Okay so I have had both drive pumps rebuilt after having an issue with losing charge pressure cat looked at it and said my charge pump is fine but both drive pumps needed rebuilt so I had that done. When I picked the machine up from cat it was tracking left just thought it was from my pump. I now have the pumps on the machine but what I can’t figure out is now it wants to track to the left forwards but perfect straight going backwards also still having a loss of charge pressure the said drive motors were good
@Cmark
If the Cat dealer did the pumps (after saying they were the problem) it seems they should have calibrated everything and checked to make sure it goes in a straight direction before they told you to pick it up. I'd take it back to them to fix the tracking.
Definitely agree with this 100%, i paid CAT to set my pump pressures, it took a long time and cost a lot of money but setting the pump pressures and going through the electronics under the right arm rest and setting it up that way as well. I still track left a tiny bit while tracking a far distance, but you wouldn't notice unless tracking little bits while working.
My charge pressure is jumping all over the place going down below spec by 30psi at times would I be wrong to think I still have leaking internally somewhere
Need to post up a full serial number for Cmark and Nige.
Did the dealer not do anything other than putting the motors in? They should be making sure everything is working right. The motors can't have been cheap and they're the ones who said that was the problem.
What was the problem in the first place to arrive at a diagnosis of low charge pressure? Is the charge pressure fluctuating when the machine is stationary, moving or both? Was it tracking straight before it went into the dealer? Because it goes OK in reverse, it may just need the engine-on calibrations doing but as mentioned above, that should have been done after the pumps were installed.
So to start with the first issue we was having a lose of charge pressure causing the machine to stall. Replaced the track system sensor that did no good sent it to cat just to have the machine diagnosed they checked motors and pumps said pumps need replaced I picked it up from cat. Took the machine apart sent the pumps off for a rebuild that guy said piston block was bad he replaced both of them I reinstalled them. When I got it back I had someone come out to do the calibration but the tracking was way to far out of adjustment just for a calibration so he tested for charge pressure and it was still low this is all test being done with the parking break locked out so it is under a load. The tracking issue as far as it tracking off to the left has been fixed cleaned out that tracking sensor on the block on the left side of the machine and that fixed that but we still have a lose of charge pressure when it’s locked out ill post a picture of the test sheet with this so you can see the pressure at the rpm’s it pulls the machine down to the machine never goes below spec on the rpm’s this test is also done with each pump isolated.
Sorry I was confusing motors with pumps but still the dealer should have calibrated everything after installing the pumps.
Does it have good charge pressure in neutral?
And we still need a full serial number. There are no less than eight serial number breaks within 2ZN.
At neutral it has good pressure it’s once you start to put it in to a drive direction that it starts to drop pressures 2zn00837
So when you do the stall test, you have the signal lines to the motor servo valves disconnected and capped, correct? That leaves possible leakage paths in the the pump servo valves, the steering solenoid valves, the make up valves or the implement pilot controls. We can eliminate the implement pilot controls because you have good pressure in neutral. The flow requirements of the steering solenoids and servo valves are minimal and I find it hard to imagine a scenario where they develop enough internal leakage to take all the flow away from the charge pump. That leaves the make up valves. If you're confident that the pumps were properly bench tested following the repairs, that only really leaved the motors as suspect. I would say you have high internal leakage in a drive loop and the make up valves are dumping the charge pump flow into it to try to keep up. You need to test the motors case drain pressure. There should be pressure test quick disconnect fittings already there. You will need a low pressure gauge. Anything above about 3 psi means high internal leakage in the motor. Attached power train schematic if you don't already have one. It's for a later serial number than yours but the earlier schematic is unreadable. It will be OK for our purposes.
we capped off each individual servo line. we will check the case drain pressure and see where we r at. i kinda thought if it was a motor it would lose pressure no matter the direction of travel, would i be wrong for thinking that?
When I say we did each individual line I mean like one at a time
I can see the logic in that thinking. That 265 psi Left Forward pressure is still pretty low though even though it's just in spec. I'll be doing some tests on a 963C later this week. It has a similar but not identical system to yours. I'll see what the charge pressure drops to under load. Stupid question, but have you changed the pilot and case drain filters?
I bought all new filters for everything when this problem started I hadn’t replaced them after replacing pumps bc they have less then 5 hr on the filters and that’s just from trying to diagnose the machine
If you still have the old filters, it would be interesting to see a filter chop. When you say you have good charge pressure in neutral, what is it?
420 at neutral I cut the filters when I replaced them didn’t find anything in them
420 psi is on the money. If it's dropping to 200 psi under load then you have a massive internal leak somewhere. Definitely need to check case drain pressures.