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Crawlers, Dozers, Loaders & Backhoes Discussion Forum

Excavator Hitachi EX60

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Wilfried

11-12-2005 20:35:47




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After I work the machine for about 1 hour the hydraulic pump seems to run on so high power all the time that it pulls the engine down. If you try to walk the machine or lift the boom with an empty bucket the engine almost stalls. If you release the levers the engine recovers within secondsand idels without an problem. Any idea?
Thanks Wilfried




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123abc

01-17-2006 21:02:49




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 Re: Excavator Hitachi EX60 in reply to Wilfried, 11-12-2005 20:35:47  
The pump angle sensor (a-sensor) heats up and goes to an open circuit. Let it cool down and all is o.k. Sometimes the 1 amp PVC fuse will blow if it shorts when hot. Changing it and adjusting it is another story. Let me know if you got it going.



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Heat Houser

11-14-2005 17:23:55




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 Re: Excavator Hitachi EX60 in reply to Wilfried, 11-12-2005 20:35:47  
It would be helpful if you posted the complete serial number. The prefix indicates the model. For example, 10B - EX60-1T, 10K - EX60-2, 10S - EX60-3, 1C1 - EX60-5(LC) (plus about 15 more EX60 models) To look at the correct manuals, you need to know which model you have...EX60-2, -3, -5 etc.



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bob from ontario

11-13-2005 16:48:48




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 Re: Excavator Hitachi EX60 in reply to Wilfried, 11-12-2005 20:35:47  
some excavators have hydrulic brakes on the track motors are you sure they are releasing



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Randy in OH

11-13-2005 07:00:17




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 Re: Excavator Hitachi EX60 in reply to Wilfried, 11-12-2005 20:35:47  
I don't know the first thing about excavators, but I wonder if, after heating up, a pressure compensating valve spool is not shifting properly. I don't know if these are variable volume pumps, and therefore have a pressure compensating ring or plate in the pump or if they have a pressure compensating valve that dumps excess oil and maintains system pressure from a fixed displacement pump. I've spec'd and installed several industrial fluid power systems, and this sounds like the most logical scenario. It could also be a piece of dirt in the system causing the same issue, but I would suspect that the problem would remain, and not be heat related. If the hydrualic system is normally open, meaning that oil flows freely from pressure to tank when control valves are not actuated, you could be seeing the result of the pressure compensating system at full pressure when you actuate a valve.

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Jonathan in MA

11-13-2005 04:03:14




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 Re: Excavator Hitachi EX60 in reply to Wilfried, 11-12-2005 20:35:47  
LIke the other guy said...check the fuel filter(s) ...also Hitachi"s tend to have a small screen mounted in one of those "banjo" fittings in the fuel lines. Its usually on the top of the filter housing. It fits into the fitting itself...They are quite often overlooked and result in the performance like you are experiencing.. If its not fuel related, then I believe the hydraulic pump is controlled by 2 displacement control solenoids. If one is bad it will act like you are saying...but usually it will be all the time....not after running for awhile... Check the fuel system completely first...thats the cheaper and more common problem..

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ajk

11-13-2005 03:20:10




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 EX60 in reply to Wilfried, 11-12-2005 20:35:47  
It sounds as if you have a fuel problem,replace the fuel filters not overlooking the water trap under the fuel tank if you have one,small plate on the side under the tank,make sure that the fuel is flowing from the tank and the tank it is vented,if your machine has an electric lift pump check to see that it is working,you will hear it going with the key switched on,also look at the air filter,you did not say what engine you have.
AJ

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Wilfried

11-13-2005 06:12:12




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 Re: EX60 in reply to ajk, 11-13-2005 03:20:10  
It's for sure a hydraulic problem. You can hear the hydraulic pump running on high power. There is so much pressure in the hydraulic system that the gear oil of the swing motor is coming out of the dip stick



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Jonathan in MA

11-14-2005 14:41:51




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 Re: EX60 in reply to Wilfried, 11-13-2005 06:12:12  
I don't think the oil leakage is related. If the swing motor seal leaks, it will ppressurize the swing drive gearbox. usually it has its own reservoir of gear oil. If the motor leaks into it it will come out the dipstick tube. Just to be sure we're talking about the right configuration, there should be 2 solenoids mounted to the pump. One tells the pump to pump oil and the other tells it to shut off. they constantly cycle on and off to adjust pump flow for the demand required. If one is bad it will exhibit what you are saying ...Also there are other electrical items that come into play... There is a pump angle sensor that tells the "computer" where the pump swash plate is. Also there is an engine speed sensor that tells the computer the rpm's. This results in those solenoids either swashing or deswashing the pump for more or less output. Whats happening now is that the pump is putting out the maximum oil and thats whats killing the engine. The hard part is finding out whats causing the problem. And thats difficult to diagnose in person...never mind over the internet !!.. Have you totally ruled out a fuel problem ??

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Bob/Ont

11-15-2005 08:49:38




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 Re: EX60 in reply to Jonathan in MA, 11-14-2005 14:41:51  
Jonathan, do you think the hyd oil might be getting a bit contaminated and the Destroking Solinoid valve sticking inside when it gets warm? Are the solinoids both the same inside so he could swap the valves and see if it worked only slow when hot? The plugs are likely different so they don't get wired up backwards but the coils could likely be kept in their original place.
Just a thought.
Later Bob

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Jonathan in MA

11-15-2005 14:22:25




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 Re: EX60 in reply to Bob/Ont, 11-15-2005 08:49:38  
they are the same exact part. They can be connected incorrectly with no trouble as the connections are identical. The harness is numbered as well as the pump housing . "1" and "2"... they are expensive too ...vicinity of 4-500 a piece...



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Bob/Ont

11-15-2005 15:40:44




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 Re: EX60 in reply to Jonathan in MA, 11-15-2005 14:22:25  
I think swaping them would be his best way to go Jonathan. If it works the savings would pay for the solinoid. My car is having the same problem with a converter lock up solinoid. I was worried I spun a clutch, dealer said an oil change and a parts kit should fix it up. Those solinoid valves don't like dirty oil.
Later Bob



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Bob/Ont

11-13-2005 18:35:03




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 Re: EX60 in reply to Wilfried, 11-13-2005 06:12:12  
Wilfried, it sounds to me like the control of the Hyd Pump Volume. Up above the solinoids where mentioned. I don't know your system but what they do is send the pumps a signal pressure that limits their out put under heavy load. They get oil from some place??? if it's the pilot pump maybe it's worn and not delivering enough when it warms up. The best thing to do is to try to borrow a good manual from the dealer and read how the system works. You need to have a good understanding of the system before you tackel it. They are complicated but complicated things are just a bunch of simple things put together. It takes a good meter to measure the voltage to the solinoids too. They use square wave/duty cycle.
Later Bob

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ajk

11-15-2005 15:53:30




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 Re: EX60 in reply to Bob/Ont, 11-13-2005 18:35:03  
The earlist EX60 had a 3 bank fixed displacement gear pump followed by a twin variable displacement axial piston pumps with gear pilot pump,latest is a treble flow with a gear pilot pump,the solenoids are not fitted to the pump but are mounted remotely near the pilot circuit filter by the counter weight,if you have a variable flow pump and wants to know if the solenoids are operating sit someone else in the seat and hold the thin pipes coming off the pump to the solenoids,you can feel the oil pulse if the solenoids open when a load comes on the equipment,in the case of this machine working ok till it gets hot points to the pilot pump been worn and not having enough pressure when hot,the oil coming from the swing gearbox I would say is an unrelated problem and I have changed many a seal on the motor output shaft,the machine has a leak return that come from the track motors through the rotary coupling via the swing motor to the tank,as it goes into the tank it has to pass through the filter,keep the filter changed,the tank also has a pressure valve in the cap and a filter that should not be blocked or too much pressure will build up and restrict the flow of low pressure oil returning to the tank,my advice to you is have someone look at your machine that can test the pressure of the main and pilot system.what model,how old is it.
AJ

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