I am having an issue with my 2012 JCB 3cx. Front loader lifts and drops fine, but while digging, the front loader will not hold pressure down. After a few seconds of digging, the front loader will lose down pressure and thus I will lose the stability on the front of the machine and continually have to push the loader control back down, and repeat. I’ve had both cylinders re packed and the issue remains. I’m sure it’s somewhere in the loader valve, I just don’t know where to start.
Try looking for a operators manual and whether or not you have a "smooth ride selector system" ? I'm not sure how this works but I have a hydraulic schematic that shows the lift cylinders are connected to accumulators via the selector valves but the pressure down side of the llift cylinder will go to tank if the selector solenoids are energized, therefore you cannot create and maintain down pressure, also if the selector solenoid is working electrically, then it may be leaking down excessively or have a blown seal. Kind regards
I do not have the smooth ride option on my tractor
Loader lift up down, bucket curl up down are all linkage to spool, manual controls. I do have a clam shell or 4 in 1 bucket, the clamshell is ran electronically from a lever on the handle, all other functions to run the loader are manual controls
Can only assume that the control valve is leaking down the cylinder pressure. A high pressure ball valve installed on the collective return hose from the rod side of the lift cylinders can be used to determine if this is the case otherwise I would think the only cost effective solution would be installing a counter balance valves (over center valves) as the machines valve bank will normally leak down oil on a closed center spool even if it is a new valve bank due to the required spool machining clearances when it is manufactured. JCB did show counter balance valves installed on the lift cylinders on some older 3cx models. This ensures that when a hose bursts the lift arms wont come crashing down to the ground. see attached diagrams.
I did purchase and install HBCV valves on the loader cylinders and they did nothing to help the issue
if you can possibly show some pics of these valves and how they are installed on the lift arms then this would help me in trying to isolate the fault. If the valves have any manufacturing numbers or parts numbers please include this info as well. Best regards
Did you install those valves after having the cylinders rebuilt, to help alleviate this issue. Trying to track the work done here and how long has this issue been going on? Any major changes or work done recently? These are all valid questions, that will help us all troubleshooting. Would also help, if a moderator could merge the 2 threads we have going on this. Thank you.
The part JCB part numbers on the valves are 25/221401. The valves were installed after both lift cylinders were rebuilt. No other changes or work done, I’ve been having the issue for a few months, probably over 6 months. I am the only one who works on the tractor, although I do not re pack the cylinders personally, I do take them to a shop that I have been using for years that does great work honing the barrels, checking for rod straightness, etc on my cylinders.
I’ve attached the diagram in the parts book of exactly how they were installed and plumbed. I did speak with a JCB mechanic and he did tell me that it is an mis conception with these valves function as check valves. He said they would not help with bleeding or drifting so I have already taken them off. They were not helping and slowed the cycle time of lifting and especially lowering the loader significantly.
I may have mis understood the JCB mechanic, it makes no sense to me how these valves could hold cylinder up if a hose was to burst. In any case, the issue I’m having is the cylinder unable to hold pressure down, so it is bleeeing upwards. It does not move up on its own, but will move up when upwards pressure from digging from the hoe side of the machine is applied to the front
The part # for the loader valve is 332/F8149
I don't think the load holding valves you had installed is a dual counterbalance set up meaning it will only load hold on the base side and not the rod side but i will look at the numbers on the valve you had installed and see if this is the case. Thank you for the pics as this helps a lot. Best regards
Thank you so much for your guy’s help, this issue has been very difficult to figure out
Once again thank you for the pics and diagrams. From this I can see that the load holding valve in your diagram pic 0558 has been installed and plumbed incorrectly so this would create some operating issues, secondly these are single counterbalance valve assemblies so as you mentioned they will not lock out the lift arms when the lift arm cylinders are extending out the rods which occurs when the front end loader bucket is forced against the ground by the pivoting action when digging with the back hoe. When set up correctly the load holding valves will lock out the load securely in the event of a hose burst and will loose 1-2 drops of oil per minute at its maximum rated pressure. It is most likely that the cylinders may be bypassing back at the control valve spool if the cylinders have recently been checked and resealed. A High pressure ball valve can be used to lock off the rod side of the lift cylinders but the pressure is then trapped and can amplify until something bursts. you could try plumbing the load lock valves you have to the rod side however it may create annoying delays in raising the lift arms. last option is to install a dual load locking valve. This will most likely affect and possibly delay your raise and lower operation of the lift arms. Hope this information helps Best regards
How does the float detent work? Is it pronounced or is it a mushy feeling on the stick? I am still curious how the spring and seat looks on the check valve on 67c. So, if you raise the front of the machine with the bucket and you put the stabilizer down, does the front of the machine just drop down?