3ph backhoe hydraulic question

[johneich]

Its a Chinese LW-7 hoe, I have a thread going on this other site, I would appreciate any help from the Brotherhood

http://www.ctoa.net/forum/bulldozer...-to-dig-foaming-out-the-dip-stick-help/#p3379

reply back here, you have to join over there to reply

 

[Matrix37495]

Sounds like its just the one cylinder not getting pressure.... Valve problem or a blockage in the line? You said it was a newer hoe, could there be some trash in the system? Pinched hose? Since its made in china, maybe bad rings in the boom cyl letting oil bypass?

You said it hit 2200psi. I'm guessing thats your main pressure so i wouldnt think its a weak pump.


I'm not sure...just thinking out loud....

 

[Goofyexponent]

If it's anyhting like the dirtbike I bought from china, flush the system out and look for blockages. If you are getting pressure to the rest of the cylinders, then it is not the pump.

Sounds to me like a blockage somewhere or a bad set of rings in teh cylinder packing itself.

 

[johneich]

I am not getting many "reads" on the other thread:
I have changed the oil from w20 to w32 (flushed)

"Valve problem or a blockage in the line"?

"Sounds like its just the one cylinder not getting pressure.... ?"

I swapped out one control valve to another cylinder, (thumb to boom) I understand this is the way to check for a bad valve or bad cylinder, it still did not lift (boom did not still lift with a bucket of dirt, lifted with an empty bucket)?

 

[Goofyexponent]

ok, what about something sticking your relief valve open? That would provide a loss of pressure without a doubt.

Where did you take your 2200 PSI reading at, right at the pump?

 

[johneich]

ok, what about something sticking your relief valve open? That would provide a loss of pressure without a doubt.

Where did you take your 2200 PSI reading at, right at the pump?

Hi, thanks, yes, its plumbed in right after the pump, so I assume that is pushing 2,200 psi all through the system? If the PRV is is sticking open I assume it would never get to this pressure level?

I have gotten stumped on this, it does not leak down, which I think rules out bad cylinder seals??

The boom is lively with no dirt in it, will not lift a bucket of dirt(wet clay)

I swapped control valves, it could be two bad valves?, going to plumb in a third control valve this weekend. I will swap hoses with the bucket and plumb the thumb to the bucket.

I am stumped, I have an OK knowledge of hydraulics, I don't know what to test next...