We have a 1992 Hitachi 270 Ex LC excavator. It will run well with the hydraulics working properly but after 10 mins or 20 mins of operation its like the hydraulic power cuts right off to almost neutral very weak the machine will barely move. but if I play with the levers sometimes it takes a minute or more the power returns back to normal until later on maybe 20 or 30 minutes the same thing will happen again. Sometimes closing and opening the hydraulic lock lever along side the seat brings the power back. The machine does run smooth with no shake or stutter. I do notice that when I extend the boom to the end of its reach when it brings up the motors revs slow down like under strain. When working properly the machine has good digging power. If anyone has had experience with this problem or has some advice it would be greatly appreciated. Not sure where to start.
Start by checking servo and main pressure.
What exactly is the servo. Where would it be located. I probably should know this.
What you have on that style of main pump is port plate separation. Sometimes it will lift off with no noise sometimes it lifts of and on rapidly and you get heavy pulsating in the main pressure line off the pump. (sounds like hammering) When the port plate separates the pressure drops right off. Very common on EX270,300,330,370 as they all use the same pump with different regulators.
Servo or pilot pressure is the oil supplied to levers in cab from servo pump which operates spools in main control valve to allow main oil flow out to your hyd cylinders/motors. A servo filter is located beside hydraulic pump. Tee pressure gauge in there to check pressure, should be about 40 to 45 bar.
Would this be a major repair to the pump. I also seen on some other similar posts about hydraulic problems that maybe a pressure relief valve sticking. Could that be a possibility also. Thanks for the reply.
If it was my machine I would pull the pump and change the head and the port plate. This is of course after proving the problem. Not that big of a job. In my experience on 270 machines I have not seen a "sticky" relief valve.
Yeah could be relief valve sticking, thats why I would check pressures first to find that out. Also when machine gets weak, does both tracks get weak or just one?
Yeah just one the right side track gets weak I believe my dad told me that last time he run it. I'll verify that myself later. What could that mean if only one track gets weak when the rest of the machine loses hydraulic power?
If just one track gets weak it narrows prob down to one pump, should be left pump if right track is weak. Could be prob with control signal to pump or pump itself. The way I would check this is, when machine gives trouble, swap signal hoses from left pump to right pump. then track machine, if other track gets weak then its your pump displacement valve sticking, if same track stays weak then it pump trouble. Signal hoses are small hoses on top of each pump. One goes from pump to front of valve chest, the other to back of valve chest. Hope you can understand what I am trying to explain.
Ok sounds like something good to try. Thanks for the replys. I appreciate it.
Sounds like ken al hit the nail right on the head. The port plate(swash plate)is getting stuck in the rear main cover.The cheapest fix is to replace the swash and rear cover on both pumps and it is a job that is best left to a qualified tech.
Sk120 has it backwards.The left track is powered by the rear pump until you dig and propel at the same time.Then one pump works the dig and the other propel.You can isolate whether you have a propel problem or a pump problem by using that method.
I agree it could be head and port plate problem but I also believe in being sure pump is problem before taking it off and bringing it to someone who will recondition it even if its the problem or not. There is 2 pump displacement valves on valve chest, 1 to control each pump. If 1 of these valves stick, which I have seen a few times, it will cause digging functions to slow down and 1 track to become weak. Switching control pipes is a simple and inexpensive test to do.
Thats another way of putting what I said "should be left pump if right track is weak" which would mean that the left track is powered by the right or "rear" pump.
In my experience I have not seen sticky pump displacement valves on an EX270-1. EX270-5 Yes for sure! Same with relief valve have not seen a "sticky" relief valve on EX270 machines either the pressure is good or not. Without experience you could have 2 gauges plumbed into pumps and read a sudden loss of pressure. Now is that pump or relief? I have two gauges with long lines off both pumps and I operate it to know which function/pump is being used. Just was saying in my experience it is usually the head and valve plate wear. So what you need is someone well versed in Hitachi EX270-1 hydraulic troubleshooting on site to nail it down.
did not mean to offend sk120.I always remember it as left has 4 letters (rear) and right has 5(front)The problem with the old dash 1 machines is that no one changed the hydraulic oil until it became the colour of that beer they drink in ireland,As a result the oil suspending the swashplate hydrodynamical would breakdown and the swash and the back off the pump where it rode would get deep grooves in it.When it got warm it would stick and either stall the engine or not pump enough oil to move the machine.You can replace the swash and pump section on the machine but it is a job that requires some skill.And once you have gone that far you should replace the hydraulic oil as well.The old dash 1 was a near bullet proof machine and I don't know why they didn't keep that design.
Did you ever replace the suction filter in the tank, maybe have someone do a case drain check on the main pumps, If you are having a problem with the pumps your case drain would be high propably over 7 to 8 gals per minute. easy pumps to rebuild though have done a lot of them.
Hi I have a EX270 to and had same problems to. Had service check it out and put on a used pump rear one. Problem under slow speed tracks move and bucket cylinder moves good. High rpms left side locks up and bucket cylinder moves slow. Old pump case pressure leaked in gear box and made noise. New pump ( used )quite now lifts good turns good now were it before change did not turn at high rpms. They checked other pump said was ok. Changed regulator on top with old one still does the same. Any idea's ( new oil filters screen in take clear) Year 1994
Sounds like you still have a problem with both pumps. I believe back pump supplies the left drive and the front pump supplies the bucket. The failure that you describe is popular for 270's, 300's and 330's. The back plate in the pump gets worn out and the pump stops flowing oil in high pressure applications. You should have both pumps disassembled and inspected. Before reinstallation of the repaired pumps make sure the bottom of the tank is clean w/ no metal in it.
Deere tech Thank you for your reply. The EX270 repair guy checked pressure on front pump and pilot pressure. The front pump he said was right up there and pilot pressure was all so up to pressure. What it was at first jumping hose under pressure, then got worse, then at high rpm no lift, no turn like all functions stopped. He found right pump did not have pressure and found oil was going into bell housing coming out filler tube. They sell and repair Hitachi. I bought the used pump off of them with them unsure of the used pump. But it was to work and was the only one they found HPV145C pump. Now after pump installed it spins lifts boom at high RPM s but with sprockets in front to drive left side locks up and bucket works very slow. They said the right pump I put on drives the left side and runs bucket. So Now I am confused some what if the used pump is bad to. Its a older machine so I was trying to keep cost down. Tank was clean new oil was put in and filters were just put in. Used oil was darker dirty. Took paint strainer ran last of oil from were filer sets in seemed clean was unsure of 3 small dust size flake was brass or not in sun light. If moving at low RPM s and to high RPM s it don't lock up. Any other thoughts on this? Thanks
I may have confused things a little bit. Operator, service and parts manuals refer right and left track to the side when the track drives are behind you when your sitting in the seat of the machine. One easy way to remember is where the tracks are when your sitting in the seat and the machine is moving forward when the travel levers are in the forward position. Keeping this in mind is the problem with the right track or the left track? The right track is controlled with the same pump that drives the bucket. That should be the front or the left pump, (assuming that you have an older 270 in which the pumps are located behind the cab, not on the opposite side of the cab or the right side of the machine as your sitting in the cab).
Thank You for helping me. I seeing if they have another used pump. I think it might be bad also even it was up to pressure. Thanks again