New here. Working on my old LIEBHERR 945. Hydraulic tank is up to the proper level. No obvious leaks. I can post some photos if that helps. Thoughts? Thank you in advance
Good day Sounds like low servo pressure, if you have a hydraulic schematic may be able to help some. Kind regards Uffex
^Was thinking that if it is pilot contolled then the pilot pressure was the problem ^ They make a new R945 to confuse the searching, but I found this video posted by @skadill a year ago that looks like the right thing. It appears to have pilot controls.
Update Received my new hydro pressure gauges today. My basic plan at this point is to test the pressure from the pump at low rpm and then at high rpm. Hopefully see some proof of whats not doing what it is supposed to do.
Anyone have advise for us when hooking up the pressure testing gauges? Here is a photo of what I'm looking to tap into. Does anyone see a pressure relief valve in this photo? It would be great to test specific functions and pressures without having to drain the reservoir tank in order to remove the pump for visual inspection of the internals.
Please tell us where or what the spool block is. We don't have a lot of experience with this.
Follow the hoses from the hyd cylinders, they go to the spoolblocks. Perhaps you should employ an experienced mechanic before messing about with high pressure hydraulics. I understand you have no experience but if you have zero knowledge then hooking up pressure gauges without knowing what you are looking at will be pointless in my opinion
What I meant was I haven't had much experience working on this excavator. The knowledge base in my shop covers everything from race cars to heavy ag equipment. This Leiberr is an old girl and I can't find a service manual anywhere. Can we confirm that what we are looking for is not in this photo?
Maybe the part you are talking about is in one of these photos?
This square part looks more likely to be what we are looking for?
Yes, the second photo 135426 shows the spook blocks, Main relief valve is on the right of the four spoolcaps, hex locknut with Allen head adjuster in centre
This looks to me like a pressure testing manifold. Am I right?
I removed and disassembled the PRV. Not seeing any damage. See photos Photo #143642 shows wear but nothing major
correct
Progress. I got my new pressure gauges attached to the testing manifold. At wot the gauges show ample pressure. Everything operates.... a little jerky but not bad. When I back off the throttle 20% the gauges show nothing, everything stops working. After researching the Linde AG main hydraulic pump B2PV105 it looks like a rebuild kit is available for about $1,500 usd from China. Has anyone on this forum ever rebuilt this type of pump? I have searched everywhere for manuals but can't find anything. If we have to pull the entire unit from the excavator we have the machinery to do it. However, it would be amazing to find out if the unit can be rebuilt / repaired by opening up the case when it's still in the excavator. I realize this might be a long shot but worth looking into. I will attach a few photos with some red labeling. Not fishing for free spoon-fed advise. We are happy to pay for direction with this situation. It would be frustrating to pull the entire pump and find out the repairs could have been made while it was still in the excavator. I am currently rigging up a larger pressure test system that will be right at the pump pressure outlet. Probably worth the effort to make sure the main pump internals are the problem.
The kit in your photograph is only the main barrel and pistons, this is not a rebuild kit,,you will require two of these,plus servo shafts,bearings,seals etc. The pump will need to be removed for overhaul/rebuild. Linde made good pumps and I suggest you contact them or one of their distributors. A good hydraulic shop should be able to overhaul this pump but I would be very wary of using Chinese components from a quality standpoint.
Thank you for your advice. I appreciate it. JH
Update Local Hydraulics tech had the following input. If the pressures meet specs at full throttle there probably isn't anything wrong with the pump(s). He explained how there was a hydraulic system on top of a hydraulic system in this Lieberr. He explained in more detail. We are trying to find the valve, or vane that adjusts pressure depending on throttle position. Does this sound familiar to anyone?
This 945 has HYDRA FORCE. See attached photo
The hyd pressure is set by the main relief valves not by engine speed, the hydraulic pump output flow will reduce as revs drops but if the pump is good pressure should be maintained until near stalling point. A worn pump will usually not maintain pressure as the rpm drops
Understood. The diagnostic detail I noticed is how the pressure "behaves" Full throttle = Full pressure on test gauges Slightly drop rpm's by 20% = All gauges go from full pressure to 0 pressure immediately. All lower throttle positions = 0 pressure / nothing works Would a worn pump build pressure as the throttle goes down proportionally? Seems like a red flag that the pressures go from great to zero immediately below 80% throttle. I have attached a few photos of the main assembly with the tank cover off. After removing the cover we ran a magnet through the bottom of the case looking for any evidence of broken parts. Nothing. Completely clean
How are you measuring pressure, you need to end stop a cylinder and hold it end stopped to see what pressure the main relief valve opens at, as you slowly reduce the engine revs the pressure should be pretty constant ,if the pressure drops at the same time as the revs this is usually an indication that the pump is worn. Have you checked the main relief valves ?
PRV inspection a few weeks ago. Everything looks good. No obvious damage.
I agree. Pressure should drop proportionately with engine rpm. It doesn't. It drops suddenly from good pressure to no pressure
I meant to say the pressure should not drop proportionately with engine rpm. typo
Update. I decided to dive in. After taking the pump apart I found a few issues. 1. Bad O-rings 2. One of the pump cylinders turns too easy.....feels loose / wore out? See photos
The pistons look to be scored,, maybe it's just the photograph,what are the barrels like inside,can you see or feel any scores of marks?
Everything feels smooth. No scores. Got new O-rings One pump hub was a bit loose. Tightened to specs. I'm getting ready to put it all back together.
On the bottom of the piston barrels there should be a brass running surface, ensure there are no scores on them as this runs against the swash plate and any marks or scores will cause a drop in pressure
I checked the brass surfaces. Nearly perfect condition. Almost no signs of wear. However one of the pump barrels will spin by hand much easier than the other. Can I assume the loose spinning barrel is a sign of wear? It appears to be adjustable.
Sorry I don't know about that but best of luck anyway, keep us posted after you rebuild the pump.
Both pumps are within specs. Pressure is within specs. Could really use a flow chart. That would clear up a lot of questions. Can we buy one from someone? anyone? JH PS. What are the two air valves for in the cab? Something important? See photos
I think the air valves are for swing and travel brakes
We are looking everywhere for an operators manual. Anyone have one for sale? 1973 Liebherr 945
Update Found a tech manual with flow charts! With some luck it might point us in the right direction
Problem solved. Pumps are fine but the housing was built to pivot. The pivot seals were bad. Basically it was pumping most of the pressure back into the pump sump. $20 in parts to repair. Labor was a bit more than that.....JH