It seems that one of the pump stages has a problem putting out only 45 bar. This affects the dozer, slew, swing and dipper boost. interestingly the slew will work slowly on higher rpm and accelerate when I engage the boom-up service just enough that the boom is not really moving fast. This confuses me as I don't see any connection between the two. The slew is also drifting when when the machine is not completely level. Additionally none of my 3 M.R.V. are adjustable. No matter what direction I turn the adjustment screw the pressure never changes. I have put a new M.R.V in the slew, swing, dozer, boom boost section, but there is nothing to adjust if only 45 bar are getting there. On services where the M.R.V. is supposed to vent pressure at 240 bar, no venting takes place and the pressure rises to 320 bar when at the end of the stroke. I believe that this is probably the maximum that the pump can deliver. These pressures are hard on everything on the machine. I am attaching the hydraulic schematic, but apparently my valves are not in sequence of the schematics on the valve block. Since I bought the machine used, there is no telling what happened before. However, when I received the machine it was working perfectly and performance has deteriorated over the last 500 hours. I now have 2000 hrs. on it. Any information, any advise would be appreciated. Thanks Karl
Can you supply a serial number please. Drifting of the slew can be the cross line releif valves in the top of the slew motor not sealing correctly or stuck open with dirt/debris. Perhaps you need to do a flow test on pump so you know are starting with a good pump/bad pump. PMV or the pressure maintenance valve blocks are a common fault on these smaller machines i have changed quite a few, these normally wont allow any thing to work servo circuit until you pressure the block via the blade circuit not servo operation to back feed as to speak as all 3 pumps supply this PMV. If item no 16 check valve is not seating you may back feed the pump . These also suffer from dipper rams breaking up and debris going back to valve block the dipper boost section has quite a few ball and shuttle in there so any crap can cause issues. Pull hyd filter and check. Need the serial number to look on my info .
Hi Jeff and thank you. The serial # SLP08032E08999777 I have replaced one of the cross line relief valves with a brand new one, cost GBP 480.00 ($ 615.00). I have 2 of those and the drawings show 2 on one of them and only one on the other. JCB confirmed that my machine only had one, but there are really two. Anyway, I assumed that if I replace one of them I should at least see a difference in one of the two directions, but nothing changed. Therefore I guess that neither the original old valve nor the second original valve are faulty. As far as the new PMV is concerned, I made an error in my original post. I meant to say MRV`s and not PMV. The PMV seems to be working fine and we also installed a new cartridge and adjusted the servo pressure to 26 bar (actually 25.5) according to the manual. Item no 16 check valves I have also considered, but I have no idea where they are located. Presumably in line with hoses, but it is a nightmare to follow these in a small machine like this one. I have used the machine almost daily and the slew problem gradually got worse. The Dozer Seals started to fail to the point that the blade sank to the ground within 5 seconds. It was a pain in the neck to move the machine and remembering to lift the blade first. The bucket cylinder was drifting slowly as well until it would reach its neutral center of gravity. Finally the bucket seals failed completely and oil was gushing out through the wiper ring. Now we replaced the bucket seals, the dozer seals, the swing seals. We completely removed the hydraulic tank cleaned it, installed new suction and return filters and filled it with new oil. We did a lot of other work as well, but this is not related to the hydraulics. We spent over $ 6,000.00 on parts (including extra parts for spares). The first thing we tried after we completed the work was the slew. It was rotating equally in both directions, but with the machine not completely level it slowed down on the "uphill side". Instead of 8.5 revolutions per minute we clocked five at full throttle. We had the pressure gauge connected (purchased a test kit as well), to the test point on the PMV and got a reading of 100 bar. The second thing we tried was the dozer. We again got a reading of 100 bar, obviously not enough to lift the front end off the ground. It raised partially and then stopped. Then it was moving up inch by inch as I was actuating and releasing the dozer lever. At this point we decided to do the pressure test on the slew. Locking the slew pin and engage the slew motor at full throttle. According to the specs we should have had a reading of 185 bar, but suddenly we only got 45 bar and no more. The same thing on the dozer. Then we replaced one of the cross line relief valves and it still was the same in both directions. Then we replaced the MRV for that particular circuit and nothing changed. We also tried adjusting the new MRV, but there will be no changes visible if only 45 bar are getting there. As a matter of fact, there are 3 MRVS on the valve block and none of them accomplish a pressure drop in their respective circuits when trying to adjust them. I also purchased a test block, gauge and hand pump to adjust the ARVS, but the shipment arrived without the pump, so I have no idea if there is a problem with those. The third thing we tried was adjusting the dipper boost dump valve according to the instructions. Engine half speed, with the dipper partially out, gradually and progressively retracting the dipper ram, the pressure should drop to zero, blah, blah you know all that of course. In the specs it says the valve should dump at 150 bar, but we never go over 90 bar during the motion and because of that it does not dump until the ram reaches the end of the stroke, where the pressure suddenly jumps to 320 bar. So we have really no idea at what pressure the dump valve is set. When looking at the pump drawing it shows an internal coupling on the drive shaft going to what I assume is the gear pump section of the pump. Do you know if this coupling has something like a rubber damper built in, causing slippage because of wear and preventing the gear pump from producing adequate pressure? Just a shot in the dark, but I would like to avoid dismantling the pump unless I have a good reason for it. Sorry for this lengthy message, but I want to give you as much info as possible so you can limit your reply to unanswered questions you might have. Thank you Karl
There will be a steel splined drive coupling between the piston pump and gear pump drive end but this will often just fail and that would be it but its only a case of dropping the 4 bolts off the end and pulling that section. Looking at the drawing of the hyds the item no 16 is drawn outside of the main valve block but cant find on any drawings could be in the adapters valve block end or pump end but op for valve block fittings and i understand they are a pain to find though.it would appear that it is all connected with pump 1 which is the small pump on the back need to do a flow test on it to determine its serviceability as its got worse over time.Did you change the MRV on the P1 circuit?
Hi and thanks again. It appears that I would have to remove the fuel tank to get to the pump. No big deal as this is only 2 bolts. Am I correct that this part of the pump is the gear pump and not the piston pump? I was afraid that there was no easy way to find the check valves. I am starting to believe that my problems are related to a problem that I had last year when my dipper ram piston disintegrated due to a sloppy seal replacement job. You gave me some pointers then as well. I had posted a picture of the metal parts we pulled out of the return filter. By looking at the suction filter it seems impossible that debris would get all the way to the pump and debris in one of the check valves seems more likely. I will try to find the check valves and if there is no problem I will take the P1 off. No, I have not changed the MRV from P1 to another location. I have to get in the boat to go to where the excavator is located and I was waiting for more advice or information on my problem, browsing the web over he last 20 hours. However, so far the best advice or info I was able to find is from you. I will go tomorrow morning and tackle this once again. Thank you Karl P.S. My parts supplier sent me a message also, after he contacted his source at JCB. I am pasting it here: This is just a steel to steel coupling this will not be the problem…………………… I’d say pump is worn out Coupling @ £ 133.65 Collar - No Longer Available Pump @ £ 3748.50
These machines are a nightmare when the ram breaks up common on the dipper they normally contaminate the whole system and can damage the spool block /spool and you normally get ram drift or dropping. The whole system needs cleaning out we used to put these machines through a external filer system to clean the contaminates before returning to tank as bits hide every where. On the valve slices you have a load hold check valve which often harbors debris and also the o rings go as well. You will need to remove the valve block really and strip it down and each valve to be on the safe side im afraid.
Hi Jeff, it is 05:15 and I wish I would not have started my PC this early. I am working in the jungle and basically have no access to anything. Just to get a hydraulic fitting is a round trip of 1.5 days and spending a night in a hotel. I know that you are right, but what you are telling me to do is the one thing I was not prepared to do. Guess I have to bite the bullet. Speaking of o-rings. I have a hard time believing that the o-rings on the MRVS and the ARVS are not available and I have to purchase the whole valve. This is what I was told. They cost like $ 200.00 each. When you look at the drawing they are only listed as a "kit". For example drawing # 3 on the attached drawing. One of the o-rings is to seal between the valve and the ARV and the other one sits on the ARV itself. What is the ARV doing or not doing if the o-ring on the ARV is damaged? My assumption would be that the ARV lets the oil bypass at all times without ever reaching the adjusted pressure. Is that correct? And again, if this o-ring is damaged why would I have to purchase the whole valve? There is no part no. for these o-rings nor for the copper ring that goes on the valve cap, which is supposed to be replaced after removing the cap a second time. Thank you Karl
Hi Jeff, don't know if you can open the PDF from my previous post. I am attaching jpgs now
If the o rings are damaged this can be a source for your loss of oil pressure but the chance that all services are down would indicate the MRV at fault or the hyd pump and not the ARV. The arv are there to protect each individual circuit both ways mostly but some only one way from external pressure build up caused say by when unloading machine and having dipper on the ground and tracking forward thus the dipper will try and tuck under machine, this saves the ram rod from bending and hose and seals from blowing.The MRV will be a possible to look see at and see if any debris have stuck the valve inside open on the seat or to check if the seat has been damaged at all. You can strip them but just take note on how they were assembled.If the o rings are blown they will only be a normal o ring but normally you have a nylon back up ring as well which will support the o ring from blowing out. If the o rings are blown on any you can measure up and may be send to hydraulic company for o rings in stead of complete valves.
Hi I have just checked with my friend in the parts department ant they do a seal kit for the complete valve block but this is only between each slice we think ,no other kit on offer . If you can find the valve block make and serial number may be able to go to manufacturer to get seal instead.
I have checked with the manufacturer of the valves in Italy and was told that they can not sell to me because this block is a "JCB" block. Kind of a vicious circle, like JCB protecting their distributors.
Thought that might be the case so that only leaves stripping the valves and sourcing o rings in the aftermarket world.You need to also check that pump as well would be nice to put a flow meter on it.
Did you ever find the issue to this? I'm having a similar situation.