for some time then had pressure put to it and of corse it leaks.Tollerance alone nor the o ring alone seal the oil in they have to work together and usualy do till one or the other fail.Just watch for an o ring break or crack this is all it takes under that kind of pressure All I am saying is try some o rings and see how that works first .We don't know if the bore is scored or not yet if it is still shinny lube up new o rings and try them .Digitup.

Tiny Crawler · Post by **Tiny Crawler** » Tue Apr 07, 2009 8:15 pm

O-rings loose their original Durometer (http://en.wikipedia.org/wiki/Durometer) over time so repacking useually can fix most leaks.

But yes is could be scoured, and it will eventually leak if it is scoured and only the previous owners know how much wear and tear they put onto the machine.

If you can get clearance for the spool and pull it out you can just fix that one, and not have to take apart the hole valve body. Sometimes band aids work longer than you think..

FYI,
I repacked my valve body for a 51 backhoe a couple of years ago and was able to cross reference all of the o-rings, backup washers, and even the nylon balls from McMaster-Carr http://www.mcmaster.com/# and really saved some cash instead of buying the John Deere Kits, fixed all of the leaks on the loader and backhoe valve body for around $100 and replaced the o-rings for the JIC connections that attached to valve bodies as well.

Also do not try to scrape the o-rings out with a metal pick, they make brass picks you can use, (McMaster-Carr Sells them) This can usually be the scour , Also you can coat the o-ring with Vaseline to lube it up to install it and the spool.

Hope this helps you..

KenP · Post by **KenP** » Wed Apr 08, 2009 5:09 am

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mini kahuna · Post by **mini kahuna** » Wed Apr 08, 2009 8:53 am

you will probably slow down the leak some with new o rings but as said above the spool valve assembly is worn past service limits.
had a case backhoe with the same thing,oil passing under pressure,no spools made any more,put new o rings in and it went from a quart a day to 3/4 a quart a day.
old machines are just that old,I am 43 years old and my o rings could use a change out too!!!
take it easy on the old girl,give the o rings a shot can't hurt thats for sure.

KenP · Post by **KenP** » Thu Apr 16, 2009 1:43 pm

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