2640 hydraulic problem

[48powerblockA]

Hi, I purchased a 2640 this spring with a 146 loader on it. Everything worked fine up until lately if you are idling the tractor and pull either loader control handle, or try steering it's like there is no hydraulics.Once you Rev it up for a few seconds everything works properly. I replaced the hydraulic filter, as well as the sump screen and put in new oil. Still does the same thing. I just ordered a repair manual, but was just wondering if anyone out there has any thoughts. Thanks!

 

[Tx Jim]

With 3 pt raised,engine running look in hyd filler hole behind seat for spraying oil. What type valve controls FEL(ind spools or scv)? Does tractor have hyd ind pto or hyd hi-lo?

 

[48powerblockA]

It has independent spools for the FEL. It does have a hyd. Hi-lo as well. I will try running it this evening and take a look in the filler hole.

 

[Tx Jim]

Try operating hyd's with hyd hi-lo in both speeds. It's possible if spool valve is the convertible type(open-center to closed-center/vice verse) that seal has blown on conversion plug letting valve revert back to open-center. To check for blown seal in valve disconnect valve return hose from tractor & with both spools in neutral with engine running no oil should exit open return hose.

 

[buickanddeere]

Where is he two spool valve set plumbed into the tractor for supply and where does the loader oil return in to the tractor? Is there a relief valve in the loader control valves? Is the power steering hot and noisy? Any difference to the loader with the pto running or off?

 

[MrSykes]

I have the same JD 2640 tractor (mfg 1982 and 6000hrs) with Hi/Low and 146 loader (ported oil filter housing) and have the same problem so I'll be very curious to know what you find. Maybe we can compare notes. I do have the JD service manual if you need any info. The manual has a section devoted to hydraulic troubleshooting but I've not had a chance to really dig into it. I've changed the fluid (Hy-Gard), filter and cleaned the screen without any change. (There was a little bit of red brake pad material but the screen was not clogged) Mine seems to get a bit worse when it gets fully warmed up. FWIW, I did look in the fill hole and didn't see any spray. The RS works fine without any noticeable chatter. It's just the steering that occasionally locks for a second at lower rpm and the loader shudders at any rpm. Increasing rpm only seems to make the loader shudder/chatter faster (I'm guessing pump strokes). The loader is fairly smooth if I slowly raise it. I read somewhere that slightly overfilling the sump helps but I tried adding an extra gallon and it didn't make any difference. Even if the low pressure pump were weak or there was a broken/cracked pipe to the main pump, according to the manual the aux tank on top of the main pump should fill up between uses and supply oil to the main pump if the inlet pressure drops. I think I need to make sure that the check valve on the aux tank is not stuck closed. Sorry so long but maybe together we can figure this out.

 

[Tx Jim]

Check hyd filter relief valve(parts keeys 7 & 9) to be sure it's not stuck open.

 

[MrSykes]

I'll do that and let you know what I find. Thanks.

 

[MrSykes]

I checked the filter bypass valve and it's not stuck open. It takes about 10 lbs to fully compress to the bypass position and seems smooth with no debris. I checked the filter screen and it did have some friction material (thin material, red color on one side and black on the other) but it was limited to the far end of the screen and did not appear to block much area. I removed the plugs from both ends of the screen slot, cleaned the screen and ran rolled up paper towels through the case until no more material came out. Should I pull the pressure regulator valve off and inspect it next?

FYI, I've attached a link to a video that shows what it looks like with the fill cap off while running. There's fog but I'm not sure if it indicates a problem or is normal.
jd2640_fog

 

[MrSykes]

Does anyone know if the fog/mist shown in the video above is an indication of a problem? I'm not sure if this is what people mean when they're referring to fluid spraying around in the RS housing. For all I know this could be normal.

 

[Tx Jim]

Was hyd oil at operating temp??? JD utility tractors of that era have rockshaft control valves with a long history of leaking. I think the fog in your video indicates leaking of these valves or possibly scv valves leaking if so equipped. You could remove rubber hose between scv & RS housing to eliminate if scv valve is leaking.