Altec boom trouble

A

Afoster91

Location
Cuba city
I have an 87 altec bucket truck. 55ft, not over center. Double bucket, joystick control.
The issue I am having is the upper controls are not working at all, and the lower controls are running the boom by itself. When the purge valve is in neutral the boom still Flys uncontrollably. Altec and 2 other shops have spent many hours inspecting and replacing different valves, switches, and hoses, and are still clueless. Altec says they have never seen this happen before and can only suggest gutting all hydrolic lines and re plumbing everything. Over $10k. The pressure when checked at any locations is extremely high. Fluid level is normal. Does anybody have any suggestions on what the issue could be?
 
Reach said:
Does it have a bad pressure regulator? Engine rpms too high making too much pressure? A bad/stuck check valve or bypass valve in the pump?
Click to expand...
The pressure regulator is brand new, engine rpms are normal, check valve is new. Have not checked the bypass valve yet. Will look into that tomorrow. Thank you.
 
I think you've got a hose somewhere that has the internal lining coming apart, and that loose stuff is blocking the flow. That's causing the high pressure throughout the system which is upsetting everything else.

Finding it is going to be a royal pain. That's why Altec suggested replacing all the hoses and plumbing. The problem material probably came loose at a place that flexes a lot, but there's no guarantee it stayed there, and no guarantee that it won't clear up when you disturb it while troubleshooting and replacing parts only to cause problems later. All the hoses you didn't replace are getting ready to fail in a similar manner, too.

Unfortunately, Altec's suggestion makes a lot of sense with a truck that's thirty-three years old.
 
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