I went out to a job on a 345 excavator, complaint is boom dropping. When operating the machine, boom will lift ok then sometimes as it is being lifted it will drop to the ground very fast while control is still in lift position. When using the controls very slow it it worked for a short while, boom did not drop. As soon as I tried normal speed boom would drop. After I released the pressure in the hyd. tank and checked the oil level (no oil added) every thing worked ok for rest of the day. the problem is intermittant some days ok. Any help would be good
Air in the system somewhere?
Does it have Boom lowering control valves on the boom cylinders? Smartboom? I'd suggest putting a gauge on the boom down pilot line in order to see if it a pilot system fault or not.
There are no boom lowering valves on the cylinders. When I get back to the machine in a couple of days I'll put some gauges on the pilot lines and see what is happening. Thanks I'll let you know the results.
You can switch places on the boom up line relief valve and some other, they are all the same. Maybe pull the boom1 and boom2 stems and check that they look good.
Thanks I'll give that a try as well, when I go back to the machine.
Yeah I dare say the it would be the relief valve. Our 330Bl was recently doing the same thing so I swapped the lift relief and the lower relief. Shane
The customer won't let me stop the 345 for testing at the moment, to busy. However, with the 330BL was the problem there all the time or just first start up from cold, which it seems to be with this one.
345B's were known for having boom & stick dropping problems with cold oil due to faulty line relief valves. I would try replacing the boom head end relief valve. It is on the top of the boom 1 control valve right next to the drift reduction valve.
At last i've got the machine to work on. Due to excessive leaks around the control valve, we removed the entire valve, and have just stripped it down, first thing we found was a damaged swing priority valve, and missing seals on the regeneration valve. A lot of the seals are hard through heat. Tomorrow we will inspect all the relief and check valves. Thanks I will keep you up to date.
The regen valve are known to cause all sorts of problems, I should have mentioned that before really.
I have two 345bl doing the same, one regen valve was missing all of the o rings, machine had no fine control in any joystick so replaced them on advice from cat dealer. Worked ok for a day now no fine control in boom, thoughts?
Hard to control the boom both up and down?
Yes, there is no fine control in the boom at all. Boom is very jerky and the circuit is only actuated at the very end of the control handle straight up or straight down. Thanks.
Check if the boom spool moves smoothly in the valvebody first. Then put a gauge on the pilotline from the joystick to the controlvalve and check if the pressure follows the joystick movement.
Update on 345. Problem was found be a valve in the main control bank, which had stripped the threads. allowing the valve to stick in one position, this was only found when we stripped the entire valve down. part number of the valve is 122-7690, it comes as a complete assembly. thanks for all help.
Main control valve was removed and overhauled, drift valve barrel was stuck in main control valve body and a spool had a loose bolt. Apart from this the valve was ok. Fitted valve back onto machine and operated, problem still present, that is that there is no fine control in boom up or down. Will measure pilot pressure in pilot valve when mode is operated tomorrow.
Sounds like boom 1 spool isnt moving. Does this machine have an aux circuit that has the pilot lines tied into the boom pilot lines with a shuttle? If so cap off those line and see if it changes. Gauges on the boom pilot lines will show you if the pilot side is working smooth and the main pressures will show how the pumps are responding.
Put pressure gauge on pilot line for boom 1 and boom 2 at MCV and recorded no pressure when joystick was moved until joystick was almost at the end of its travel then boom jerked up and gauge read about 300 psi on both tests. Put gauge on stick 1 and gauge recorded all movement of the joystick so gauge is good. Tomorrow I plan to swap pilot lines at MCV with another function to see if problem moves or is eliminated. Thanks.
If this machine has the pattern changer, flip it to see if the problem swap or stays with the joy stick. B models were just starting to come with the changer so it may not have one.
Switched bucket curl lines with boom lines and problem moved to bucket. Boom/bucket control valve is brand new from CAT so going back under warranty. Thanks for the help everyone. Have another problem AGS01473 serial#, that two local dealers can't find the problem with so may seek your help again.
Well that didn't last long. Boom up and down became jerky again. Plungers for boom up and down are about 1/4 inch lower than the plate in the control handle. With machine running and control handles in neutral, when you engage hydraulics boom goes up and continues to labor pump with cylinders fully extended. Any idea's?
Sounds like crap gets into the pilot valve, did you pull the old one apart and take a look for metals havings and such? might be some left in the lines going back and forth?