Hitachi EX27u Low Pressure ?

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le.maisonniau
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Hitachi EX27u Low Pressure ?

Post #1 by le.maisonniau » Sat Jan 13, 2018 1:16 pm

Hi Guys,
I am in the middle of 'fiddling' with a mini digger I bought last summer, bought it 2nd hand in France, I knew at the time there would be lots of maintennance to bring it up to spec - and wasn't wrong.
So Far I have cleaned it all down so it is OK to work on, then drained all the emulsion that was passing for Hydraulic oil out of the tank, changed all the hydro filters, cleaned the suction filter and replaced it, replaced 4 pipes with new (2 x pecker and 2 x Boom)- serviced the track tensioners and idler wheels and got the tracks back on myself (quite easy :thumbup: surprisingly) and have been running the engine/pump slowly over the past week and exercising the rams - ran it up and down inside my woodyard (too wet outside) and the tracks seem really good now - lost the horrid squeak that was present when I bought it - even managed to get the m/c into "high speed" and seems good.

So, my current issue: To me it seems to be a pressure related problem that has me scratching my rear: :( The following tests are done with m/c at half revs.
The dozer blade will no longer lift the m/c of the ground :roll: OR the Boom will not lift the m/c off the ground; depending on whether the dozer blade is up or down :roll:
IF - the dozer blade is down, the m/c is unable push out the boom ram, if I lift the blade up -then- I get full action (pressure !! ) to lift the m/c up,
IF - the boom and dipper are all retracted in, this makes NO difference to dozer.
The dozer blade will, slowly lift up the m/c at half revs, if I push the lever, release push again etc. i.e. sort of teasing it up.

A mate of mine suggests replacing the seals inside the dozer ram !!! he is a supposed hydraulic expert :lol: and has in the past suggested putting washers behind the control leavers on my cherry picker to "boost" the pressure - So not a lot of confidence in his suggestion. He does however have hydro pressure testing meters and Tee's and is willing to help me test the system pressure.

Questions
1 Should I just keep on exercising the rams and expect any air in the system to eventually come out ?
2 Should I go around all the pipe ends and bleed them or check for Oil - Air ?
3 Are there any exercising tests I can do that may point at dodgy pump or controller or something?

Sorry to be a bit long winded (as per) but thought it best to layout what i've done first. :bow:
Hope some of you are still awake :lol:

Best wishes to all for 2018 :thumbup:


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Re: Hitachi EX27u Low Pressure ?

Post #2 by le.maisonniau » Mon Jan 15, 2018 10:25 pm

Update:
Hi Guys, since first posting, I seem to have 'fixed' the dozer blade issue :thumbup: after lots of testing etc, I noticed I was having to put a lot of pressure on the lever to push it down, so I stripped off the covering panel and found the lever was fouling its housing, there was plenty of adjustment, so I adjusted it (shortened it) and 'voila' it works a treat now, up and down no probs, lifts the m/c up and down effortlessly.

However, I still have the problem with the Boom :wtf: , i.e. If the dozer blade is down, there is little or no pressure to lift the m/c by pushing the boom ram down, BUT, in this postion if I turn the bucket - the bucket ram will lift up the m/c :dizzy: - I did replace the boom ram supply hoses :roll: and did check for oil - but will revisit the pipes and check again -

If anyone has/had a similar issue, I would be interested in testing procedures and solution :bow:

The problem as I see it now; with the Dozer blade down, there is no pressure to lift the m/c by pushing down with the boom.
As soon as I get chance I intend to take the m/c outside and see what happens if I try to lift a full 5' scoop up with the blade down, I guess I should get a similar lack of pressure :think: ?


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Re: Hitachi EX27u Low Pressure ?

Post #3 by Jeremy Rowland » Tue Jan 16, 2018 8:27 am

John it's good to hear that you are making progress :thumbup: sometimes issues turn out to have an easy fix at other times they don't; I only have a base knowledge of hydraulics so sadly I cannot be of much help to you with the boom issue, all I would suggest is if there is anybody you know that could check all of the hydraulic pressures for you it may point you in the right direction.

Jeremy

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Re: Hitachi EX27u Low Pressure ?

Post #4 by FOWLER MAN » Tue Jan 16, 2018 3:14 pm

Hi John,
I'm afraid I don't know the Hitachi EX27 but I do know hydraulics. Jeremy is right to suggest that a pressure check is the way to go.

If everything else but the boom are working OK that eliminates a pump problem. If the boom is lacking power both up and down that points to ram seals but if that was the problem you would probably expect the boom to creep.
If the boom lacks power in one direction only that points to a service line relief valve ,(SLRV), fault. ( I think Hitachi call them Overload Valves ). You would need a pressure gauge to check or set up the valves.

As the main line relief valve is set to a lower pressure than the SLRV it is usually necessary to increase the pressure there above the SLRV
pressure in order to set the SLRV and then reduce it to its normal setting afterwards.

As you have found with your blade it's always worth checking that control linkages move the spools to the end of their travel. On a servo controlled machine that can be down to low servo pressure.
I know this is all a bit vague, hope it helps.

Good luck.
Fred


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Re: Hitachi EX27u Low Pressure ?

Post #5 by le.maisonniau » Wed Jan 17, 2018 9:21 am

Hi Guys,
Thanks for the reply and info, It is going to be dry today and tomorrow here (France), then at least 5 days of rain, so if I get chance tomorrow, I will nip out and have a dig - with the intention being to fully load up a ditching bucket and see what how the m/c responds with blade up down etc.
I seem to have narrowed it down to Boom ram, so it may be prudent to check the supply hoses are air free first :eh:

As an aside, I also bought a new igntion switch to replace the current one that is operated via a screwdriver :thumbdown: needles to say the replacement from "China" does not work :evil: it is very difficult these days to source parts not genuine, even had genuine Hitachi on the box :roll:

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Re: Hitachi EX27u Low Pressure ?

Post #6 by FOWLER MAN » Wed Jan 17, 2018 10:30 am

John,
The ram and hoses will bleed themselves, just operate the ram fully in and out a few times at low revs and any cavitation will clear.
Fred


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Re: Hitachi EX27u Low Pressure ?

Post #7 by le.maisonniau » Fri Jan 19, 2018 5:04 pm

Thanks Fred,
It really is useful getting info from you guys (Experts) :thumbup: I havent had chance to load up a bucket and test the boom lifting potential, hopefully I will have a go this weekend. As you mentioned the rams will bleed themselves (I have given them all a thorough workup especially boom and dipper) then it is looking like a SLRV :dizzy: , so will need my mucca to come over with his test guage, I will need to locate the SLRV too, I do have a manual so shouldnt be too difficult.

The Dozer blade ram is working a treat now - very happy with that.

I also want to give it a run on its tracks and see if I have fixed the squeak/squeal, I have not heard a peep from them in the limited runs so far (inside my woodyard) and I am fairly certain I have sorted it; after finding/replacing a completely collapsed bottom bearing :shock:
Cheers :bow:


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Re: Hitachi EX27u Low Pressure ?

Post #8 by le.maisonniau » Sun Jan 21, 2018 9:00 pm

Update:
Hi Guys, seeing as it was piddling down today (again) I spent the afternoon giving the m/c a good workup.
Ran the engine for 10 mins to warm up the hydro oil, exercised the boom/dipper/bucket and blade with the odd swing for around 30 mins.

The latest state is that: Dozer ram is now 100%, bucket & dipper are 100%, boom is 100% IF m/c is facing forward and over dozer RAM :dizzy:

If I turn m/c around so dozer blade is behind me, AND if blade is down boom has trouble lifting m/c up, if blade is up, boom has no problems and will lift m/c so I get a couple of feet of track off the ground, I can then put blade down and lift the whole m/c level and up a couple of feet off the ground. :thumbup:

I may be imagining things, but performance with boom & blade seems to be improving, at worst I can live with the method of getting the m/c in the air - its not as if I need to be doing this for work. I am quietly confident that it will lift a full scoop under normal ops. Is it possible that there is air at the extermeties of the boom/dipper and are taking a little while to bleed out ? :roll:

It may be a quirk of this m/c, I am disinclined to start fiddling with Valves and such like as a) no idea what I am doing and b) I get the feeling now tweaking valves may be unnecessary :think:

I will still get my mucca across to check system pressures against the charts and see what is what.

Thanks for your input so far guys. :thumbup:


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Re: Hitachi EX27u Low Pressure ?

Post #9 by Jeremy Rowland » Sun Jan 21, 2018 9:08 pm

John I would wait until your friend has tested the hydraulic pressures and take it from there; unless there is a special way to bleed Hitachi machines which I would be very surprised if there was, then I would guess that all the air is already out of the system. It will be interesting to know what the final outcome is keep us informed. :thumbup:

Jeremy


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Re: Hitachi EX27u Low Pressure ?

Post #10 by le.maisonniau » Tue Jan 23, 2018 9:39 pm

Sounds like a plan Jeremy :thumbup:
As soon as it stops raining over here I will get him across with his pressure guage, I have the data sheet so we can take it from there.
Mentioned a while back about a new Igntion key arriving and being faulty, my UK Supplier "Next day'd" a replacement - hey ho, that one doesn't work either, they are looking at the whole batch now. :arrrrgh:
Will keep you guys posted as to progress/solution on the hyrdo pressure. :wave:


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