Hi all, I have a 773G model with AHC (advanced hand controls), no foot controls. It’s got the BICS system on it. No seat switch. I was out plowing snow the other day and when I finished I brought the 773 in my shop and let it thaw overnight. Next day I find a decent sized puddle of hydraulic fluid under it. I tracked it down and found it was leaking from the Oring where the solenoid valve threads into the BICS valve. I was relieved and thought great an easy fix. (Yeah right) Replaced the Oring (old one was shot and had pieces coming off it), checked for leaks, all good. I did not have new Orings and back-up rings for the stem of the solenoid valve itself but they looked good and it had been working flawlessly. I fired it up to move it out and couldn’t lift the boom or tilt the bucket. When I try to lift or lower the boom it does load the engine but will not move the boom. When I tilt the bucket down it loads the engine and it will tilt down just a hair and take some weight off the front tires but won’t pick them up. When I tilt the bucket up it loads the engine but won’t tilt the bucket up. I do hear a hissing noise like hydraulic fluid flowing internally in the valve. Kinda the same sound of hydraulic fluid flowing thru a relief valve or flowing by a partially opened valve. Here’s what I have done so far: * checked and have all 4 green LED’s lit up on the BICS controller in the cab * when I had the solenoid valve out the second time I applied 12v to the coil and the valve appeared to be moving as it should…clicking in and out. * checked the wiring harness and had 14v to the connection where the solenoid valve plugs in. * fired it up, hit the operate button, had all 4 green BICS LED’s lit up and stuck a screwdriver down by the solenoid coil. Had some magnetic field but it felt pretty weak. Not sure how strong that should feel with a screwdriver??? I didn’t get to it yet but gonna check the resistance to the solenoid coil and make sure that’s within specs. Has anybody had an experience like this, or these symptoms? Any ideas would be greatly appreciated. Hydraulics are not my strong point. Thanks, Bruce
Update: I checked the resistance on the solenoid coil. It was 10 ohms. Specs say 8.7-10.7 I’m kinda at a loss. I guess I’ll pull the relief and make sure it doesn’t have some crud in it. When I said in the original post that the “old Oring was shot and had pieces coming of of it”, I should have said it was intact but had some erosion and areas with nicks out of it that obviously let oil leak by externally. Who knows maybe somehow a tiny piece of that ended up getting in the valve and hanging something up. Thanks again, Bruce
Sure sounds like a bics issue if tries and then loads over relief. I think your on the right track. . .
Not sure if it would apply but could aux. hydraulics be engaged?
They are not. I did engage the aux. Hyds. and shut it off, made no difference. Still not working. I have an update coming later tonight of the things I have done and what I was thinking of doing next.
The coil being energized and pulling does not mean it is moving the spool any. And yes any small piece of dirt could be hanging it up. Simon C
Update: * I welded up some fittings and hooked up to the auxiliary hydraulics and checked the hydraulic pressure. idle=2500 psi. About 1/2 throttle=2800 psi and I didn’t go any higher as the machine was in my shop and not warmed up. 3000 psi is the spec. I engaged the auxiliaries and ran them in each direction and had the same pressures in both directions. That tells me the pump is working, the main relief is not stuck open, oil is making its way through the main control valve, and the auxiliary spool is moving correctly. * I pulled the solenoid valve out again. Grabbed my air nozzle with a rubber tip and blew air through the end of the valve stem and it was coming out one port on the valve. I energized the coil and it came out the other port on the valve stem. I could visually see the plunger was moving and the air confirmed it was moving from port to port. As I said in an earlier post the Orings and back up rings on the valve stem are not damaged and look fine. Also looked into the bore where the solenoid valve threads in on the BICS valve and it looks good/clean. * I pulled the pilot actuated locking valves out of the BICS valve. The solenoid directs oil to these valves to open them when you push the ”push to operate” button on the panel. They have to open to allow oil flow from the tilt or lift spools to the cylinders. They were both clean and free of any kind of debris. They moved freely while pushing them with a screwdriver to open and close. The bores both looked clean and free of any kind of debris. * I turned the key to the on position, hit the push to operate button, had a green light for the lift and tilt on the BICS panel. I moved the lift and tilt controls and I can hear the actuators moving in both directions. Obviously I can’t actually see that the spools are actually moving but can hear that the actuators are working. If I fire up the bobcat and tilt the bucket down it will tilt down a bit and take the weight off the front tires. If I then shut the machine down, turn the key back to the on position without starting it and hit the push to operate button, then tilt the bucket to the up position I can hear the actuator work and the machine settles back down as the bucket tilts up. This tells me the actuator is moving The tilt spool at least a little bit. Today I’m going find a place to tap in and get some hydraulic pressures after the control valve/BICS valve and before the tilt and lift cylinders just to rule the cylinders out. My machine is fairly basic and doesn’t have a Bob-tach, bucket position valve, or diverter valve for rear auxiliaries. So that eliminates places for internal leakage. Basically I have hard lines or hoses right from the main control valve/BICS valve to the cylinders. Am I missing something here? Seems like a fairly simple system, but hydraulics are not my strong suit. The machine was operating flawlessly before I pulled the solenoid valve out of the BICS valve and replaced the oring.
Here is the legend
If you could hook up gauges after the control valve with the line dead ended, you would see maximum pressure, leakage, whether or not the opposite side of a spool is pressuring up at the same time. Not sure how hard to get at, but have taken a hydraulic plug before and put just a tiny hole through it and tapped the back end for 1/8 npt thread for a gauge setup. More testing may reveal something. Simon C
That’s pretty much what I did.
Another Update: I tapped in and checked hydraulic pressures after the control valve and BICS valve and before both the lift and tilt cylinders. pressures were checked with the lines going to the cylinders dead headed. Heres the results at idle: Tilt up ——— 0 psi Tilt down ——2500 psi Boom up ——0 psi Boom down - 2500 psi Looking at the hyd. schematic both Tilt up and Boom up oil flow goes thru the control valve, then thru the pilot activated lock valves in the BICS valve, and then onto the cylinders. I’m assuming the lock valves are not opening therefore the 0 psi readings. The Tilt down and Boom down oil flow goes thru the control valve, then to the cylinders, then the return oil from the cylinders goes thru the pilot actuated lock valves in the BICS valve. This side I am getting 2500 psi but assuming the lock valves are not opening I am not getting flow and the cylinders are not moving. So to me this just points back to the solenoid, the only thing I messed with before I had the problem. Just to make sure the control valve tilt and lift spools were moving as they should, in both directions, I took the end caps off the valve body on the opposite side of the actuators. I measured the spool travel in both directions and they were all the same. Am I thinking straight here? Anybody have any other ideas? I ordered some seal kits for the lock valves, a seal kit for the check valve with the screen, Orings, and a solenoid. I’m headed down to America to see my folks and help out around their place. Hope to get back after this the end of the month or early Feb. I’ll let you fellas know what happens.
Well you have verified some pressure, and where you have none. Some solenoids work differently under pressure, in other words they don't work. Items 16 & 17 are suspect if they do not switch. Is it possible to check for pressure on these when they are commanded to shift. Spool #20 is what feeds the rod end of cylinder when actuated to curl bucket back up. Beside it on the Schematic is the Letter C. Could a gauge be installed there. Have to look at schematic more. Simon C
I was wrong. Spool #20 is an unloading spool. #17 is part of your bics and is how the oil goes to the rod end of Cylinder for tilting. Need to check the 2 screens #33 which feeds 16 Solenoid. If not enough oil from choked off filters, no bucket curl up valve #17. That is possibly what is wrong and at least needs to be ruled out and is part of the necessary maintenance. I believe it is some kind of bronze sintered filter. Probably need new ones. Simon C
I'm kind of glad I didn't buy a skid steer with any electronics or solenoid valves. I've heard the early BICS were problematic.
Thanks Simon. I think you may be right, I am at the point where I figured even though the solenoid seems to work when testing it out of the machine it must not be working under pressure. I pulled both pilot controlled locking valves out (items 16&17) they were clean, moved freely and easy when I pushed on them with a screw driver, and the seals looked good. I ordered seal kits for these two valves as well. These valves are in the BICS valve which is bolted onto the main control valve with internal passages and there is no way to test pressure going to open these valves. I do not have the bucket position valve on my machine. (Where spool 20 is located) Just hard lines and hoses from the BICS valve to the cylinders. Which is where I tapped in to check the pressures. I ordered a seal kit for the check valve/screen (item 33) and plan to check that when I get back. It is a pain in the butt to get to as I would have to take a bunch of stuff apart to get to it. It is upstream of the solenoid so figured the chances of it getting debris in it from me changing the oring on the solenoid was very low to impossible. I believe the second screen past the check valve (item 33) is actually on the solenoid. But not positive on that. The solenoid has a stainless screen on it, for the incoming oil I assume. It’s 35 below today (freaking nippy), I am running out of time to work on this. I have other things that need to be done before I head to see the parents. I chained up the bucket, pulled it out of the shop, and parked it. I appreciate the help and suggestions. Sounds like we are both thinking along the same lines. I’ll get after it when I get back and get this figured out one way or another.
I’ve only put about 150 hrs on the machine since I bought it. It has just over 1600 hrs on it. So far it hasn’t given me any problems until this issue. Hope this is not a glimpse of what is to come.
Yes there has to be sufficient oil getting past #33 Screens. There either is or is not. Had another look at schematic and I am thinking there is where the problem is. Have done the Case Drain sintered filter on a T190 Bobcat and had to remove a lot of pipes and hoses to be able to do it. Some people have said don't bother and the traction motor exploded on them. Maintenance is hard in cold but not to bad with frost fighter. Your schematic is very helpful, as just throwing parts at otherwise. When you get back to it let me know what you find. Simon C
Well I’m back from America and gott‘er fixed. I had the parts shipped to my parents place in Oregon for free. They wanted $200 for UPS ground shipping to AK. We get screwed up here on shipping quite often unless the company will ship USPS. Anyway… When I got back I took the check valve with the screen out (#33) it was good to go. Clean, check valve moved freely, and seals were good. I put the new solenoid valve stem and a new coil on the machine and that fixed the problem. Praise the good Lord Almighty and thank you Jesus. I was stoked and was getting tired of playing a contortionist and working on that thing. Lol The valve stem and coil were sold separately and with $200 for shipping I wasn’t gonna take a chance of trying just the valve to find out it was the coil, or vice versa. So I bought both and installed both. The shipping was about the same price as the valve stem and coil. Anyway it’s done. Thanks for all the help. You guys are awesome. Much Appreciated, Bruce