Hello all again. Now i have a problem with my Cat 426 Hydraulics system. Again!. This is a 1987 Cat 426 SN TBC00580. Problem is the front bucket stopped raising yesterday. Started out (since i bought it) that when i would try to curl the front bucket and raise it at the same time the engine would bog down and die. Then i stopped doing that and i would curl and THEN raise it and it got very slow and then stopped raising at all. By the way, the engine will bog down and die on some of the other control handles as well. If i try to use the backhoe to curl and raise it will kill engine too. None of the hydraulics have worked very well cause the unit was junk when i bought it. But it has worked well enough for me to keep working it. Not just very well. The cover is off the area where the front bucket control handle is and i can see the spool and see the valves move when i work the handle. I can also see there are adjustment linkages there and maybe they need adjusting? Problem is i don't know which way to adjust. Maybe someone there can tell me what i can do to fix it.? All help is greatly appreciated.
Not familiar with Cat TLB's but have read on here about resolver issues where the hyd's. won't function. Someone familiar should be along shortly or you could look in the archives.
Too many big words in that post for me, but I saw "bog" and "die". the first step is to determine if you have a problem with hydraulics, or low engine power. Does the engine blow some black smoke when it bogs and dies? at least some visible smoke, probably dark. Does the backhoe blow black smoke if you try to climb a hill in road gear?
No. It just bogs down and dies immediately. It only happens if i try to invoke left anf curl at the same time. Almost like the system reached a total blockage. I have heard of this before but do not recall any specifics on it. Also, i have searched on the net and not found anything related to this. I might be using wrong search words?
Look on here under resolver issues or something like that.
OK. I did that and nothing i could make sense of and use was there. Of course i am not experienced enough to recognize useful info when i see it. LOL I will keep looking. One thing i need to point out is the bucket will NOT lift with a load on it. HOWEVER, it WILL lift with no load. With no load it will lift at the normal rate which leads me to believe that the fluid is somehow bypassing?? I don't think i mentioned this in the original post.
Ok. Another thing i should mention is i actually was able to adjust the pushrod on the lift control. It has a fork that can be adjusted in or out and i adjusted it out for more length. That would cause the plunger thing to go further in the control and the results were zero. It had no effect at all. Maybe somebody can shed some light on this adjustment feature?
I don't think you looked too hard. This is one of several threads dealing with a resolver valve issue. 428C struggling to lift front boom | Heavy Equipment Forums
Not me. I wouldn't touch any adjustments. If it was sort of working before, it didn't go out of adjustment. Resolver issues are common as WelderDave mentioned. If you don't understand it, find a hydraulic manual, especially a CAT one. I won't touch that because that's not my wheelhouse. I EXPECT to see smoke when an engine bogs down, IF you don't see smoke, then I EXPECT the engine is starving for fuel. Can you get it to blow smoke by lugging the engine down climbing a too steep hill in too high a gear?
I lug it down all the time and have never seen dark smoke come from it. I have seen other tractors that produce dark smoke and strain like crazy. But my tractor only lugs down and if i don't let up on what i am doing at the time it just dies. Fact is it will not rev up very high at all. Tach is broke so can't say for sure what RPMs are but i know they are not high. I often wonder why but because it works, i just leave it alone. I never knew what a resolver was until i saw the pic of one here and it is also called a shuttle valve? It looks pretty simple and been trying to find repair kits for mine, but no luck so far.
You made a small error in the Serial Number of your machine, it's 7BC00580 not TBC. Not surprising seeing as no repair kits are sold., only individual parts. The resolver seals have been updated to add backup rings behind all the O-Rings. See attachment, it has all the Part Numbers you will need to reseal the resolver valves. Whatever the quantities listed, multiply them by the number of sections in your control valve assembly and that's how many you will require. When you remove each resolver make sure that the ball inside it rattles proving that it is free to act as a shuttle valve. If you find one where the ball is stuck it will need replacing with a updated Part Number (also in the attachment). If you read through the thread linked in post #8 above it has all the information you need to reseal all the resolver valves.
I would look at your fuel system before looking at the resolver valves. The fuel system is fairly straightforward, fuel in the tank has to get to the injection pump. if it gets blocked with dirt, gravel, bugs, plastic, foil, tar, water, slime and can't get to the injection pump fast enough, then your engine won't have enough power. The dirt gets trapped in fittings, screens, collapsed rubber hoses, filters. Take it apart and clean those, or use a pressure/vacuum gauge to watch the fuel pressure going to the injection pump, or run it off a temporary tank to see if the hydraulics work different with better fuel supply. A diesel engine of that age should not die without blowing visible smoke as it's lugging down. I'm not saying your hydraulics don't have problems, but the engine needs enough fuel to make smoke before you can judge the hydraulics.
If you bottom out the control that is next in line to get oil and the bucket raises its a resolver but from what you are saying it think you have a pump issue the pump is not unloading thus stalling the engine. You have to work both controls at the same time for this test
Great. Good information. Glad you confirmed the kit is not available. Going to look outside El Paso for the o rings etc. There two valves there that operate the bucket. The one that raises the bucket is the bad one. The one that tilts and curls is operating as it should. There is a video on utube that i just looked at, that addresses my exact issue but his is a 416 which appears to be exactly like my 426. He demonstrates in detail exactly how to replace all the relevant o rings etc. Appears he got the parts from a Cat dealer. I will do the same.
Would you please post a link to the video. Thanks.
Ok here is is and he has a second one a year later on another problem: Backhoe Hydraulic Repair - Loader Does not Lift - YouTube Post number 2: Backhoe Hydraulic Repair - Loader Does not Lift Part 2 - YouTube
His would not raise, yours stalls the engine. Those are not the same symptoms. I'm not a Cat guy, but everything that mentions the resolvers, has one function not raising, until you operate another function and then the first will operate. That is a different issue than one function stalling the engine. I have not heard of that being a common Cat issue.
Possible multiple issues to deal with. I just remember reading about resolver issues.
Just to bring you all up to date on my progress. I was able to get pics of front bucket hydraulic valve cluster. It is a 2 circuit set because i do not have the "clam" feature. The functions are TILT and LIFT. The lift function was the bad one as it would not lift a load. So today i got the time to dive into it and took tilt part cap off and underneath it was the primary Resolver. It DID NOT have a single O Ring on it!! Apparently they had all deteriorated and washed away. By now they are probably in the inline filter. I will post more pics as i go along. My plans are to replace ALL primary and secondary resolvers in for the front bucket and the backhoe as well. Have ordered all of them online and at a very good price.
OK. Pics did not come out very good so will try again. So much for that. Will try later.
Good that you found the problem. Did you give the resolver a shake to make sure the ball inside it is free to move.? If the ball is stuck for some reason (e.g. jammed by a bit of old o-ring) the valve will not function even with new o-rings installed. The idea of replacing all the o-rings on all the backhoe functions is a good one as they are probably in a similar condition. The machine is 35 years old, I imagine the o-rings are the originals.
Yes, old machine and i would guess it is all original stuff. I have ordered the entire set of primary and secondary resolvers which include the new revised ones that Cat came out with. There are 8 total and after watching the video by the fellow who working on a 416, it looks fairly easy to do. The new version of the primary ones (By Cat) have an extra "backup" O Ring on them. One thing i am concerned about and maybe you know the answer , is taking that next "cap" off to access the next primary resolver in the lift function. If you will look at the first pic i posted where i have the first cap off that has the solenoid on it, right next to it is a round cylinder. That cylinder has 3 allen head bolts holding it on. My question is what happens when i take those screws out? The manual i have shows it all broken down but i don't know if it comes off as a unit or all the little parts, springs and ball just fall out when i pull the cylinder off? Looks like it could be a disaster for me if it falls apart. LOL