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.
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.
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.
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.
Honcho ! Your English is better than thousands of people here in the U.S.
If a resolver is bad....
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.
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.
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.
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.
Not hose o rings, apparently these were tiny o rings. Also, no leakages that I can see under the machine.
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.
Does sound like it could be a resolver issue.
What would the way forward on that be then? Thanks
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.
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.
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..?
Thanks very much for all the info. I'll get under the machine on Monday and check those o rings. Thanks.
Make sure you also check that the balls aren't stuck while you are in there.....
Cheers will do.
16 & 23 are both resolvers.
#23 was my issue on a previous machine doing the same thing. Orings blew out.
There's a revision...also cross section pics to help visualize.
And, nothing says that you have to update to the revised parts...you can just rering what's there.
Nige, could you please give me the part number of the valve in the picture, as I want to get the o rings from the dealer before removing the resolver. Thanks very much.
Heymccall, sorry just saw your post. That's brilliant, thank you very much.
The part numbers I posted are for the UPDATE, which has new resolvers and seals. If you're just resealing yours, you'll need different part numbers.
I do plan to reseal mine. Would it be possible for you to send over the part numbers? Thanks
I do plan to reseal mine. Would it be possible for you to send over the part numbers? Thanks
It's somewhat weird. The Service Mag posted above by HMC is dated November 1999. The OP's machine was built in October 1997 yet searching under the complete Serial Number in SIS lists the updated parts........attached file. However, and it's not clear in the Service Magazine article, out of all the Part Numbers ONLY the three hbackup rings (4T-7807, 126-5984, & 126-5985) are "new" inasmuch as before 1999 they were not used on the former 4T-4525 & 4T-4526 Shuttle Valve Assemblies. All the O-Ring Part Numbers, and the Ball, remain the same. I think if it was me I would remove one of the shuttle valves and check if it has backup rings installed on it. Then you know whether to order them or not.
Bit of an update: Opened the resolver at the bottom of the valve, the o rings were okay, but the ball seemed stuck. Unstuck that, put it back. Then I opened the smaller one on the side (very accessibly located) and the half the o ring was missing. Replaced that, put it back, started the machine, but there was no difference. Then I opened the bottom resolver for the bucket tilt valve, and the o rings in that were okay, but the ball was stuck as well. So I unstuck that and put it back. Tried to open the one on the side, but the allen head slipped. So I started the machine, and now when you operate the bucket tilt and boom lift together it lifts the boom, and when you operate the boom lift and bucket tilt together, it tilts the bucket. So it's definitely better than it was, but I'm suspecting the second resolver on the bucket tilt. I'll have to remove the whole valve assembly to get access to that so it should be a fun job. Anything else that I could try, or is the resolver the main suspect?
If you’re finding the balls stuck I would think that means the ball seats are worn out and the ball will likely jamb again. I would recommend ordering the complete resolvers. A tip on removing the Allen plug resolvers if you can get at them with a punch slightly smaller than the head of the plug give it a rap with a hammer and then try using the Allen wrench to take it out.
Thanks for the tip Mobiltech! I've also ordered a hydraulic gauge test kit, because a couple of people have messed around with the pressures on this machine. The only problem is I've never really done any hydraulic pressure testing. What would the basic process be, and what sort of pressures would I be looking at? I want to use this machine to gain some experience, then I hopefully won't have to rely on outside contract "mechanics" who don't really know what they're doing 90% of the time, which is quite a common problem in my neck of the woods unfortunately.
Extremely late update: The culprits were the resolver o rings, all of them were gone on the upper resolvers of the front control, and all 14 on the backhoe controls were gone as well. Changed them out and it's back to normal now. Would anyone be having the test and adjust specs for this machine? Thanks
You mean for the hydraulic system..?
Yes for the hydraulic system.
Here you go. Question for you back to the discussion on Page 1. When you pulled out the resolvers, did they have just O-Rings on them or did they have backup rings as well.?
Thanks very much Nige! They had just the o rings. Well what was left of them anyway. No back up rings.
Did you install the backup rings..? I think I would have.
I didn't, but now that you mention it, I probably should. Will do.
If it didn't have the updated parts, the grooves would be too narrow to fit backup rings.
Good point. Just because by Serial Number SIS shows the updated parts doesn’t necessarily mean that the machine was actually built with them. Just out of interest it might be an idea to pull one of the easier-to-remove resolvers and see whether or not the backup ring will fit in the groove.
Yup, visual verification. The only sure way. As an aside on serial number breaks.... I had a 325CLCR, BKW00334, with 3200hrs, shear the hydraulic pump input shaft, which I've never seen on a working pump. Turns out that there was a bulletin covering BKW00001-BKW00328, so it "supposedly" didn't apply. Turns out that several components were mismatched to the setup, including the balancer (damper?). Ran with new pump and updated parts until she burned a hole in a piston @ 9k hours (injector failure).
Yep the grooves are too narrow to fit the back up rings. I suppose I'll just have to have a few o rings on standby in case it ever happens again.
Hello Nige. My name is Clifford Baxley. I just joined this forum but i have seen and read a lot of your answers. I am working on a 416C Cat backhoe. I changed the hydraulic filter and afterwards the steering has been giving problems. The only way to get power assist is to raise the front bucket to its highest point. I talked to a Cat tech and he told me there was not anyway to bleed the system. It seems like that is the problem but i don't know. If you could help i would appreciate it very much. Thank You
You might want to make a new thread and then the whole group of HEF members can see if they can offer any assistance. Nige is very knowledgeable but maybe not quite as much as some others on the smaller equipment.
He did start his own thread. He has a stuck or bypassing resolver.
All the answers you need are on Pages 1-3 of this thread. As HMC said on your earlier posting in another thread you have the classic symptoms of a resolver valve sticking. Take them all out one at a time and reseal the lot is my suggestion. If you want help regarding confirmation of Part Numbers for seals, etc, I suggest that you post a machine Serial Number on your other thread.
Didn't realize he made an earlier thread. Saw his post and thought he was only looking for Nige's help and thought others could also offer assistance.
hi under need the TLB bei the rear rigth wheel in front of the rearaxel boltet into the chassie is a valveblock with a pressure setting rod. lossen the looknut and turn the rod in a quatter or half a turn. look the nut again not do hard and work the tlb. noemaly dat das the trick. i am sure dat is wath your mech. has done. good luck.
Adlif, is this the valve block for the front bucket? Can you post a pic of that adjustment rod? Thanks