Loader F6640 Loader Problem

[Jackfr]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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?