Week Hydraulics

[nick.o]

I'm new to a forum, so please be patient. I have an 89 cat 416 backhoe with week hydraulics. When I raise the bucket ,somtimes it will stop and if I move the control lever a little to operate say the bucket at the same time it will work. the same with the swing on the hoe, all i have to do is move the lever a little over and it will swing too fast, like it is getting to much pressure or volume. I have replaced all the filters changed the fluid and put a rebuilt pump on, and repacked 2 cylinders that were leaking. Not sure what it can be.

 

[Dickjr.]

This happened to my 416 , I was told it was resolver orings. I replaced every one of them and still have the problem. When its cold its fine. I get the feeling its in the swing valve and lift valve as in they need to be completely disassembled and rebuilt. But I need to rig up a pressure test rig and check some things first.

 

[nick.o]

I need to rig up a pressure tester too. Not sure where the resolver is or what it looks like though. Where should I pressure test. Thanks for the reply

 

[Dickjr.]

There is procedure to do the test. There are guys on here that can walk you thru the tests using a pressure gauge. I am an owner operator with enough knowledge to be dangerous about this , I don't really understand how the resolvers work either other than its a signal system that tells the pump to stroke. Most likely that's where your problem is , your not getting signal pressure to the pump. The resolvers have orings the size if the end of a pen that seem to fail. I replaced every one of mine and my problem still persists. I think I may have a line issue between the rear valve and loader valve or the loader valve to the pump.

 

[nick.o]

I guess I'll track down the resolver. How many are there. I'm guessing 1 for each movement on the machine. Thanks

 

[Mark250]

you need to post serial number as the resolver system has evolved with time and there are a few different versions
Mark

 

[nick.o]

Thanks Mark, serial# 5pc08594

 

[Mark250]

h,i sorry for the late reply, from your description it sounds like you have a problem with the resolver network on your machine.
The resolver network is used to signal the variable displacement Hydraulic pump to deliver more flow into the hydraulic system. when you operate a function the primary resolver valve for that function compares the oil pressure between the rod end and the head end of the hydraulic cylinder that is being operated, the highest pressure is then delivered to the secondary resolver valve which compares oil pressure from the other valve section's. this oil pressure which is what we call signal pressure is then delivered to hydraulic compensator valve which in turn causes the hydraulic pump to up stroke and deliver more oil
If you have a faulty primary or secondary resolver valve that signal oil is not delivered to the hydraulic pump compensator valve
as you can see from the signal layout below the resolver valves follow a set order we can use this order to help trouble shoot your problem
if you have a pressure gage rated to 3000 psi and understand the system you can connect to the signal line going into the pump compensator valve and record pressures as you operate the levers
Staring from the left hand stabilizer operate the lever in both directions and note the operation if you have a gage connected note the pressure as well. continue this sequence for all the levers in order including the steering and note the results.
when you come to a function that is not operating correctly operate the next lever in the order at the same time and note what happens
let me know what the results are
mark

 

[nick.o]

Thanks Mark, I'm going to put together a pressure guage, and try to perform the test you suggested. I'll update on progress.

 

[nick.o]

Update, o-rings are missing on the resolver valve. Should be able to complete work soon. While I have the gp valves off I'm going to rebuild entire units. I will keep you updated, thanks for the great info.

 

[Mark250]

glad I could help
Mark

 

[nick.o]

Ok, completely rebuilt gp valves, and i am happy to say hydraulics are working fine now. i had the same problem with the hoe and the o'rings were missing on most of the resolver valves as well. Did this on the machine without removing entire gp valves, now that works great. I finally have a machine that works great, thank you very much for the help, you nailed it.

 

[nick.o]

Ok, so having a similar problem with hydraulics. I have been using machine without any problems until yesterday. i was moving some stumps with the clam and lifting them up to move. one was fairly heavy, and it moved it fine, but shortly after that all loader, clam, lift and curl barely work at all. The hoe works fine except the swing seems slow and stabilizers. Any help would be appreciated.