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Mechanics Corner: When the pressure is on, are your couplers right?

Jim Schlund Published on 01 March 2010

If your implement isn’t working, some people want to unhook the coupler and work the remote levers under the implement housing while looking directly into it.

That is an absolute no-no. If the engine is running or if there is residual pressure, you can have 2,500 pounds of pressure in there, and if you slide that valve back that oil is going to spray right in your face. If that oil, which can get to be 200ºF and higher, gets in your eyes, you will be blind.



I taught a class where I illustrated this point. I had a student stand next to the valve while the tractor was off and hold a big 5-gallon bucket up to the connection port. When I opened the remote valve hookup lever, the oil, which was under residual pressure, shot the bucket out of the student’s hands and across the shop. That was an eye-opening experience for them.

Some operators, especially young people, don’t understand the danger. They get frustrated that they can’t get the coupler on or it’s stuck, and they might do something that could really harm them. If the implement is running the damage can be even worse than just blinding yourself. If it’s not running properly, never take off the hoses or couplers without relieving the pressure and turning off the machine. People have been blinded by not following that simple guideline. A lot of guys who farm say, “It hasn’t happened to me,” but there is a good chance you can get hurt.

Any time you disconnect a line or fitting, you must relieve the pressure. The way you do that is to work the auxiliary levers after the machine is turned off. Then when you pull the implement off, make sure you don’t have it aimed at your face or body. Safety glasses are a good idea, even if you are careful.

Sometimes when people go to hook up an implement, they say, “I can’t hook this up. It won’t go in.” That’s because there is still too much pressure against that cylinder. The pressure can be caused by implements being left up, temperatures fluctuating a lot or something along those lines keeping the ball from unseating. There is another ball on the other side of the connection and when the coupler is firmly in place the two balls will unseat each other and allow oil to pass through there.

When the pressure is too high for any reason, it’s really hard to get it to connect properly. Some farmers will solve this problem by smacking the end of the coupler against something hard, releasing the pressure.


What they don’t realize is that the ball is chrome-plated, and when they smack that ball against something hard, it creates an indentation, mark or crack on the ball. So then they put it back in and the hydraulic oil starts working on that crack and it gets under that chrome plating. Eventually it starts to take that chrome shell off of the steel ball. Those chrome pieces get in those lines, they get in the cylinders, back in the system, and that’s what can start some real problems. It usually starts right at the coupler.

If you forget to release the pressure before disconnecting the implement, try this. Instead of hitting the coupler on something that might damage it, you need to safely relieve the high pressure by working the remote in the cab. Or if that doesn’t fix it, standing clear of the implement, use pliers to slowly disconnect the coupler. Take safety precautions, so the implement or potentially hot oil won’t injure you.

If you ever run into a coupler problem, whether it’s the wrong coupler or there’s something wrong with the coupler or you have the wrong ends on it, the problem seems bigger than it really is. What will happen is the operator will go to lift the bucket or implement and it won’t go up all the way. It will go up to a certain point and then stop, kicking the lever off. Then the operator will lower it and try to put it back up and it will stop again – it won’t cycle all the way. What’s happening is that coupler has something in there or isn’t the right size or type, and it’s not letting the oil get through. You can spend a lot of money, thinking it’s a serious problem, but it might just be something in the coupler or a bad coupler. The key is this: Any time you see the shell of the ball in a coupler is damaged or cracked, get it off there. Don’t leave it on. You wouldn’t think that it’s that big of a problem, but it can cause lots of damage and frustration.

Also, during the winter, you need to cover your couplers so they don’t rust and get dirt in them.


When hooking up couplers, you will want to make sure your hoses are connected right. I always paint the end of the left hose yellow. I never have to guess which one goes on the left and right. PD


Remember to send any equipment questions you have for Jim to editor

Jim Schlund
  • Jim Schlund

  • Retired Diesel
  • Mechanics Professor
  • College of Southern Idaho