Boom down randomly becomes weak when warmed up - John Deere 490e excavator

[joelx777]

@

What did I miss? Did you test that valve? Valve was junk? If you don't feel good with a part like that, do NOT use it! The consequences are huge! I think I might have fought harder to repair the old valve. Maybe someone does that? Springs have spring rates. They are progressive and very easy to test and determine. I've seen many springs with micro cracks, like valve springs. When a spring test is run, they fail it.

Anywho,

I put the new valve on and took the old valve off - I would like to find someone to repair it or find specs for it so I can repair it myself. Any recommendations?

 

[joelx777]

@fastline @mg2361 @excavator @Jason Klassen @Diesel Dave plus Matt from the Pacific Northwest Hillbilly youtube channel - Thank you all so much for helping a stranger out on the internet! I have fixed the weak boom down issue now. The root of the problem was a failed circuit relief valve. I swapped it from the boom down function to the bucket dump function and the problem followed it over there. Today, I replaced the faulty circuit relief valve with a new one and it now works perfectly. I operated it for an hour and got the machine good and hot and the old weakness issue did not return.

I will start a new thread soon for the next issues I want to work on:
-Possible overheating? I ran the machine today with the new valve in place and the control valve got up to 160 and previously with the old valve I'd seen the pump running 10 degrees hotter than that at 170.
-Fixing where the battery panel has rusted through - check out this ugly rusted through plate under the batteries. I don't have any welding equipment and don't know how to weld yet. I do want to learn but space is low currently for me in my garage. What should I do for a quick but effective fix here?

 

[Jason Klassen]

As far as the pump, it never fully destrokes. With the levers in neutral, the pump will maintain approximately 24 degrees of swash. This is where you need diagnostic equipment so the pump displacement angle can be checked and properly adjusted if necessary.

Sorry mg2361, a small correction if I may... 24 deg is the max pump angle.

At idle with the control levers in neutral the pump angle should be 3-5 deg.

 

[mg2361]

Sorry mg2361, a small correction if I may... 24 deg is the max pump angle

Oops! You are correct, I mis-wrote. Thanks for the correction!