boom trouble with hyundai 290

[naheed]

just did a complete seal change on the main control valve of my hyundai 290 NLC-7, all went well apart from boom down function.
it works but has lost power and if you boom down doesnt lift the machine off the ground.
but if i do the same with arm out function it immediately lifts off ground.
do i have a wrong pipe somewhere??

 

[John C.]

Sounds normal to me.

 

[uffex]

Good day Naheed
Some occasions this can be a fault of the geometry a simple check you can make to see if this si the case, install a pressure gauge and stall boom down if you have full pressure it is a fact of geometry other wise its a case of fixing low pressure. Boom cylinders are limited by the small surface area of the rod side, this generates much less force than that of boom raise.
Kind raegrds
Uffex

 

[naheed]

nope i recall it would easily lift off the ground on idle!

what pressure should it run at?
about 320 bar?

 

[naheed]

hey uffex you were right it was a simple thing the main relief pressure had gone done, put it back up to 320 bar and problem solved!
think the pressure changed whiled replacing main relief o rings!

cheers and thanks for the help