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Hitachi EX 300-3 Hydraulic problem

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DanJanMan

Member
Joined
Jul 29, 2013
Messages
5
Location
Weymouth MA
My EX 300-3 has a control lockup up problem that has me. When cold, my rear pump will lockup and I will lose a function. Usually it it one track or a boom up issue. When I turn the machine off and restart, all is back but will happen over and over until the oil warms up and frequency reduces. When this happens, the pump will squeal. and the main line from the pump to control valve, which gets totally pressurized, feels like it if filled with buzzing bees. All of that stops after a restart.
I did previously, replace an o-ring in that regulator to stop a leak and fear I may have started the problem then. Any help with this is greatly appreciated.
Dan
 
P

pfpm

Member
Joined
Nov 4, 2011
Messages
24
Location
Australia
When cold some pumps get valve plate to slider separation which is why your track stops completely. Some only do it when hot. The vibration you can feel when hot is the same thing only at a higher frequency.
When these machines first started showing these symptoms Hitachi would replace the valve plate and head only and this seemed to work. This was done with the pump still on the machine, pull a vacuum on the hydraulic tank and off you go so it only took about 1/2 hour from memory.
Try idling the engine right down without pulling any levers that sometimes brings the pump back together.

Mike.
 
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