Pressure on quick connects

[Woody65]

I just recently purchased a 2005 Bobcat 331 excavator. I purchased a thumb to attach to it and after getting all the hard stuff accomplished I went to connect the quick couplers and had no problem with the male fitting but cannot get the female coupler from the thumb to connect to the excavators male connect. I tried disconnecting the lines from the thumbs hyd cylinder, moved all of the joysticks and hyd levers around after shut down to try and release the back pressure to no avail. I can connect the two hoses from the thumb cylinder together. When I try to push it on it gets about 3/4 the way on and I run into back pressure. I am pushing so hard that the boom arm and dipper are moving back and forth. Any suggestions?

 

[ovrszd]

Are you saying with the hoses disconnected from the thumb cylinder it still won't couple?? If so, would have to be in the connector somehow. Are you sure your couplers are the same type?? There are variations. And some of them will not mix. Uncouple everything and look at them carefully. That would explain why they will couple into each other but will not couple to your machine.

Let us know what you come up with. Got my curiosity up for sure.

Pics of the couplers would be nice too.

 

[crackerjack222]

Shut the machine down, move the hydraulic controls back and forth to relieve the pressure in the system. Use a wrench or other blunt metal object to press on the center of the connector. Have a rag wrapped around the connector to catch any oil that squirts out. Now you should be able to make the connection.

 

[DT86]

To me it sounds like it could be a bad fitting or still have pressure on the excavator side of the connection.
Are we talking about flat faced couplers?

 

[Woody65]

The couplers are the same because the male one connects to the female one on the excavator fine.

I did the shut down move all the joysticks around to no avail.

They are flat faced couplers.

I have heard of back pressure but this seems extreme.

 

[Bladehauler]

the skid steers have a pressure relief valve built in so on shut down you turn the key all the way to the left and hold it for a few seconds to drain all the pressure, I wonder if your 331 has the same setup ?

 

[Woody65]

My son in law just came over and between the two of us pulling and pushing it went on. We really had to monkey with it but once we got both of us on it the 450lbs won the battle. The thumb works great but I have to modify the bucket a little to get it to close all the way. So much for a pin on no welding required attachment. Thanks for all your suggestions.

 

[Woody65]

the skid steers have a pressure relief valve built in so on shut down you turn the key all the way to the left and hold it for a few seconds to drain all the pressure, I wonder if your 331 has the same setup ?

You must have posted while I was outside with my son in law. I will remember that for the next time. Thanks.

 

[Cord]

That machine has pilot controls so the circuit has to be energized to relieve the pressure. That said, I often have to crack a fitting to relieve the pressure. It doesn't seem to much pressure before you can't make the connection. Sun beating on the cylinder is enough. Sometimes you can try pulling on the attachment while a second person tries to make the attachment.

 

[ovrszd]

I thought the OP originally said he had removed the connections from the cylinder?? I must have misunderstood.

Next time, and there will be a next time, loosen the hose connection at the cylinder or loosen the coupler connection from the hose and relieve the pressure. The pressure problem was evidently in your thumb cylinder rather than the machine. Flat face couplers are harder to drain pressure off without doing damage to the coupler mechanism.

I learned long ago to uncouple hot, recouple cold.