I've got a cat 325l long reach with app 10000 hrs on it serial# 6KK0012K It started out with no power and a hydraulic chatter noise while raising the boom the other functions seamed normal. I checked pump psi both were around 4000 psi so i tested pressures at boom cylinder and it was about the same but while working the machine it lost hydraulic power to all functions. Boom up is only 1800 psi, boom down 900 psi at the cylinders. Checking the pumps pressures they are low all the time. I flipped over ride switch and it didn't make difference. Thanks for the help
Sounds like you lost a piston
Pumps were probably cavitating giving you warning
Pull the suction strainer in the hydraulic tank. I've heard the kind of noise you describe on a machine a leaf licker poured dirt into.
I’m assuming You mean a piston in the pump.
Yes. But check the strainer likeJohn said
Check first filters
Filters have Approximately 20 hours on them
20 hours ago the pressure was ok now its bad so filters can be contaminated
So the filters were changed. Then it started messing up?
The customer changed the hyd oil and filters and have app 20 hours on them. Does anyone have the procedure for checking and adjusting the prv valve?
Is there any chance that customer also drained oil out of pumps and didn’t fill pumps back at the recommissioning?
I wouldn’t think so. But I don’t know for sure
I did find out some prior history of the machine before my customers got it. It’s had numerous different hydraulic problems and it’s had 2 PRV valves put on it in the last 2 years the Pump was supposed to of been rebuilt three years ago
Hey CAT guys, is there a ways to tap in to suction line to mesure vacuum on that machine?
Piston pumps can't "suck" the oil is pushed into the supply side by atmospheric pressure. You made me think of something! I think this model has an air pump that pressurizes the tank to help feed the pump. If it has failed then that would have explained the pump cavitation sounds when you called for max flow. Due to the air pump failure though. It sounds like the main pump ate its self.
I didn’t know about air pump, I always thought that tank pressure was building up by system heating up and by case drains.
On the other thread, chap from Oz. Found what killed his pump - rag in the tank! And gat this - Daikin pump on the CAT excavator! I don’t think we have those here for n US! Only Daikin I know is refrigeration equipment!
I can't find the thread!? Rags can be quite troublesome!
It’s a CAT E140 thread.
R20d12 do you remember if 320b should have that pump, and is it electrical?
Pretty sure the b doesn't. It is electrical and behind hydraulic tank.
Does the gear pilot pump gets its suction from suction pipe or from mains case?
Think its got a pipe but I Dont remember. The presence of the suction pipe should be obvious. Ill check out the thread
The pilot sits inside the main it’s invisible. Most important question- should wa have stand by the pressure on main outlet at engine idling and hydraulics locked?
The problem seems to be in the pilot system because the main pump won't stroke unless one of the spools in the main control valve shifts and causes the negative flow oil signal at the pump to be reduced thus stroking the pump. Your going to have to tee in to the pilot system. I always did it on top of the control valve where its easy to get to and then just use that function to check it. If you have oil there, its getting through the lock valve. It has to be close to what you measure at the pilot pump or you could have a blockage. Were the batteries unhooked when the starter was changed or did a wire get shorted? Because that opens up a whole new realm of possibilities
That’s the answer I was waiting for for two days!!!!! His PRV pressure is 400psi which which in my book is full destrock ( but I’m not a CAT guy )
Looks like we’re highjacted this thread! Sorry rclay1981!
So I got to ask you if I understand correctly: there’s pressure switch on pilot line which when it makes contact sends the signal that armrest is down to ECM, and ECM adjust the PWM signal to PRV valve to lower pressure to “stand by flow”? Kawasakies I’m dealing with have mechanical minimum flow screw, and PRV is for adjusting the flow according to mode or for torque limiting.
I will explain the best i can. If I talk benieth you at times I Dont mean to. I just want everyone to understand. .. There's a mechanical micro switch on the handle. It activates a pilot solenoid under the cab. That system is separate from PRV stuff. It only stops operator from accidently moving controls Engine running. Joysticks in neutral... Return oil (negative flow oil) moves from main hydraulic pump. Through the center of main control valve (because its open center system) Across the negative flow relief valves to the tank and also a line to the pump lets it know all controls are at neutral. Internally the pumps communicate hydraulicly by a "cross sensing circuit" At this point. The pump is at minimum angle. When a joystick is moved. Pilot oil moves the main control spool for that function. As it shifts that spool. The return oil passage begins to be blocked off. Reducing the negative flow signal to the pump. The swash plate spring is able to push the pump to MAXIMUM angle. This causes the engine to bog down because of the load. The machine ECM watches engine rpm via the speed sensor in the flywheel housing. As it gets to a factory preset rpm. The ECM sends a PWM (pulse width modulated) signal to the PRV which in tern sends oil from the pilot system to the pump and destrokes the pump and keeps the engine at the maximum horsepower setting through the digging cycle.
325 has no pump to pressurize hyd tank, only a cap with vent valve. At idle you should have about 2000-2500kpa standby pressure from both pumps. In the suction tube there's atleast 2 small connections which is plugged or has hose connectors, you can use one of them to check if suction is restricted. Take case drain filter off and turn it upside down in a clean bowl and see what comes out, if it looks like an episode of gold rush you are in trouble.
Oh I just re read it, there was a misunderstanding I’m sorry for making you work and typing all of that - but I know all of that! Two things: 1) OP has no stand by pressure on both main pumps - basically no flow or very little flow to control valve. 2) gentleman going by the handle John C, which appears to be knowledgeable CAT technician said that you can’t have stand by pressure because it is open center system ( although a lot of people call it closed center because of those relives ). Since I never worked with CATs and Rexroth ( my experience mostly with Kawasaki), I sit and wonder if it normal to not to have the stand by flow/pressure, so the thought came in maybe there the provision that if armrest is down the PRV destrocks pum almost to zero. Now I know that’s not true! There’s a PTO pump for harvester which don’t do squat now but worked fine perfectly before starter change out. Although all we know about pilot pressure that’s solenoid clicks and hoses shake, and PRV pressure at the pump is 400 psi, not having a stand by pressure(flow) is highly suspicious !
"Gold rush"
So it’s 300-350 psi stand by P.
No piston pump goes to zero angle so... Your negcon reliefs will give it stand by pressure.
I know, but my thinking was maybe the flow so low that drain orifices cannot restrict flow to build up pressure. So all day yesterday I was looking at pictures and diagrams of A8VO and looking at the gear drive, thinking maybe something happened to it and he lost drive three piston pumps and retain only to gear pump but now I know that it is impossible. Now I have another theory about restricted suction, as he has three piston pumps (when ch not known for good suck ability) which produce almost no flow, and one gear pump ( with better suck ability and lower displacement) which seems to be doing OK. And that’s beside not knowing what is pilot pressure at pilot control valves.
So I would say. Zero stand by takes you back to the main pump. This would be such a great one to work on first hand! Plus, I looked totally sexy in my Cat uniform.
Your gonna have to travel to Alaska for that!
The main question is - what the hall all of this got to do with replacing the starter?
If they would take me whale watching we could work something out Lol. Ive actually considered driving up there just cuz it looks so purdy on tv
I still think someone made a quick arc and hoped it didn't mess things up... But I was wrong once before
Maybe little too late than s year, unless you like cold weather!
Just remembered... (There's nearly 30 years of tractor knowledge to shuffle through) I once had a trackhoe that had a plugged screen in the pilot passage in the center of the main control valve. It only let the hydraulics of one pump work. "Suckability" you should write service manuals!
Grew up in cold weather. Can't stand it now! Im a southerner! Even got the accent to prove it!
Which reminds me: I took a brief look at the Kobelco SK 120 on my way back from another job, that POS was doing half ass job, seems to ran too high of a negcon pressure. Maybe it need the orifices cleaned out. Also was hanging at arm cylinder bottomed out.
I was born in Ukraine, lived in Seattle for 20 years, then moved to Mobile - talking about cultural shock!
Arm cylinder hanging sounds like main spool hung due to trash in the system. Maybe arm cylinder coming apart?
Wow! Yeah! You went from snow and beautiful women to rain and ugly hippies to warmth and beautifull women!
I wouldn’t count what goes on in Seattle - rain! It’s more likely he 9 months of non stop drizzle, followiled by 3 months you f scorching heat!
But I loved it there! Just couldn’t afford it anymore!
I've only ever had a spool fail to center caused by trash or broken centering spring.
Trash in that thing is highly possible!
So does Anyone have the procedure for checking the PRV?
Hello rclay1981! Want to apologize for highjacking your thread again. I’m afraid I’m going to get scalded by others but my method is remove and plug the hoses and try to use the machine. If your engine boggs down then your PRV is leaking and pump is good. If not - then the problem with the pump. Provided, of course, that you have good pilot pressure all the way to control valve.
Or you can find 0-10 ampmeter, connect it PRV solenoid in series, at in to PRV signal line with 0-600 or digital gauge, start operating the machine and compare changes of current corresponds with changes of pressure. Or find some kind of current regulating device disconnect solenoid from the machine’s circuit change the current using the device and watch change in pressure.
check pilot pressure on that 325.
I capped all three of the lines it didn’t change anything. Their Was zero pressure at the PRV valve with the lines hooked up or capped off while testing. Pilot pressure is 500 psi at test point and 425 psi on top the control valve. I did notice today that the pilot pump line was getting extremely hot really fast like it has internal leakage. What do you think the chances of the main pressure relief valve going bad all of a sudden is?
I would say something but lately it seems I caught a case of “foot in mouth” disease!!!
We all get that once in awhile