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Crawlers, Dozers, Loaders & Backhoes Discussion Forum

Any Hitachi experts?

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Sean in Ireland

08-14-2005 15:34:22




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I have a 6 ton Hitachi tracked excavator(model UHO25)that has a problem. The dipper and bucket crowd services are very slow. There is two speed tracking on this machine but it does not work either. Depressing the pedal for high speed tracking has no effect whatsoever and it is not tracking in high speed mode. It appears that the oil flow from the third pump is doing nothing and simply goes back through the return to the tank. I have dismantled the small valve block that the third pump supplies but can find nothing obvious wrong. Presumably it is supposed to divert the oil to the other valve blocks as required. I have searched e-bay for a repair manual but no luck. If anyone has any experience of these machines I would be grateful for any help.

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ajk

08-15-2005 01:24:32




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 Re: Any Hitachi experts? in reply to Sean in Ireland, 08-14-2005 15:34:22  
As far as I can remember the early Hitachi"s had a fixed displacement gear type multi flow pump,ie layout been one section bolted to the other driven by a common shaft,your problem sounds to me like there is a valve held open or that the end section of the pump is not pumping,I am rusty now on that type system as it is fairly dated,you should have a word with McSharry Bros in Roscommon,you probably know of them.If you have no joy there try HM Plant in Somerset UK.
AJ

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Sean in Ireland

08-15-2005 15:14:18




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 Re: Any Hitachi experts? in reply to ajk, 08-15-2005 01:24:32  
Thanks for the reply ajk. Your description of the pumps is spot on. The outside pump section is definitely working. I switched the output from it to one of the other valve blocks and it made no difference.Havent tried McSharrys but had a mechanic from local dealers (TBF Thompson)look at it.He was no help- said they only took on dealership when EX series were the models being sold and they had no experience of the older models.

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Roy Suomi

08-14-2005 20:00:12




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 Re: Any Hitachi experts? in reply to Sean in Ireland, 08-14-2005 15:34:22  
3rd pump?? Are you referring to the pilot pressure pump. Most all excavators use only 2 pumps to power hydraulics. One for each track then combined flow for digging functions..I'm not familiar with your Hitachi system. sorry. I'll check one of my books and get back to you maybe tomorrow..



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