Hello Everyone, I've have CAT 345BL machine which has a problem with dipper stick cylinder retract motion, it is slow and powerless. In fact, strange thing is that it is not all the way slow, at the end (near to horizontal) it retracts fast, as expected. Also when it is released from fully extended (cylinder) position (Bucket is near to cabin) until vertical position, the movement is fast. The main issue starts after the vertical position of the dipper stick. It moves slowly and during this period, we can hear the noise of hydraulics. All the other motions and power of the machine is good. There is no such slowness issue on Extend Motion of the dipper stick. There is no any drifts observed nor any leaks from this stick or any other boom etc. Dipper Stick Spooler and Drift Reduction Valve checked, are OK. Dipper Stick Ram Return and Pressure line hoses are switched and checked to see if the issue is due to the spooler. At that moment, we expected slow Extending motion of the cylinder and fast retract Motion. However, it came out to be vice verse, still the issue was same, slow motion while retracting (fast extending) although pressure and return lines were switched. We have checked the Dipper Stick Cylinder, Piston is not scratched, looks OK. Sealing look good as well. There is no any trace on the piston that it had some restrictions inside the ram. The strange part is no one has seen such cases before that's why i though one you guys have some advice. Regards, Annaly
I think the snubber has come off the end of the rod and stuck in the end of the cylinder. It slows the last bit of travel to prevent cyl damage from banging. Later Bob
check the make up valve. They can give you some problems.
Thank you Bob and owmamech! Let me check those and will update...
Take the hose off of the back end of the cyl look into the port and see if you can see a sleeve(the snubber) inside. If it slips inside the cyl take cyl apart don't use power on it or cyl could be ruined. Later Bob
Did you also pull the regeneration valve and check the seals on that? It's the one you get to from beneath the main valve straight up inside a 4bolt square cover. Very common to have the seals dissappear totally on that causing all sorts of weird problems.
We have checked the port of the rod end cylinder, no snubber in there, it is clean. Looks like it is in its place because it is not either inside of the cylinder.
Good point! No, we haven't tried but will do it today or tomorrow and check.
You better look again. If I hear you right the problem didn't change ends when you swapped the hoses. That points to the cylinder as I see it. Later Bob
Yes, you are right. Problem did not change although swapping the hoses. We can feel the snubber inside the rod end but port looks not obstructed. However, we will check it once more in detail. Does it can be due to the belled cylinder? Becuase the retract motion is fast at the end of retraction but if this is the case, extending motion is supposed to be slow as well.
That is possible although I have not seen that problem since the 235 was first introduced. If that happens the piston seals will blow apart and it will drift all the time. Later Bob
Where is this noise you talk about coming from? Pumps, cylinder, valve..... etc. Boom and stick functions are 2 pump functions meaning both pumps should stroke up when in use. Both functions also have two valves each. So if on valve is not opening all the way it would cause slow cycle time. I would also check cycle time on all functions and make sure the pumps are flowing normal. If you find slow cycle times or a valve sticking, cut your filters and make sure you don't have debris in the system from failing pumps.
Did you check to see if the piston is loose on the end of the cylinder rod? Doesn't take much for oil to bypass between the two. I have seen one cracked and just about to break off.
Sorry for the late reply. We took the cylinder apart, checked the port and inside ram. Snubber is in place and is not obstructing the port. Piston and seals are in good condition, no scratches or any damage were observed on the piston. Looks like it does not seem to be due to the cylinder. We will going to check the Regeneration Valve and will update accordingly.
Noise starts when the stick is starting to go up and coming from the hydraulics line. It seems like a noise of flowing hydraulics within the pipe etc. It is not coming from the pump definitely. 2 Pumps are working fine because all the other functions of the machine is perfectly working. There is a problem with Stick retraction only. It looks like not enough hydraulics is delivered as this may produce a flowing noise. However, we swapped the hoses (pressure and return line) of that cylinder, still issue is the same. Also, filters have been checked and cleaned, no significant debris accumulated inside.
Yes, piston has been checked, it is not loose. It is stiff in place. No traces of mechanical contact on the piston, it is shining as a new.
What you might try is put it back together and start the machine cold, move the stick till you hear the hiss, then shut it down and start feeling lines and cylinder for any warmth. Where it is warm at is where you have a restriction. You might have to take the control valve apart to see if one of the centering springs is broke, that would let the valve only open up so far. because a piece or a cap is jammed in not letting the spool travel far enough to get full flow of oil. I have seen this only one time and that was probably 25-30 years ago. Did you try switching the joy hoses at the valve. to make sure the problem isn't in that part of the system? It sounds to me like you have gremlins in there, I hate when that happens. Good luck Maurice
Thanks for the quick reply. Yes, sure. I think tomorrow we will put the cylinder back to machine and will try to check what you have advised above as well. Yes, we did swap the joystick hoses but it didn't help. I think pilot system should be working fine. Regarding the Control Valve check; if something is jammed and spool can not travel far enough, this would also affect the Extending Motion when swapping the hoses of Pressure and Return line of the cylinder, right? However, Extending motion was not affected at all, working fine but still the retract motion did not change. Regards Annaly
grannaly take the long tube off of the cylinder and check it for obstructions. Later Bob
And how about the regen spool, checked the seals on that yet? i'm willing to bet some money on it.
Why did it not changed when thy switched the hoses on the cyl. ?
Depending on where you swap the hoses at you might have a bad hose on the inside. May have swallowed it's tongue. You sure have a good one there! Will be interested in what you find.
Now, it is time to check, rest of the systems were checked, nothing has been found yet...will check the regen spool soon, slowly coming down to the root
Yes, exactly this is the question everyone is concerned actually Looks like this is an odd issue though
We swapped the hoses on cylinder end. Hoses have been checked separately, both of them are good, no obstruction inside.
Bob, we checked it, clean
I think you are not getting both pumps to upstroke when swinging stick out. Its fast when gravity is helping bucket away from cab but when you go over center only one pump is filling cyl.
Gents, We have checked the regeneration valve, all the seals were extremely damaged, no sealing function was in place. I will post the pics tomorrow. Thanks Per, we are not 100% sure yet but looks like this is the root cause for the issue. After installing redressed regen valve and cylinder, we will check the machine functionality and update this thread. By the way, we saw that there were some tiny metal particles inside the valve, does these metals make the seals worn out? and is there a best practical way to clean the whole hydraulics system from these particles?
I don't think it's related. Replace filters, make sure tank is clean and if you have one, run a kidney loop.
gannaly, the regeneration valve is common to be called the recycleing valve (spelling ???) in the U.K. it is a bit of a pig to strip out due to the oil dripping all over you as things come loose, credit to Per Eriksson for chiming in at the start pointing you to this valve that often thows up some very odd antics with the front end activity, anyhow things should be better now with a few penny 0 rings etc stuffed on to the shiny bit with groves, to do a half good job on the hydraulic tank and oil clean up, I use my kidney pump to pump out the hydo oil into clean barrels or I.B.C. container, then do all the filter and tank cleaning dutys, finaly pumping the oil back into the tank useing the kidney pump, so the oil has been filtered out and then back into the tank so things start off from a good point, oh and just a point, the spool springs are under the top cap, remove this cap and the spools lifts out, tctractors
We have tested the machine after installing the regen back with o-rings dressed. Unfortunately, issue has not been solved yet. Old o-rings on regen valve were completely worn out, there was no any o-ring in place but only tiny hardened o-ring particles instead. That's why, may these old o-ring particles spread over in a hydraulics system blocking the flow to the stick? If yes, where should be the first place to be checked?
You would want to start by tracking the lines down stream from the regen valve,and anything going to the slow moving cylinder.Had this happen on a trencher and the hydraulic tank was full of packings and the suction screen was covered with packing restricting the flow.The hydraulics run hot because of this.Good luck.
Based on the reply above why not pull the suction screen out of the tank and check it as a first step ..? It's easy enough to access.
Can you cap off pilots and run stick from one pump at a time, that might isolate it to one section.
Does it track straight?
Any update?
Sorry guys. Due to the weather condition, we are currently stand by. We will update once we again start trobleshooting. Yes, it does track straight, no problems with tracking. We are planning to check 2nd pump's connecting spool for stick.
I have seen a lot of the regen valves fail. There was a service letter on them from Cat for the 345. Rather than resealing I would replace both. They will seal ok with no load but when loaded they leak which shows up after the downward travel of the stick. I can't explain why swapping hoses didn't work but the regen valves do connect both ports in regen mode. When you had the cylinder apart did you pull the nylon seal out on the piston and check the oring underneath it. Sometimes that oring can fail without showing signs on the outer nylon seal.
If what you tell me about swapping lines and the problem staying the same is correct, I will repeat myself once more. " Check the Cylinder or get it rebuilt" you are missing something. Later Bob