Loader F6640 Loader Problem

Jackfr · May 22, 2010

Our F6640 with a 7411 loader is having problems. The loader will lift when empty but has a hard time with a full bucket. The bucket curls ok under load but when lifting under load there is a hissing sound coming from the spool valve like something is bypassing and the loader lifts real slow almost stalls. My guess its a relief valve stuck open but where. I've looked in the loader manual and found nothing except it says to check the relief valve in the troubleshooting chart. Anyone have an ideas where and what to look for? Rick do you have one of your quick easy fixes??

Jack

RickB · May 23, 2010

Check the pressure at all the loader hose couplers by removing the hoses and plugging in a gauge with a 5000 psi scale. Check and record the pressure at all 4 couplers at a given moderate RPM with tractor warmed up.

Jackfr · May 23, 2010

thanks Rick I'll hopefully be able to try that test later today when a friend brings some fittings so I can attach the guage to the valve. Makes sense with everthing i have here always the one thing you need on a Sunday you don't have! The latest will be tomorro.

On another note I tried the loader again this morning and while checking to make sure none of the four remote valves were stuck on I noticed if you dead head one of the remote valves the loader works fine! plenty of speed and power both in curl and lift. Could this problem be that proportioning valve again and not the spool valve? I can still hear the hissing noise but the loader works fine, actually better than it has in a long while as long as I keep the reomte valve dead headed.

Jack

Jackfr · May 24, 2010

Checked the pressure at all four ports using quick disconnect connection and 5000psi guage. Engine and oil warm 1500 rpm. Hoist was 1650 psi, Curl was 1600 psi, Lower was 2200 psi and dump was 2100 psi. All ports read 2500 psi when dead heading one of the rear remotes. I noticed a decrease/increase in pressure as I released/turned on each port. Did not reach full pressure if I feathered the valve. Could the pressure differences be because of a worn joystick and linkage as this one is pretty worn.

On another note while coming in yesterday from a rear field a drive train noise developed in this tractor like something was floating around in a case but only while I was moving. It sounded like a drive shaft flipping around but everything still seems to work? I'll start a new thread when I have a chance to investigate this problem further. Will have help later today so maybe I can jack it up and try and find the source of the noise. For now it's parked so hopefully I can get this hydraulic problem fixed.

When it rains it pours.

Jack

RickB · May 24, 2010

Tell me how your loader control valve is connected to the tractor's hydraulic system. Also refresh my memory as to which transmission you have, and/or whether the tractor is an S, SL, or SLE model.

Jackfr · May 24, 2010

Its t'd into the steel supply line that runs between the proportioning valve and the rear remotes. The sensing line goes into one of the remotes and the sensing lines for the remotes are t's together and then to the proportioning valve.
The Transmission is a 12 speed with a syncro reverser (which the syncros are on their way out and the linkage is badly worn) and the tractor is a SL model.
I didn't have time to check into the drive train noise further today other than lifting the front end with the bucket, starting it so it would come out of 4 wheel drive and then spinning the front end by hand no noise. I haven't tried to move it since I parked it yesterday.

RickB · May 25, 2010

Look for debris or other type of failure in the check valves in the signal line coming from the rear remotes. Signal flow has to be prevented from backflowing into unused valves, and it seems yours is not. Your description suggests the leakoff of signal pressure & flow is only stopped when you deadhead an unused remote valve while using a loader function.

Jackfr · May 26, 2010

The signal line is plumbed from the loader spool valve to a port on the top right remote bank of 2 remotes. The line then comes back out another port of the right top remote bank and t's one line to a port on the left bank of 2 remotes the other to the proportioning valve. It looks the way it's plumbed that both double banks of remotes and the loader are all T'd into this signal line. So anyone could request more flow/pressure. I looked in the books and could not find where the check valves would be. How does the signal flow work? When I dead head anyone of the remotes does it send increased pressure to the proportioning valve causing it to flow more oil and pressure to all the remotes including the loader as they are all t'd together on the pressure supply side also?

On another note we looked at the drive train last night and no noise in drive train, took it out and drove it no noise ! I don't understand this. I know what I heard on Sunday. Could sloppy linkage cause gears to partially engage when you hit a bump? Both the Syncro reverser and gear shift linkages are worn real bad and the reverse syncro is no longer there. I'm going to try using it today for disking as we need to get this two acre piece planted it's getting real late for grass.

RickB · May 26, 2010

Any valve when stroked creates pressure and flow in the signal line along with pressure and flow in the work port(s) connected to the valve. There is a check valve associated with the signal circuit FOR EVERY VALVE SPOOL to prevent signal flow from a valve in use from being returned to sump through a valve that is not in use. In theory, you could connect the signal line coming from the loader control valve directly to the porportioning valve. If the loader reacts properly, you could connect the remotes and see which if any remote valves are bleeding off the signal flow.

In general, the 'Tee" fittings in the signal lines contain the check balls.

Jackfr · Jun 1, 2010

Sorry it took so long to reply but we've been planting a new section of field and just finished last night. During the weekend someone suggested we try adjusting the cables to the joystick. We tried lengthening the linkage cables at the joystick as there is a lot of "slop" in the joystick. The curl now works fine and when it dead heads at the end of it's stroke it causes the hoist to work. Changing the length on the hoist cable made no difference except to eliminate the float position. I'll reset that later today. I'll also retest the pressures later today and get back to you. I haven't had time to get into checking for debris in the signal lines yet but if the curl now sends signal to increase pressure they should be ok right? Is there some way to adjust spool loader spool valve section internally so it will it will work properly?

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.