Loader F6640 Loader Problem

Jackfr · Jun 2, 2010

Checked pressures again this morning. Checked the pressure at all four ports again using quick disconnect connection and 5000 psi guage. Engine oil and hydraulic oil warm 1500 rpm. Hoist was 1650 psi(No change), Curl was 2500 psi(changed), Lower was 2200 psi(No Float position)and dump was 2500 psi(changed). If I operated the curl or dump at the same time(dead head as nothing is hooked up to them) the hoist and lower go to 2500 psi. The changes happened after adjusting linkage. So it looks like a problem in the loader spool valve along with the sloppy joystick. Appears I can get a rebuild kit for the joystick for $94. But what do I look to repair in the spool valve Rick? I haven't readjusted the joystick to get back float yet. I'll probably order rebuild kit for it and then readjust it. I'll wait to hear back from you.

Couple of local mechanics suggested I buy an after market Joystick/spool valve combination instead of trying to repair the NH setup. Somewhere around $400 after hoses they tell me, but I haven't been able to find one with a signal line output yet. Suggestions anyone?? The New NH valve is $1530. Unless I can get the right rebuild kits for it and I can get it to work again

RickB · Jun 2, 2010

Rebuilding a spool valve with internal leakage is tricky because most of the actual internal sealing involves close tolerances between the spool and valve body. There is no rebuilding that. The advise to replace the entire valve/joystick combination is worth looking into to the extent you can put a finite cost to eliminating your problem.

Jackfr · Jun 2, 2010

Rick what should I be looking for. I know probably 3000 psi but what gallon flow and what about the signal circuit flow/pressure any suggestions?

Jackfr · Jun 8, 2010

Does anyone know what the signal/pilot pressure should be on this machine? I found out that the gpm is around 8.9 gpm and working pressure on the main lines is around 2500psi. It "appears" that the signal/pilot line pressure is the same as the working pressure from the drawings but no where does it say what it is in my service manuals. I need to know in order to order new spool valve as this pressure is set at the factory and not field changable.

Jackfr · Jul 9, 2010

We are finally catching up with spring planting chores and have had time to check a few more things. I disconnected the linkage and operated the spool valve directly at the valve to make sure I was getting full travel because of the worn linkage. This made no difference in the loader operation. I checked the signal line pressures from the rear remotes to the proportioning valve and the pressure is 2550 psi but the pressure on the signal line from the spool valve is only around 1600 psi unless you deadhead a remote at the same time as using the loader spool valve then the pressure jumps to the 2550. I checked the check valves as RickB suggested and they appear to be clean and working properly. There is a "hissing" noise when hoisting or curling the bucket coming from the spool valve like you were feathering the valve. So far everything points to the signal from spool valve being the problem as the loader will work fine with plenty of power if you keep a remote deadheaded. That's how we've been using it (hopefully not causing further problems). I have the service manuals for this tractor but don't have any experience in taking apart/rebuilding spool valves. The online NH parts manual lists numerous kits for rebuilding this spool valve, not sure which ones I need. Anyone with suggestions before I jump into this? To replace the linkage and spool valve from NH the parts are close to $3000. Does anyone know where I might buy an after market spool valve joystick combination with a signal line port I have had no luck in finding one or should I try taking this valve out and try rebuilding it. I started anothe thread under Hydraulics hoping for more input Loader Hydraulic Problem - TractorByNet.com

Jackfr · Jul 25, 2010

The hisssing sound from the loader spool vslve is getting louder. We finially bought some adapters and did the last test RickB suggested.

RickB said:
In theory, you could connect the signal line coming from the loader control valve directly to the porportioning valve.

Same readings as in the past with just the loader hooked up. So it looks like it's in the loader vavle.

I have talked to 2 hydraulic repair shops and they both are leaning to a damaged spool valve section and possible two, probably a crack in one if not both sections. So with repair kits and labor the cost is getting close to a new valve without replacing a spool section. I have not been able to find an aftermarket valve with the right specs.

We ordered a new valve from our NH dealer and a new joystick Assembly. Hopefully this will take care of this long ongoing problem. Parts should be here the end of the week. I'll keep you posted

Jackfr · Aug 1, 2010

New valve and Joystick assembly arrived. We finished R&R it yesterday it was not a "five minute job". Started late afternoon Friday quit around 9 pm and finially finished around noon Saturday. Hardest part was connecting cables to the valve spools. Everything is working fine now including higher pressure readings at all outlets including rear remotes. Everything reads approx 2800 psi. So I must of had a bad internal leak in the loader spool valve.

I was curious so I took the old valve apart this morning. No bulging or broken orings, the hoist/float spool had some scratches in it but nothing major It only had one load check (item 11) in it though not the two it shows in the parts diagram on Messicks site New Holland 7411-SERIES QUICK ATTACH FARM LOADERS (017 control valve)nor does it have the bleed off plug Item 58. I could see no cracks anywhere in any of the sections, no broken springs or other missing parts. Maybe a hairline crack that I can't see and only opens under pressure or spools worn so they leak by? I don't know what caused the problem in the first place which bothers me. Any Ideas?

Bottom line is, it is working fine now thanks to all who helped along the way.

We think we might of found a crack inside a galley of the old spool valve. I thought at first it was a casting mark but on closer inspection I think it might be a crack. Here are some pictures of it.