John Deere 350 hydraulic system pressure relief valve o-rings sought

[briancady413]

The hydraulic system suddenly stopped working two days ago. I'd like to check, clean and maybe rebuild the hydraulic system pressure relief valve, so seek fresh o-rings:
R26375
and any within the system relief valve, which is numbered T13132.

Where one can get specifications on these o-rings, or get replacements?

Brian
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[Jim B]

Welcome to the Boards.

For a few O-rings you are going to be further ahead to just go to you JD construction equipment dealer and get them, than playing the let's match this up game. You will know the material, size, and durometer are correct this way. United owns both the ag and construction lines in your area. There is an Ag dealer in Greenfield, they might work with you on getting the O-rings. If you have part numbers that is usually all they need, sometimes the ag and construction don't like to cross lines. Since United bought the construction line they seem to be working together better, at least what I have needed here in Maine.

Have you checked the drive to the front pump? Those have been known to fail/strip out and the hydraulics go dead when that occurs. I doubt the relief valve is the problem to cause immediate loss of hydraulics.

A bit of housekeeping. Posts about your 350 should be on the Late Models Board. Don't be surprised if you find it over there as Lavoy or a moderator may move it when they see it. Not a big problem just how the models are separated here.

[briancady413]

Thanks very much, Jim B.

The shaft into the hydraulic pump is turning. I'm guessing that some particle is now jamming open the system relief valve - would you guess differently? Are there tests I can do? Now a few of the hydraulic cylinders move slightly when their control levers are opened, but with nearly no force.

I have both a service manual and a parts manual/catalog - The service manual's troubleshooting section says to replace all or some of the system relief valve, depending on the symptoms. The symptoms fit under all three replacement possibilities; upper part, lower part or entire valve.

I tried at the Greenfield United Ag & Turf to buy the entire system relief valve assembly, but they said it is no longer made. I'll ask about the O-ring(s) in particular. I thought I'd read that there are three O-rings, but I have only one part #. I guess the dealership can help me on this.

Brian
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[Jim B]

Do you have a 3000 psi or greater pressure gauge? Your service manual should give some testing procedures. If you take the main relief apart you are going to need a gauge to adjust it after assembly.

You may need a helper to check to see if the pump shaft is turning when the lever is moved to lift the blade. it might turn if no pressure is called for as it is an open center system. It does not build pressure until a valve is moved to activate a function. Just a check to be 100% sure before you go deeper.

A part number search on the John Deere site brings up T13132 as an adapter fitting on a 2010 tractor, which shows as no longer available. Is your 350 a straight 350 or one of the later ones 350 B, C, or D? The parts catalogs for the 350 loader and dozer blades are separate from the crawler parts catalog, including the hydraulic systems for them. Need to know which you have to look at a parts list for your attachment. Does your crawler have a loader or blade? If a blade what model?

[Lavoy]

I would say that the likelihood of a piece of crud jamming the relief open is virtually impossible. They check ball is like a small marble, when the system is bypassing, the flow past the ball would mean a quite large gap, so no small piece of anything is going to do that. There is another problem, just need to find out what it is.
Lavoy

[briancady413]

Do you have a 3000 psi or greater pressure gauge? Your service manual should give some testing procedures. If you take the main relief apart you are going to need a gauge to adjust it after assembly.

You may need a helper to check to see if the pump shaft is turning when the lever is moved to lift the blade. it might turn if no pressure is called for as it is an open center system. It does not build pressure until a valve is moved to activate a function. Just a check to be 100% sure before you go deeper.

A part number search on the John Deere site brings up T13132 as an adapter fitting on a 2010 tractor, which shows as no longer available. Is your 350 a straight 350 or one of the later ones 350 B, C, or D? The parts catalogs for the 350 loader and dozer blades are separate from the crawler parts catalog, including the hydraulic systems for them. Need to know which you have to look at a parts list for your attachment. Does your crawler have a loader or blade? If a blade what model?

The system relief valve relief pressure should be 2250 psi, according to the specs I see.

This is a 1968 JD350: serial # T-4E3D004175-I - as best I can tell - a crawler loader, with backhoe 93-A attached.

This hydraulic pump spins whenever the motor runs - direct drive. This is both from observation and reading.

Please forgive me, but I'm surprised to hear you say that 'It does not build pressure until a valve is moved...' Can anyone else verify that? I expected that, when no function valve is open, the system relief valve would open, relieving pressure from the always-on hydraulic pump. Thus a stuck-partially-open system relief valve would explain extremely low hydraulic power.

By the way, while adding hydraulic fluid got the tank level into the sight glass, what I see is not quite clear - it looks a bit milky, cream-colored.

Also, there is a hydraulic fluid leak, apparently from the inner rear of the hydraulic tank.

Jim B and Lavoy, thanks for your efforts - I welcome them, and suggestions on what to check next,

Brian
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[Lavoy]

Jim is correct. You have an "open center" hyd system which means the oil is always circulating at volume, but no pressure other than inherent loss to friction inside of lines and hoses. No pressure is developed until a valve is pulled, and even then, the bypass is not open unless the pressure called for to do the work exceeds the set pressure of the relief.
In my opinion it is virtually impossible that it is a relief issue, and exceedingly unlikely that it is a valve issue or any sort. Instantaneous failure is almost always a function of the pump, or pump drive. Until it has been definitively ruled out, and I don't mean just visually, I would focus all of my attention on the pump.
Lavoy

[Jim B]

Do you have a copy of the parts catalog for the JD 350 Loader, PC926? you need that to find the part numbers for the loader attachment, including the hydraulic components on the loader, such as the control valve. As I posted before, T13132 as an adapter fitting on a 2010 tractor, not used on your crawler or loader.

The hydraulic section (Section 190) of your crawler service manual (SM2063) should give you more info on how the fluid flows through the open center system.

Milky colored fluid generally indicates water contamination.

I have seen the coupling spline strip on the pump shaft and the pump still turn if no control is being operated as the pump will turn easily if it doesn't have to develop pressure. A hydraulic function has to be operated to make the pump develop pressure, while checking to see that the actual pump shaft itself is turning, not just the drive to it.

I agree with Lavoy on ruling the pump out first. I think even with a relief stuck open a bit; functions would be weak but not stop entirely.

Look closely at your serial number tag. There are a couple things that don't look right.

Machine serial number tag breakdown using the 350 Introduction from the JD 350 Parts Catalog:

SN = serial number
T = Tractor
4= JD350
E= Crawler - Loader
3 = Diesel
D= Sliding Gear Transmission, with reverser

Serial number: 6 digits (The 1964 serial numbers started at 010001. Your number 004175 is lower than the first one given here in the 350 serial numbers on the FAQ Board)

T= (Build location) John Deere Dubuque Works (I think the I you posted is actually a T).

Does your crawler have a diverter valve to swap the hydraulics between the hoe and loader? If so, check to be sure it has not gotten out of position.

[briancady413]

JIm B, thank you for your thoughtful, detailed reply.

- I have a PC-921 parts catalog, not the correct PC-926 one. I'll check the service manual section 190, on hydraulics.

- Sorry about the wrong serial number - I'll get the right one again today. I think I got the serial # from the wrong place, for a part, not the crawler.

- I'll get help to check whether the hydraulic pump drive coupling splines are stripped, then open valves to lower the boom into the ground and have my -friend see whether the pump shaft turns under load.

- I guess I need to drain the milky hydraulic fluid and replace it with fresh stuff. I read that the loader hydraulic system capacity is 12.5 gallons. I'm not sure how to get water-contaminated hydraulic fluid out of the cylinders.

Brian
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[briancady413]

Two friends have recommended cleaning / checking the hydraulic fluid filters. Is there a source for replacement micronic filters?

Brian
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[Jim B]

There is one filter used, located in the reservoir. Two different length filter were used. You will need to open the hydraulic reservoir and see which filter you need. Different hardware is needed for each filter. The hardware can be changed so either filter could be used. I believe you will find it is a screen type which you can clean and reuse. John Deere may be your only source for them.

[briancady413]

Jim B, indeed I had the wrong serial #: actually it is
4E3D 069489 X
The sight L even now shows unmilky hydraulic fluid. Guess it was foamy.
I'm getting the micronic filter today.

[Jim B]

069489 is a 1968 serial number. They were built in Dubuque so it should be a T after the digits.

Have you inspected the filter in your reservoir? You need to know the length of the one in it to get a new one as at least the bolt that secures it is a different length for each one.

[briancady413]

Thank you, Jim B,

The filter is the 9.5" one, and has a big split along a seam, with stuff protruding. I ordered another from the local John Deere dealership.

Brian
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[Jim B]

Glad you have it coming.