Smallholders Insurance from Greenlands

Author Topic: Difficult hydraulic quick-connection-valve connections  (Read 716 times)


  • Joined Nov 2015
  • Kernow. Some say it's in England !
Difficult hydraulic quick-connection-valve connections
« on: July 09, 2018, 08:31:30 pm »
Supplier of my tractor has actually provided immediate solution for my subject problem, but I still have a residual quandary.

I have long had issues with connecting one of my side-shift flail mower's hyd' cylinder pipes to one of my tractor's quick connection valves (QCV) - the same one every time.  However, day before last, I just could not get the female/male connection to lock - no way!  Not being completely educated yet on tractor matters, I ordered a new female QCV, but supplier said "Whoa! - QCVs are very reliable and you probably have a pressure issue".  They were right.
Under instruction, I tried depressing the valve-head on the relevant male part (flail pipe) on a hard surface, suitably shrouded to prevent spurts of hyd' oil under pressure:  it wouldn't budge!  After unscrewing pipe connection to flail cylinder (again shrouded) to release pressure, the valve-head easily depressed and the flail pipe then connected to QCV just as it should.  So there has long been a pressure build-up issue despite fact that I always toggle hyd' levers to relieve pressure in tractor/implement hyd' circuit/s before disconnections.  I'm thinking it has to be due to temperatures and expansion of oil in flail cylinder (because I can't think of anything else).  Today, closed-up temp' inside tractor/flail "garage" (an ISO container) was 41C !!

Any other thoughts would be most welcome! 

Also, I can't be unscrewing hyd' cylinder connections every time the flail gets hot (if that is the problem): I tried re-toggling hyd' circuit levers with just one flail pipe connected to tractor with ignition off, but that didn't seem to help.  So, is it OK to just connect the other flail cylinder pipe and then, with tractor powered up, give the hydraulic lever a very, very, very brief flick to shift the cylinder piston by a fraction to relieve the pressure on the problematic side of the piston or will that cause problems of another kind?

[I hope that all makes sense from a "distance".]
« Last Edit: July 09, 2018, 08:41:11 pm by arobwk »


  • Joined Jan 2011
  • Dumfries & Galloway
Re: Difficult hydraulic quick-connection-valve connections
« Reply #1 on: July 10, 2018, 06:19:30 pm »
This happens with hydraulics , normally as you say when you switch the tractor off you wiggle the levers to release pressure or if necessary push or hit the male end ( on wood , metal can damage the end ) Can you switch off the tractor push the lever into release pressure then check the male end for pressure so ready for next time ??


  • Joined Nov 2015
  • Kernow. Some say it's in England !
Re: Difficult hydraulic quick-connection-valve connections
« Reply #2 on: July 10, 2018, 08:34:18 pm »
Thanks shep53;  I will do that at the next disconnection.  (Presently tractor/flail are paired-up ready to go and I may well leave them like that until I'm done with the delayed flailing!)
In passing & regarding quick connection valve plugs - I was grumbling about hard plastic QCV plugs (awful) versus soft rubbery QCV plugs (great) to my tractor supplier and they suggested Kramp flip caps as an option. 
I've never come across these before, but have now ordered some to replace the existing QCV plugs which all have broken restraining "tails". 
Here's the Kramp link that that my tractor supplier provided for anyone who might also be interested -
« Last Edit: July 11, 2018, 06:18:13 pm by arobwk »


  • Joined Nov 2015
  • Kernow. Some say it's in England !
Re: Difficult hydraulic quick-connection-valve connections
« Reply #3 on: July 11, 2018, 06:15:04 pm »
Further to:  I've been web-searching and also giving the issue some more thought.
Firstly, ambient temperature increase/oil expansion/pressure in disconnected implement cylinder is the problem.
Secondly, if the implement's cylinder rod is fully retracted (at storage) it is now obvious to me that there is no means of relieving a high pressure build-up in the implement's cylinder other than by undoing a pipe connection (or clouting the offending valve-end with a sledge hammer - obviously not recommended!!) on the end of the cylinder that is fully charged with oil.  However, I have found a solution ont' web (quite simple and obvious when one knows what the problem is!):
Store the implement with a "dummy" female quick connection valve (QCV) connected to a hyd' pipe male end on the implement.  (If the implement's piston rod is fully retracted, it would have to be connected to the cylinder/piston-end that is fully charged with oil!)  Any pressure build up will then be relieved through the dummy QCV and the web solution suggests pushing a tube/pipe onto the rear-end of the dummy QCV and fill the tube with a rag to absorb any expressed oil as ambient temperatures increase.
I'll caste around to see if I can scrounge a redundant, but working QCV.
« Last Edit: July 11, 2018, 06:24:09 pm by arobwk »


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