2004 JCB 8027z sn 898504 with weak section P3 on nachi hydraulic pump. I began to have a weak right track and decided to investigate as the problem became worse recently. I ran a pressure test via the maintenance valve and only had about 600psi when operating the right track. I inspected the MRV which had no apparent sign of damage. I swapped the MRV from the good track section for the weak section but had no change. I then swapped the P2 and P3 hoses directly from the pump it self and the weak section when to the left track which leads me to believe it's a fault in the pump Itself section P3. The pump is single variable displacement piston type with two (P2,P3)equal outlet flows in tandem with single gear type, driven directly from the engine crankshaft. Does anyone have any input as to why this could be happening/had this happen. Pump is Nachi pvd-1b-24p-11ag-4754g Thanks Jon
Good day From the thorough trouble shooting results suggests that the fault is within the pump unit since both pumps are delivered by the same piston unit it is only the valve plate that splits the flow to provide two outlets. If you feel comfortable split the pump down and inspect the unit. Kind regards Uffex
Oops missed the attachment
Thanks for the reply. I will end up splitting the pump for further inspection. I've attached the parts diagram. Do you think #6 plate could be the culprit?
Good day F M For sure the valve plate cracked or chipped kind of damage would explain the situation, we are thinking along the exactly same lines. I believe the plate is not available as a individual item you may need to buy a repair kit if that is the case I would look at alternative pumps to compare value for money. Good luck Uffex
Illustration may be helpful Kind regards Uffex
This is what I have on the valve plate. Please see attached. Tell me what you think?
Good day FM Its no so easy to see, what does the mating surface look like? I was of the opinion that the valve plate would appear more obvious, specially I suggest the passage of fluid is either to the outer circumference or crossing over from one port to the other from what i can see is there some erosion to the surface (Water in the fluid) check for bearing movement. If all else fails could you find a pump test rig nearby. Kind regards Uffex
Severe wear is kinda sneaky! It will probably not show up on excessive case drain flow because the leak is cross port! As you see there were absolutely no contact between valve plate and barrel end for a while now! Or this pump sat idle for many years. What is your barrel port end looks like? I suspect the brass/bronze plating on barrel is peeled off and gone!?
Never messed with Natchi! But I have doubts that’s a genuine part you showed!
Thank you so much for your replies. Attached are a few more pictures. There was a little pitting on the inside of the valve plate where the shaft goes through. Also around the outside of plate and in between some of the small holes for discharge. There was a very light rub mark on the inside of the valve plate facing the piston barrel. The barrel and pistons looked great. As for it being original I'm not sure. I bought the machine second hand with 865hrs. What are you guys thinking the issue is? Thanks
More pictures
Well! There was a problem with yours first four pictures - you showed wrong side!
I don’t like the concentric grooves on the other side, on bigger diameter! Looks like it’s spun before! Does it sits securely in the notch?! On the “working side” do you see thin concentric grooves between two sides?! Get mechanical pencil, drag it across those grooves. If you feel the tip catching - you need to lap valve plate to the barrel, same thing goes for barrel end! Manufacturers want you to replace grooved component, but you can try lapping them to each other!
Did you check center pivot for a leak?
TVA would it be ok to talk with you over the phone?
I have more questions then patience for typing. Lol
That’s OK, I don’t see anything VERY wrong with that pump per what you showed, still need to see barrel ports and pistons/bores! But question remains: did you check center pivot?!
In not sure what the center pivot is? Or where its located.
Uffex, sir! Do you have more information on this pump? Looks like it takes its suction from the case, and it’s not bent axis pump! Is this correct?!
I'm not 100% sure if the valve plate was seated properly because when I cracked the case it was laying loose on the shaft.
Don’t worry about that! It doesn’t matter now! I sent you PM!
Huge thanks to Uffex and especially TVA (Vlad) He racked his brain and took the time to review my issue. He found a piece of metal partially blocking the pump and restricting flow. He only had a picture. I'll keep you posted on the results when I get it back together.
Thats great help TVA well done I assume further information is not required, hope it works good but where has the metal appeared from ? Kind regards Uffex
That may be partially blocking flow, but you really need to find where that piece of metal came from. Something that size lodged in a block port is only what couldn't get through.
Might be piece of broken off divider between two cavities! That system is goofy! They treat it as separate pump, call it P2 and P3. But in essence it’s the same pump with two separate outlets! The manual for that thing is messed up and confusing, has conflicting information! I was looking at the system and couldn’t understand how one circuit can have lower pressure and would not affect the other one running basically same pump?! And there is no flow dividers or even priority valves! So concluded that is got to be something with the flow! Even suggested hose flapper, but what OP swapped was hard steel lines! That is replacement pump BTW, it’s painted matte red and rest is semi glossy black!