428C struggling to lift front boom

[Pralhad Birdi]

Hello all,
I've got a Cat 428C Serial No. 2CR03671 that's got an issue with the front lifting cylinders. This issue started a while back, whereby you'd have to operate the bucket tilt to get the front boom up. I didn't pay much attention at the time as it was doing a pipeline trench job that didn't require the front bucket to be used. However, it's been doing some heavier duties lately, and it's gotten to the point where you have to operate the rear stabiliser to get the boom up. I don't really have any good hydraulic mechanics in my area, and the local dealers (Mantrac) would probably charge me more than the machine's worth, so I'm not really tempted to go down that route. Any advice/help would be greatly appreciated.
Thanks.

 

[JL Sargent]

The #1 suspect when this happens is one of the cylinder piston seals. I've never had both sides fail at the same time, but I guess it could happen. Usually one cylinder piston seals fail and that allows the fluid to bypass the piston instead of doing the work.

 

[Honcho]

it could be cylinder or fluid distributor issue. \ suppose I put it right.\ To check which one got an issue? Disconect the hose put a coin to block the fluid passage and bolt it back. And leave over night if it falls, it is the fluid distributor issue, if not, thaen it is the cylinder. Hope you got what I mean, my Eng is poor especially technikal language.

 

[Welder Dave]

If you lift the loader arms up, do they creep down? That would be the simplest test that it is likely the cylinder seals. It could be an issue with the hyd. valve to. I think that's what Honcho was referring to.

 

[Tinkerer]

Honcho !
Your English is better than thousands of people here in the U.S.

 

[heymccall]

If a resolver is bad....

 

[Pralhad Birdi]

Thank you very much for all your responses. I've ordered new seal kits for all the rams on the machine, so I should be changing those this week.
It does creep down when left for even a couple of hours, but the weird thing is there's no excessive outward leakage from the rams. Could be a case of the inner seals having perished?
Also, if the resolver is bad, what is the way forward on that then? Is there any adjustment/servicing, or does it mean replacement?

Thanks.

 

[Tinkerer]

There really isn't anything weird, when the piston seals are leaking and there is no leakage on the outside of the cylinder.
It is quite normal.

 

[Pralhad Birdi]

Quick update:
I was speaking to my dad, and he said this machine brought a similar issue about 12 years back (before my time). At the time, a hydraulic mechanic from apparently got under the machine, changed some tiny o rings, and within about 15 minutes, it was back to normal.
Of course he didn't say exactly what he had done, but does anyone know whether there's anywhere on the machine that such o rings would go, and if so, could it be solved by changing them?
I'm literally clutching at straws here, but I'd at least like to eliminate the possibility before doing anything too expensive.

 

[Honcho]

The only O rings I know of, are those that go with hose connections. Disconnect a hose n u ll see an O ring. If it is the issue seek a hyd oil leak.

 

[Pralhad Birdi]

Not hose o rings, apparently these were tiny o rings. Also, no leakages that I can see under the machine.

 

[mitch504]

I am with HeyMccall on this one. It sounds like a resolver issue, more likely than seals.

I believe that machine has o-rings on the resolvers, that could be it, but I can't swear to it.

 

[Welder Dave]

Does sound like it could be a resolver issue.

 

[Pralhad Birdi]

What would the way forward on that be then?

Thanks

 

[heymccall]

Resolvers are tested by operating the lazy function, and then, while the circuit is still lazy, operate an adjacent function, by looking at the flow chart above.
Looking at the chart, I just can't remember if it is left or right.
If it is a resolver, the lazy function will spring to life when an adjacent function is used in conjunction.

 

[Mobiltech]

Yes there are tiny seals on the resolvers. They can leak internally and cause loss of hyd signal to pump which causes weak functions. The last function in the stack of valves that works right is usually where the problem is.

I’m sure Nige will be along in a bit with pictures.
Also wondering where Mark250 has been. Nothing since November.

 

[Nige]

Here's what the resolver (aka shuttle valve) looks like. This is the section of the control valve for the lift function but the location of the resolver, and the arrangement of it (2 O-Rings & a backup ring) is the same in all of them.
Not an expert by any means but - a stuck ball in a resolver somewhere..?

 

[Pralhad Birdi]

Thanks very much for all the info. I'll get under the machine on Monday and check those o rings.

Thanks.

 

[Nige]

Make sure you also check that the balls aren't stuck while you are in there.....

 

[Pralhad Birdi]

Cheers will do.