I recently bought a 420D IT TLB for digging ditches and widening a logging rd into our future homesite. It has been doing great and I'm nearing completion. Yesterday the stick started slowly dropping on it's own. There is a leak on that cylinder either at the seals or connection or some of both. When getting the hoe extended completely out so I could grease all the zerks...I set the bucket on the ground with stick and boom fully extended and it started to draw back or dig in a little with me doing nothing. For consideration; There is a leak at one stabilizer. It mainly leaks when I leave it down as a parking brake overnight. There is a leak on the boom cylinder and the stick cylinder. I talked to a grader friend who says it's the valve body. Another friend says I have air in the system because I just had to ad 2 quarts of hyd fluid after working it for a few days and then letting it sit for a week with the leaking stabilizer down. I have no ideas due to no knowledge of hydraulics... I'd appreciate any help greatly. Thanks, Daniel
It's probably in the valve body under the cab at the rear of the machine but I'm no mechanic either. My '03 420DIT is sluggish with low power swinging left, no cylinder leaks. I'm assuming it's in the valve body from talking to my Cat dealer.
Thanks for the help. Still eager to hear any other guesses.
you really need to post a serial number there are too many differences between models. is it pilot control or mechanical ? mark
Here ya go. It has pilot controls and serial # is BLN05489
You say there is a leak at that cylinder, is it leaking enough to allow the cylinder to move?
That's a good question. I told my grader friend about the heavy leak at the stick cylinder and asked him if that could be it. He said he did not think so. It's weird that I can still use it although it does seem like it is weaker at digging. even weirder is that if hoe is placed on the ground it keeps wanting to go down as if digging on it's own. It only does that ( after letting go of controls) for just 3-4 seconds and stops.
The cylinder is moving on its own due to internal leakage past the piston from the rod side to the side with more effective area. Have the cylinder resealed.
are you saying that the stick is moving on its own or the boom is moving on its own or both
Leave the bucket a few inches above the ground, shut it off and see which one moves!
Sounds like there's air getting in the system which compresses causing the movement after you release the valve control.
thanks for trying to help all... I used it today to clean out a ditch about 300' long. When using it I don't notice any problems. When I swing the hoe to dump dirt and then swing back there are no issues. It seems like the stick only drops if am stationary and not using any other controls. I used 2 cans of brake cleaner to clean up the area that seems to be leaking. After 3-4 hrs of use I took a look and it was wet with new hyd. fluid. The cylinder that raises and lowers the stick has two hoses. 1 at the bottom and 1 at the top. The top hose is steel for the last 2-3' and the leak is right where it attaches to the cylinder. Just wondering...is that cylinder end where the hose attaches a check valve? Another note is that the seal where the rod comes out looks rough. I actually thought it was spanner type nut due to chunks missing here and there. The cylinder in question is leaking from one end at the hose connection and the other at the rod seal. Can I like someone suggested just chalk it up to bad seals in the cylinder?
Air in the system is a possibility but I would think the pump would be quite noisey and all cylinders effected by gravity should do the same thing if used enough. When a cylinder leaks oil at the rod seal it also brings dirt into the system every time the rod moves in so I would think you would want to reseal it just for that reason.
Where the rod comes out is a wiper to keep trash out of the seal. If the internal seals on the ram are damaged you'd have no power for working if the cylinder worked at all. .
I believe he said it's weaker than usual which could be an issue with a resolver valve, line relief valve or cylinder!
Well...Yesterday, I used my backhoe for about 4 hrs digging a ditch. The dipper/stick would slowly drop if I wasn't moving side to side. If I just raised it by itself then it would drift down. Today I went out to finish the ditches. It was fine at first but after about an hour I noticed that it was getting slower and dropping/drifting at all times. Eventually I had to stop working because of the weakness in the dipper. All other cylinders are acting like normal. Now the dipper will not raise and makes a sound like air escaping. kind of a chssshhhh sound every time I actuate the pilot control forward to lift the dipper. If I let it cool down for a bit then I can eventually get it to slowly raise but it drops very quickly then won't work at all and just makes the chsshhhh sound. Any ideas with this new info. Thanks guys
It's time to take the cylinder apart!!!!
While waiting for the mechanic to show up and better evaluate the situation I'm thinking about changing the hydraulic filters. From what I can tell there are 2 filters. One is near the engine and says hyd. filter. The other is further back towards the rear axle and is large. There is a napa gold filter there and says hyd power filter. I have a tattered owners manual and from what I can decipher it sys to turn on key but not crank. Then it says to move all controls back and forth and side to side to relieve pressure. Next just remove old filter and install new one. It also says they have a valve that keeps fluid from draining when replacing filter. My questions are does this sound right? Do I fill filters with fluid before installing? This is a 2002 Cat 420D IT 4x4 serial CAT420DKBLN05489 Thanks Daniel
From what I can find your machine shows two filters 126-1817 or WIX 57084 with 1 micron rating flow rate 32-34 GPM 134-3014 or WIX 51733 with 12 micron rating and flow rate of 28-30 GPM For NAPA filters there is a 7 placed in front of the WIX numbers. WIX makes filters for NAPA As for the shut off valve, don't know but look above the filter on the housing and see if there is something which rotates
The procedure is correct, I would not fill them before installing and I would ask the mechanic to cut the old filters open to see what's in them!
Thanks for the information. Today while using it the dipper moved straight out on its own and would not retract until I turned off the key and relieved pressure. Does that still point to a bad cylinder?
I would think the spool valve would need adjusting, but these others guys are more of then expert Have you checked your fluid level (level ground, buck flat and down, riggers up, boom up and bucket tucked in)?
Yep. And fluid right at full mark.
you could have residual pilot pressure acting on the end of the spool does the joystick feel looser than normal, if so the pilot control valve plungers may be sticking or if the control is not adjusted properly it could be holding the plunger down and allowing pilot oil to the stick spool. it is also possible that a spool centring spring has failed in some way Mark
Did it sound like there was a load on the engine before you turned it off? How did you release the pressure? When restarted did the stick work normally or did it drift out?
I relieved pressure by not cranking but just turning the key and actuating all controls in each direction. After doing that the dipper/stick started to fall from the fully extended position. I have someone that wants to rebuild the cylinder Monday. I'd hate to rebuild the cylinder and find out it's something else. As far as hoe pilot control, it does feel a little different than my right side control. Occasionally, over the last 50 hours, the left pilot control would bind a little when pushing forward to raise or lower the stick. My main problem has been the stick drifting, but like I mentioned yesterday, the stick extended on its own and would not come down until I relieved pressure. Any further ideas or guesses to what would cause that malfunction would be greatly appreciated. Thanks again.
I thought the stick cylinder rod moved out by itself but your saying the stick moved all the way out by itself? That's not a cylinder problem! It's a valve issue and by the description I suspect it's the pilot valve (joystick)
some letters are not working on my keyboard so first off...my apologies. I was working yesterday and all of the sudden the stick/dipper fully extended on its own. Before tat my main problem was the stick drifting down, If I move the pilot control forward just a tad ten the dipper will not rise or fall. If I let it free ten it will usually drop all the way down, ,
I'm still thinking pilot control adjustment or valve body leaking
That sounds like a pilot valve (joystick) problem to me!
Been using the last few days. Recently I was mad at the 420 for not working properly and the dipper dropping so I slammed the throttle up to a max of 20-21 and started yanking the pilot control in all directions. It started working properly and now if it acts up I just repeat my tantrum and it obeys. Any comments as to more throttle and joystick manipulation solves the issue? I appreciate all the help.
I think the problem is in the joy stick, its hanging. Working it like that frees it up for a bit
Yes, it sure seems like it. I've got a guy coming to look at it this week so hopefully we will figure it out. I'll update with the outcome.