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I have a tachi ex270lc and we recently replaced both of the

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I have a Hitachi ex270lc...
I have a Hitachi ex270lc and we recently replaced both of the main hydraulic pump due to the old ones leaking and loss of hydraulic power. Once we got both pumps on we took it back to the work site to find we didn't have anymore power. We check both pumps and only had 2000 psi. We then took the pressure valve and turned it down as directed by the Hitachi tech. It took it up to 2500. We then talked to a guy who rebuilds hydraulic pumps and he told us to turn the fins of the pumps to gain some pressure. We did that and it brought us up to 3000psi. But it still doesn't have enough power to do what it needs to do. But it will pull the motor down under pressure but yet will barely dig. We have asked hitachi and others and they can't come up with an answer we are just trying to find any answer we can.
Submitted: 2 years ago.Category: Construction and Road Equipment
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Answered in 1 day by:
11/3/2015
Mechanic: Dan, Technician replied 2 years ago
Dan
Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 5,703
Experience: 17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
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Hi my name is***** will be glad to try to help. What is your machine serial number? Also check the return filter and pilot strainer for signs of fine metal and let me know if it is present indicating contamination of the system. If found the system will need to be thoroughly flushed. Remove and inspect the main relief valve cartridges from the main control valve and clean and inspect for debris causing them to stick open or damaged o rings causing a bypass of pressure. Also replace the o rings as well. Let me know the results and if wee need to dig deeper.

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Customer reply replied 2 years ago
Hi Dan
The serial number is(###) ###-#### ***** we had the pumps off we flushed the system and checked and replaced all filter and put new oil in. The filters and tank were clean of any debri or shavings. We also had the valve out and inspected it previously and put new o rings on it and stripped it apart and found no shavings or debri so we put it back in but it didn't change anything.
Mechanic: Dan, Technician replied 2 years ago

Thanks for the update. Is this a dash 3 or dash 5 machine, etc?

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Mechanic: Dan, Technician replied 2 years ago

Do you have the service book for this machine for the testing and adjusting and specs? Here is one available online for immediate download depending on the series you have . https://www.tradebit.com/filedetail.php/207389014-hitachi-ex270-ex270lc-excavator-service-manual

You will need to check pilot pressure, pump signal pressure that controls the pump output flow, and your relief settings that it sounds like you already have tried setting them. If the pump is not stroking to full flow then either it is low on signal pressure, a control valve/servo problem, or a problem with the pump itself. Is this a rebuild or new pump?

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Customer reply replied 2 years ago
It is just a plain ex270lc. And both pumps are rebuilds but both were checked before shipped and tested fine. And they put out the same pressure as each other whether it is boom or travel. We had tested the pilot pressure earlier and it was were it needed to be. And the relief valve is set to put out its maximum pressure.
Mechanic: Dan, Technician replied 2 years ago

Thanks for the update. If your signal and pilot pressure is in specs but pump output is low there is either a calibration issue or another issue with the pumps. If you do not already have the manual I recommend downloading the one in the link I posted and running through the pump adjustments and on machine calibrations. Some of those you will need a flow meter which are very expensive but for a one time use it might be a good idea to have a hydraulic shop or dealer flow test the pumps for your to confirm the GPM output of the pumps. I would not rule out that there is a problem with the rebuilt pumps. This is what it is pointing too

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Mechanic: Dan, Technician replied 2 years ago

I have seen this happen on many occasions with some rebuilders

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Customer reply replied 2 years ago
Ok we will run through things again and let you know what we find out. And we have a tech manual for it. So we can get the procudure out of it. As soon as we get through it I will let you know what we come up with.
Mechanic: Dan, Technician replied 2 years ago

Sounds good. Unfortunately they are not likely going to volunteer that they made an error or calibrated the pumps incorrectly. Let me know

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Customer reply replied 2 years ago
We are waiting on a sensor for it once we get it and check things out again we will get back with you and let you know what we found.
Mechanic: Dan, Technician replied 2 years ago

thanks for the update. I look forward to hearing the results

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Customer reply replied 1 year ago
We got the sensor put it on and ran the excavator. It seemed to give it more ump but still are only putting out 3000psi. But it will kill the motor. Also we checked around and no one will allow us to borrow a flow meter to do the tests. Just wondering what your thoughts were.
Mechanic: Dan, Technician replied 1 year ago

Thanks for the update. I recommend flow calibrating the pumps on the machine to see if they can be adjusted into specs. Flow meters are very costly unfortunately and not something shops will usually lend out. Have you been in contact with the shop that rebuilt these pumps? The liability should be in their hands to get these pumps functioning properly and calibrated. What warranty did they give with the pumps? Id argue for them to cover the expense to have the pumps set up properly.

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Dan
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Category: Construction and Road Equipment
Satisfied Customers: 5,703
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Experience: 17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.

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