Hi all, New here I have been reading around for a long while and we finally have some down time to work on equipment so was hoping perhaps someone could help me narrow this down. the Machine is a Bobcat 1999, 873, high flow 2 speed. I have rebuilt every hydraulic cylinder in the past year. Since I have owned the machine there has always been a slight droop of the boom, although rebuilding the lift cylinders helped it still is present although now only with a load in the bucket. this past fall I noticed the lift power on the machine decreasing. It started I was unable to pick up 4000lb pallets of sacrete. (which it would pick previously) I can get it to kinda work its way up by either curling or even just rocking the machine forward and backwards seems to help inch the arms up? The low power on the lift has been getting worse over time. Curl could still move the pallets around fine. for part two which may or may not be related. My Aux hydraulics/grapple seems to be having issues.the grapple will not lock shut when I grab a heavy rock or log. After I released my thumb from the switch it will ease back a hair which makes holding things tight difficult. So in order to hold something tight I have to keep my thumb holding the aux hydraulics on, which impedes the curl functions performance. Then the other day I got in pressed the aux hydraulic button on the upper control panel and the aux hydraulics were activating with no input from the thumb switch. The grapple would just slam close, I could get it to open by pushing the switch the other way, but as soon as I released the aux switch they would slam shut again and you could hear the pump working continuing to try and close further. Ideas? Switch? solenoid on valve body? I should also note that the 2 speed travel switch appears to not work which is in the same control as the aux hydraulics. I also have noticed that I can hear the sound of hydraulic fluid flowing through a valve or something (like a function is being used) coming from under the seat (valve body I assume) even when I am using no function just sitting there letting it warm up. Any Ideas? Oil is clean, Filters changed. Thanks in advance Lucas
Bobcat 873 Several hydraulics issues, Weak lift, uncontrollable Aux Hydraulics
- Thread starter GMMS
- Start date
Help Support SkidSteer Forum:
walio123
Well-known member
- Joined
- Dec 9, 2013
- Messages
- 367
As far as I understand your machine is 873 instead of 783. It look like main hydraulic reliev valve problem or weak gear pump. You can check Aux hydraulic solenoids wiht .Unplug the solenoid connectors, pull the trigger, have 12 volts, you can measure the resistance of the two - it should be the same / I can check how much it is /. To check reliev valves and gear pump you wiil need a pressure gauge and flow meter.If you dont have my advice is to turn to a specialist. If you have 250 bar pressure gauge i will tell you how to check it.
I do have a pressure gauge. Where is the proper spot to test from on here? thanks Lucas
walio123
Well-known member
- Joined
- Dec 9, 2013
- Messages
- 367
If you are familiar with how the hydraulics work is ok. You can tie the pressure gauge to one of the auxiliary hydraulics ports and trigger it. The relief valve will work and you will see what pressure you have. However, this will not give you an answer if the relief valve is not working corectly or pump is bad. To understand without a test bench whether the gear pump is ok, you have to disconnect the pump's high pressure hose and roll a pressure gauge. Disconnect the shut off solenoid cable to prevent the engine from starting and turning on the starter for not more than 1 sec. / 3-4 revolutions of the engine / pressure gauge should be at least 250 bar. Be careful, because if you turn too much you can damage the pressure gauge or worse, break the pump housing. However, I recommend that you turn to a dealer who has a suitable tester for it. It is equipped with a relief valve, throttle, pressure gauge and flowmeter and will not damage anything.
I fixed yout typo.
You mention your aux hydraulics are a bit weird, i wonder if that could be causing issues with your lifting power too. Stems can get a little sticky, so they won't always shut off till pressure builds and they release, i wonder if that could be some of the issue.
A pressure test on you rhydraulic system is a good idea, it should be close to 3,000 PSI, it is generally measured at the quick couplers, as it's easy to access and it's past your relief valve to keep your system safe. Never plumb direct into the pump as if you dead head it, something will let go.
