Go BottomJerky Fel main boom
 | tracer
Join Date: Jul 2003 Posts: 49 boyce Va 
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2004-05-24 86711
Help
I was moving some dirt with my 419 FEL on my 2002 790 with 110 hours and right afterwards the main booms are severely erratic moving up. The Bucket dump moves up and down ok and the main booms will drop ok but on the upward move it jerks badly. The fluid level is ok and the only other advice the manual gives is " See Dealer". Did I break it? Any Ideas?
Tracer
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 | beagle
Join Date: Jan 2004 Posts: 1333 Michigan 
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2004-05-24 86717
Broken is a relative concept. You may have one of two problems. Air in the hydraulic system from a loose fitting on the suction side of the system, or a mal-functioning pressure relief valve on the loader. Cycle the system several times to relieve any air, and check for any hydraulic leaks on the suction side. If you aren't used to working on hydraulic systems, it may be best to have the dealer check out the pressure relief. Hydraulic fluid under pressure can cause serious injury and infection. ....
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 | DRankin
Join Date: Jan 2000 Posts: 5116 Northern Nevada 
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2004-05-24 86724
Sounds like a loose quik-connect could be causing the problem. Check that they are all clicked together correctly and the backing plate nuts are firmed up. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-05-25 86776
Sounds like it may still be under warranty and letting the dealer fix it would be the easiest. If the loader was used like a dozer with the blade angled down when it happened that might have damaged it and the warranty coverage might be shakey. However, the bucket circuit rather than lift would be more likely damaged.
For a do it yourself, I'd start by changing the filter if it hasn't been done. Then I'd jiggle the joystick to ensure both valves are centered and then try to lift the wheels with the bucket curl. If it does that normally then the pump/relief valve is probably OK and the problem is in the lift valve or cylinders. You could swap the lift and bucket cylinder lines to test the valve. If the lift problem stops and the bucket becomes jerky then the valve is likely the problem. If it doesn't stop then the cylinders are likely the problem. ....
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 | Murf
Join Date: Dec 1999 Posts: 7249 Toronto Area, Ontario, Canada
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2004-05-25 86780
When you said it was right after moving some dirt you gave it away.
There is air in the FEL cyliders. This air did not likely get in there fro any loose fittings or connectors, it came from the reservior and was caused by the weight of the dirt itself.
It is called 'load-induced cavitation'.
It works like this, when the FEL is under load the hyd. fluid in the cylinders is under pressure from the load pushing down. If the pump output is below the volume needed to fill the 'back side' of the cylinder and generated by the load pushing down when the load is dumped it will result in a vacuum in the line. This results in air being sucked up the pickup line since air moves easier than oil.
The problem appears the next time you try to lift the FEL, the pressure causes the air to compress until it reaches pressures high enough to make the boom move up, then it springs up and bounces a little from the sponginess of the air, then it pauses until pressures rise again.
The cure is simple, just rev. the engine up and cycle the fEL through the full range of its motion a few times to purge all the air back into reservoir.
To prevent re-occurence either keep the engine speed up and dump slowly, or install a "line throttle valve" on the offending line. These are simple little devices that limit the flow of oil in one direction but not the other. You install it such that oil can only escape at a slower rate, but it gets full flow to work the cylinder. They are cheap and super simple to install.
Best of luck. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-05-26 86889
Oh yeah I jumped directly to trouble shooting. Cycling the loader before thinking about fixing it always is better. Running at substantial rpm when doing heavy work also is good.
Sure hope cavitation is the answer, although I usually associate it more with the bucket than the lift circuit--the large side of the cylinders is on the pressure side for dumping and the small side is on pressure side for lowering. Some of the cavitation vapour also is reabsorbed after the vacuum is resolved as well. ....
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| tracer
Join Date: Jul 2003 Posts: 49 boyce Va
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2004-05-28 87090
Slight Disaster;
Greetings All,
Thanks for the advice but nothing has worked. When I went back the bucket also became "Jerky". The fluid level was a little low so I added some clear Hy-Guard but I over filled it. When attempting to Drain a "little bit" out, the drain plug fell into the funnel I was trying to use to catch the fluid into a clean Two gallon container. I did not realize this until after a frantic search- ever try to stop tranny fluid from flowing while looking for a drain plug that you "KNOW" fell into the catch basin? Well my arms and gloves got wet as did the ground as did my back cause I was laying in it and I didnt even cuss that much!:)
There does seem to be a leak from the one inch return hose behind the filter, possibly the original problem but at this point I have decided discretion is the better part of valor and called the dealer. He is coming out on Tuesday. I will keep you informed. Again thaks for the advice.
Tracer ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-05-29 87151
Sorry about the mess. Screwing the filler cap back in would have helped slow the flow until the plug was found. Hope it wasn't too bad a clean up.
It sounds like both circuits are affected and that there's a leak in the suction hose. Such a leak could sure cause the cavitation symptoms Murf mentioned. Bad luck the problem was noticed while performing heavy work and that it affected both circuits or the original thinking may have been different. ....
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| tracer
Join Date: Jul 2003 Posts: 49 boyce Va
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2004-06-01 87453
Getting Worse
Greetings all,
Well things have gone from bad to more bad. Now the booms will not move at all unless I hold the joystick in position for 5 to 10 seconds and the power steering is going too. Can a leak in The return hose behind the filter cause the system to do this? Seems pretty severe. The 3 point also is slow but I do not detect a major leak " oil on the floor". The Dealer just picked it up today so we $hall $ee what the damage i$. Ill keep you informed. Again Thanks. Tracer ....
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| Murf
Join Date: Dec 1999 Posts: 7249 Toronto Area, Ontario, Canada
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2004-06-02 87501
Tracer, yes air in the system will do exactly what you describe, and yes even a minute leak in the return line can cause a LOT of air to enter the system.
The good news is that something like that is usually a quick & (relatively) inexpensive repair. If you took it to the dealer he will certainly use factory parts, they can be a lot more money than the equivalent non-OEM part but that's the case with anything.
Best of luck. ....
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| tracer
Join Date: Jul 2003 Posts: 49 boyce Va
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2004-06-03 87670
Hoser
Greetings all
Dealer called and said the hose was the problem. I did not realize the hose was actually pulled off enough to cause the problem. The hose should be 4 to five inches over the fitting and it was just barely hanging on and letting lots of air in causing the problem. Boy do I feel stupid. Well at least it is not an expensive learning experience. The tractor comes home from the hospital err dealership tomorrow and I will spend some time inspecting hoses and clamps so I know what is supposed to look like what. I was a little timid with the hose inspection but I did not want to pull the thing off and get a tranny fluid bath but I did anyway-see above. This really is like ZEN and Motorcycle maintenance isnt it? I need to have more faith in my instincts but at the same time caution is a good thing too. Stll living and learning at 49. Speaking of Motorcycles does anyone have aninterest in a 1975 XS 650 Yammer. It runs but needs a tune. Thanks to all.
Tracer ....
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| tracer
Join Date: Jul 2003 Posts: 49 boyce Va
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2004-06-04 87748
Greetings
If anyone is still reading this thread here is the follow up. $146.51 , 100 for pickup and rtn mileage. 35 for labor and 10 for some tranny fluid. Everything works. Hose actually looks new as does clamp. Thanks for all the input, it really does help.
Sincerely
Tracer ....
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