# Air in lift cylinder



## yankeezulu123 (Feb 27, 2011)

I have an 8' 2007, Boss RT3, Straight Blade. This is my first plow. 

About a month ago over a period of two days I noticed that my plow seemed to not raise as far as it had since the start of the winter. I had about 2 – 3” of lift left in the cylinder that wasn't retracting.

I lower the plow to float each time I park. The next morning I came outside and the plow would not raise at all. I checked the fluid level, as I do multiple times a day now, and it was where it should be in the elbow. I had air in the lift cylinder and loosened the screw and bled it out. That got the plow lifting again to max height, cylinder totally retracted.

Throughout the day the plow again stopped lifting completely. 

I checked both lift and lower coils. Had magnetism. I removed both valves and replaced the lift just to be certain while I already had it out. I removed the pressure valve. Inspected it and it looked normal. Nothing that would make me think it was bad. After reinstalling the valve I turned the pressure up two full turns. I have no pressure gauge, and I can't find a store in my area that carries one. Haven't gotten around to ordering one. 

Bled air from the lift cylinder again and plow raised fully, cylinder totally retracted.

The past four or five times plowing, over the course of a solid 8 hour day, I have to bleed the air from the lift cylinder about 4 times. It takes about 2 hours for my plow to go from full lift, to scraping the ground. 

I have no problems with the speed of lowering, no angle problems. Nothing. It is just lift, and having air in the cylinder.

Ive also noticed small drips of fluid on driveways. I wasn't sure if the plow was leaking from somewhere, or if it was just fluid from bleeding the cylinder, running back down through the tower, etc.

Last week I got the truck in my garage and double checked everything. I took out the valves that I had removed originally. Reinstalled them tight. Checked all the hoses. Checked the seal on the lift cylinder. Checked every cap and screw and ensured they were all tight. I filled the reservoir itself through the main top port. It had slightly more fluid than it should. Bled the air off the cylinder again. Cleaned everything real well to remove fluid residue from bleeding the cylinder, which does run down into the manifold / motor / reservoir compartment. 

Then I had my girlfriend run the controller while I had my head in the tower. No leaks from any of the valves, hoses, or the cylinder. 

When she pushed down on the controller and set the plow onto the floor in full FLOAT, fluid would come out the top port / cap on the reservoir. I removed the pressure valve cap and slowly turned pressure back until no fluid was coming out the cap.

I again cleaned everything off, and watched again while she worked the plow. No fluid leaks from anywhere.

Yesterday I took the plow out, and same thing again – plow not totally lifting over the course of a day. Slowly losing lift. Having to stop every two hours to bleed air out of the lift cylinder before the plow starts scraping the ground.

I did talk to my local shop, and he said with all that all he can think of is maybe my packing nut on the lift cylinder is a little loose. I tried to tighten where he described to me (collar where the piston goes into the cylinder) but even with a big pipe wrench can't get it to move at all, let alone turn 1/4 turn.

I'm also burning through fluid even though I can't find any leaks. About 1.5 qts in 8 hours. I'm not sure if its from bleeding off the lift cylinder or if I'm just missing something.

I can't find anything online or anyone in person that can address this issue. I've checked the boss troubleshooting guide. Talked to my local shop. I'm not half bad mechanically and own a few tractors with hydraulics that I work on and never have an issue. 

Can anyone give me some advice?


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## yankeezulu123 (Feb 27, 2011)

And I don't "Plow Reckless" like in the Boss Trouble Shooting Guide. I even tried being ridiculously careful pushing into piles, stacking snow, anything stressful on the plow, and its the same issue no matter how much I baby it.


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## Omran (Oct 10, 2009)

did you get the plow brand new? if so Boss have to help you fixing it, may be the whole cylender need to be replaced. or just thinking, may be one of the hoses has very tiny hole in it. soory I am not that good of help, but that somthing came to my mind.


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## jklawn&Plow (Jan 8, 2011)

I don't know but if your loosing that much fluid, there must be a leak somewhere, but how to find it. It could be letting air in also. I overfilled my reservoir and it leaks out the top cap occasionally- still above lower level of side port after two years. If you could wrap a white cloth aroung some key connections and verify no red fluid leaking there and narrow it down. Sorry no clue


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## no lead (Dec 10, 2008)

just for kicks try this. put a floor jack under the plow and lift it until the cylinder is retracted all the way. push up on the control and make sure it is all the way up. angle the plow left and right until it stops 10 times and keep holding the control for a few seconds each way. ( this won't hurt the plow). any oil leaks? now push lift again and remove the jack. go away and let the plow set in the up position for half an hour. now look and see if it has drifted down. if yes you have a problem in the valve or the cylinder. 

lift the plow again and put the jack under it. remove the hose from the lift cylinder and put a pipe plug in the cylinder. let the jack down and observe what happens. if the plow goes down the cylinder is bad. if the plow stays up you have debris in the valve.

stop trying to "bleed" the cylinder. your just letting air in. put the plow down and fill it with oil. angle the plow 10 times while it is down. fill it with oil. angle 10 times again leaving the plow down. is it full? when you lift the plow oil should not come out of the vent cap. if it does the cylinder is bad.

assuming the plow is not purging oil from the vent cap put the plow in the up position. take a cardboard box and collapse it under the plow. leave the plow up and go to bed. in the morning if the plow is leaking it will show an oil spot on the cardboard.

sorry for the long post but this is what i would do.


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