John Deere 300 Industrial hydraulic problems

[JD300]

I have a 70's John Deere 300 Industrial tractor/loader (similar to a 1020) with a JD9250 backhoe attachment which has served me well for 15 years of occasional use. Recently, it has developed a hydraulic problem. First, after using it for hours, suddenly the loader and backhoe would not operate at all. Engine runs fine, transmission fine, tractor moves fine. No funny noises, just nothing. After about 10 minutes, hydraulic function came back, then came and went intermittently.

The next day, tractor ran fine for about 30 minutes, then the same intermittent loss of hydraulics. Next day, same thing. Oil level is fine.

I thought it might be clogged filters, so I changed both hydraulic filters (the transmission one and the loader return one. I also changed the hyd. fluid. The oil fluid and filters were clean as new. So I started it up, let it idle to self-purge for about 20 minutes, and it operated fine for about 5 minutes then, intermittently began to lose hydraulics, with occasional shuddering and air banging around in the lines. No amount to extending/retracting of the cylinders would clear them out. I have changed fluids on this tractor before and never had this problem. It feels like air is being sucked into the lines somewhere, but hoses and lines look tight.

I am not very familiar with hydraulics and would be grateful for a point in the right direction to troubleshoot this problem.

Many thanks,
Richard

 

[kennyd]

Welcome to TBN

Two things come to mind...A leak on the SUCTION side of the pump causing the pump to suck air and cavitate, or the pump is just plian shot and when it warms up will not build pressure.

 

[Wayne County Hose]

Welcome to TBN. I'll bet you wish that you could have come here in a better situation. The only thing that makes me doubt a suction problem is that it comes and goes all of the sudden intermittently. Am I correct in this assumption? I would check the pump coupler. Or, start up and run, run one of the cylinders to full extension or retraction and hold the valve for a couple seconds, making the pump really work. Any strange noises you never heard before? This also checks the pump coupler, kinda. Or, a bad pump like Kenny said.

 

[kennyd]

Good thought on the coupler Andy, I forgot the older machines use a external pump driven through a Lovejoy or similar coupler. I am used to the newer machines...

 

[JD300]

Many thanks for the quick responses!

Sometimes the machine runs normally. It has plenty of hydraulic power, plenty of bucket lift. It can easily lift the tractor with down pressure with either the front loader or backhoe. It can run this way for minutes. When it is running normally, it sounds normal. This makes me think the pump is okay.

Then, suddenly, no pressure. If a bucket happens to be up, it stays up until you put it down. Then nothing. At this point, it still sounds normal, no click-click-click like it is out of oil. If you hold a valve open, no pressure, no funny noises. It can be like this for minutes at a time. RPM doesn't help. Then, sometimes, the cylinder will start to move, slowly as it builds up pressure. Sometimes the whole tractor will shutter loudly as the cylinder ratchets up. You can hear air pinging around in the lines. Sometimes, after shuddering for a few seconds, the pump will "catch" and pressure and operation will be normal for a minuter, or so. Then, it goes off-line again.

The problem seems to more related to the loader than the backhoe. In fact, when the loader cylinders are "dead", if you open the backhoe valves and move the backhoe pistons a bit, you can restore pressure to the loader for a while. The tractor itself always has moved forward and back on its own.

It does seem like an air suction problem, but I am not sure.
Richard

 

[Wayne County Hose]

Good thought on the coupler Andy, I forgot the older machines use a external pump driven through a Lovejoy or similar coupler. I am used to the newer machines...

....And I am used to the older stuff. I can't afford newer.

This does sound like either a pump or something on the suction side, as Kenny has said. Almost sounds like cavitation. I doubt that the pump coupler is the culprit. You better fix it soon before your pump grenades.

 

[true temper]

Did you get your 300 fixed? How about the power steering, is it working? If it is working your priority valve is stuck. The valve is located on the side of transmission above the filter housing. If there is a problem with it the back hoe and steering will work but not the loader.

 

[Rara Avis]

Many thanks for the quick responses!

Sometimes the machine runs normally. It has plenty of hydraulic power, plenty of bucket lift. It can easily lift the tractor with down pressure with either the front loader or backhoe. It can run this way for minutes. When it is running normally, it sounds normal. This makes me think the pump is okay.

Then, suddenly, no pressure. If a bucket happens to be up, it stays up until you put it down. Then nothing. At this point, it still sounds normal, no click-click-click like it is out of oil. If you hold a valve open, no pressure, no funny noises. It can be like this for minutes at a time. RPM doesn't help. Then, sometimes, the cylinder will start to move, slowly as it builds up pressure. Sometimes the whole tractor will shutter loudly as the cylinder ratchets up. You can hear air pinging around in the lines. Sometimes, after shuddering for a few seconds, the pump will "catch" and pressure and operation will be normal for a minuter, or so. Then, it goes off-line again.

The problem seems to more related to the loader than the backhoe. In fact, when the loader cylinders are "dead", if you open the backhoe valves and move the backhoe pistons a bit, you can restore pressure to the loader for a while. The tractor itself always has moved forward and back on its own.

It does seem like an air suction problem, but I am not sure.
Richard

NO Hydraulic Functions
1. Check hydraulic oil level, type and viscosity.
2. Check suction line for air leaks.
3. Hydraulic pump seals leaking including pump shaft seal.
4. Check for plugged reservior screen and vent.
5. Check for damaged or missing pump coupler.
6. Hydraulic pump damaged(scored or worn)
7. System relief valve stuck open.
8. Cracked flow divider housing.

 

[JD300]

<<<<Did you get your 300 fixed? How about the power steering, is it working? If it is working your priority valve is stuck. The valve is located on the side of transmission above the filter housing. If there is a problem with it the back hoe and steering will work but not the loader.>>>

Not yet! The tractor is about 100 miles from my house. I'll have another crack at it this weekend. When the hydraulics go offline, I am pretty sure the power steering is dead too. Also, when the loader dies, the backhoe cylinders are dead too. Where is the priority valve? My parts book does not show it.

Two possibilities, both on the right side of the transmission case above the loader return oil filter:

1. a part bolted to the side of the transmission case with about 4 oil lines going to it, and with a relief valve, or

2. A plug by the floorboard, by your right heel, on the side of the transmission case. My parts book shows a spring behind this, like it is some type of pressure valve, but the parts inside are stuck in when I removed the outside plug.

I appreciate your help. I am lost without my handy little backhoe!

 

[JD300]

<<<<<NO Hydraulic Functions
1. Check hydraulic oil level, type and viscosity.
2. Check suction line for air leaks.
3. Hydraulic pump seals leaking including pump shaft seal.
4. Check for plugged reservior screen and vent.
5. Check for damaged or missing pump coupler.
6. Hydraulic pump damaged(scored or worn)
7. System relief valve stuck open.
8. Cracked flow divider housing.
__________________
Paul in VT>>>>>>

Where is the System relief valve located? There are several plugs on the transmission and oil filters which have spring-loaded valves behind them. Also, there is a plug by the floorboard, by your right heel, on the right side of the transmission case. My parts book shows a spring and some other parts behind this, like it is some type of pressure valve, but the parts inside are stuck in when I removed the outside plug. Is this the system relief valve?

Many thanks!