I have never been so aggravated as I have been today! I am much more an operator than I ever was a mechanic, but I am mechanically inclined, semi-retired to fooling around with my own projects and machines and WANT to be of some use to myself these days, so I decided to take on this *!@@!!*#@ of a machine on my own. Hopefully with a little help from some fellows I would like to call friends! Well, to start, I watched a steady ****** of hydraulic fluid shoot from the backside of my tilt spool. Easy enough, ran down to the local dealer, grabbed a set of seals, replaced the spool seals and put her back in......two minutes later I watched a steady ****** of hydraulic oil run out the back of the lift spool. Lol. Well, I kind of expected that, but hoped for the best. I have read enough of these threads written by very competent mechanics warning against doing a half-assed job, but I thought I knew better......and there it is . So I started moving lines, pulled the control valve off the wall, threw it on my work bench, went back to Bobcat and got a complete control valve seal kit and went to work. Couple days later I slapped her back in, hooked the lines back on, and then began filling up the reservoir. Cracked a line at the gear pump and saw oil flowing....checked the reservoir and noticed that the oil level hadn't dropped much from where I had filled it, although I caught over 10 gallons of fluid. Tried to raise the arms to get the lift safety bar out and drop the arms back to the ground.....and nothing. Tried to tilt the bucket back up as it had seeped off....nothing again. Jacked the arms up, drove 4x4 posts under them to support them, knocked the safety bar out from the lift cylinder, drove forward to get the 4 bys out from under the arms and then tried to lower the arms.....and nothing!! I had to climb into the engine compartment with the cab up and crack the main hydraulic line open and pull up on the lift arm relief valve in order to get the arms down!! I am positive that this is something that I did wrong on my own, but I cannot for the LIFE of me figure out what the heck it could be. Anyone ever deal with this before, or heard of someone that has dealt with this before? I am very thankful to have the arms down and the bucket back on the ground, but I am at a total loss as to how to correct this issue...any help would be greatly appreciated.:Banghead
I'm not familiar at all with the 751, but just a thought, is it possible you have the auxiliary hydraulic circuit engaged?
I'm not familiar at all with the 751, but just a thought, is it possible you have the auxiliary hydraulic circuit engaged? Willie, this machine has aux button on the right upper side of the cab, I did jump in it and try to slide the handle to the left like some do to engage aux, but it definitely isn't a manual engage.
You stated you had the main control valve on the bench to replace the seals. If it were a manual engage aux hydraulic valve you would have notice 3 control spools controlled by linkage, 1 for aux, 1 for lift, and 1 for tilt. All other Bobcat control valves are controlled by two solenoids which are controlled by the thumb switch on the right joystick. Again, I'm not familiar at all with the 751, so my comments reflect that. Is this a C, F, or G series machine?
Correct, I had it on the bench and it had two control spools and I STILL had to make sure it wouldn't manually engage. Silly, I know, but I did it. Its an F? (BICS behind the seat). 514711786 #. Willie, here is the mysterious part for me that I can't stretch my brain around: why would none of the lfuid I put into the reservoir be pulled into the system? What would not be opening to allow flow? Do I need to bleed anything?
BTW, reading your advice on the control valve reseal on the 773G, Willie......Man! Wish I had spotted that before I started on this one, your way of doing it seems a hella lot easier than wrestling it like I did the 751
F Series, yes, auxiliary hydraulics would/should be controlled by thumb switch on right joystick. Given this, I don't think that's your problem, rather, it sounds like a fault with the BICS lockout valve on the main hydraulic valve. Very important, when you start the machine and drop the lap bar, are all the LED lights on the BICS controller lit up? As for the fluid, Bobcat machines don't use a return to tank system, rather, it's an enclosed loop system, all the reservoir does is keep the loop filled. If all you did was disconnect the main control valve, then re-install it, it shouldn't have affected the suction side of the gear pump which delivers oil to the main control valve and provides charge to the drive pumps. In short, if you can still drive the machine with no issues, you don't need to bleed anything, the enclosed loop is working. Given the information disclosed thus far, I wager you have a problem with the BICS lockout system
Ok, that's a good place to start. But you open a new can of worms Willie. When I got this machine, I noticed someone had jumped the BCIS solenoid (located under the reservoir on the operator's right side) from the brake release. Tonight I took off the jumper wire on the solenoid side, turned the key, hit the switch for the brake release than then touched the wire to the green solenoid wire and could hear the solenoid engage faintly. They had it taped, I went ahead and put connectors on it to clean it up a bit, but I am going to double check my work on that in the AM. The seat light blinks twice and the lift arm/bucket light doesn't light at all. The lift and the tilt worked fine before I took on this project with this jumper wire....so...... What about fuses or relays? Would any of those come in to play? I'll check in tomorrow night with my progress (?) Thanks for giving me a hand Also, lap bar and traction lights are steady lit, seat double blink and arms bucket no light.
Well there's your problem. In order for that machine to work proper (former spaghetti wiring shade tree mechanics notwithstanding), all the lights on the BICS controller must be lit. An LED light that is blinking is a trouble code, although very basic in giving any real information to work with, the jump to the G series BICS was a quantum leap in on board diagnostics. As for the BICS solenoid, it would be a solenoid valve mounted on the main control valve itself. If I recall correctly, on a F series, aside from the two solenoid coils on the main valve that control the aux hydraulic circuit, the BICS solenoid would be the only other electrical coil on the main control valve, I don't think the F series had spool lock solenoids. I don't know about the previous wrench benders jumper wires and rats nest electrical tape wiring remedies, but as for the BICS coil on the main control valve, yes, it's just a 12V coil, you could simply connect 12V positive to one wire and a ground connection to the other wire and it would power up the coil. This would allow you to at least work the machine to verify your repairs, but if it does now work proper, I strongly suggest you get the BICS system sorted out and working proper, it's much better when a machine works the way it was designed to do so.
sounds like you still have an old style bics controller that has the seat safety switch. my advice is to purchase a seat bypass bics kit from your local dealer, and install it. make sure after you install the updated kit, that you disconnect the seat switch from the system. :drinkup
Bottoms up CrewChief! I will take that advice and call the dealer tomorrow. In the meantime I am going to try to get that jump to work again to see how I did on my reseal project....aggravating sunuva......Of course the wifey caught me pulling on the shop clothes this morning and shut me down and drug me out to go Christmas shopping this morning....shoulda seen the look of death I got when I suggested I wouldn't get dirty but needed to go out there and try to figure out a couple things before we left......needless to say.....no shop time for this old dog today. I'll get after it tomorrow and get it figured out then start replacing cobbled up electrical masterpieces.
I forgot about that pesky seat switch. I'm glad Bobcat quit using those things.
I got the BICS valve to open and got some action out of the lift arms, so far no leaks. Bad news is that the lift arms were working off the right pedal (the tilt pedal) and were working very intermittently. I have no tilt at all, and on several occasions the lift was jerky. On one or two tries, I actually had to press down on the left pedal about half engaged and press up on the right pedal about half engaged again to get the arms to raise. What was scary is when I would relieve pressure to lower the arms, they would drop like a 10 ton stone. Any thoughts on this? I am in this deep, and as far as I am concerned I am further today than I was Wednesday...so I am gonna keep trying to get this right. :idontgetit :idontgetit:idontgetit
I feel like I have run everyone off that was offering advice....and I think i know why......I sound like a complete dummy. Maybe I am, but I can read and understand basic English, so don't give up on me . I went out there this morning to make some more observations to give myself a better place to start researching the world wide web. The right pedal is definitely the one that is raising and lowering the arms. But only intermittently. The left pedal will make the cylinders jump just a wee bit, but no lift. Most of the time I had to engage both pedals about halfway in order to get the lift started up, but then could let off the left pedal and use the right one to lift all the way. Each time I took it up, the low hydr light would intermittently flash, but in checking the reservoir she is at the same lever as when I filled it. When I was using the right and left pedal, more than once it seemed like the load was going to kill the engine. Lastly, I raised the arms to full height, pull the manual lift bypass and nothing happened, no release whatsoever. But like I said above, if I depress the foot pedal to lower the arms, it drops like a ten ton stone.....although I did discover that if I focus on light pressure on the pedal, it does go down like it should, smooth and slowly....something must have increased the sensitivity to that. So my main question is......why would the controls be reversed? I checked every connection, even paying attention to how the tubes were bent around other lines to make sure I didn't cross anything up. It all looks good. What would keep the manual bypass from functioning properly? Is it an indication that the lock out solenoid is not working properly? It is on a block by itself just as the lock out solenoid is. I have with the motor off jumped the lock out valve (on my machine it is located just behind the control valve, under the reservoir and next to the fuel tank hose), and I can hear it opening and shutting as I jump it. I have read a few posts about the aux spool having some sort of interference, but I haven't quite come to terms with that seeing that I just replaced every seal there was on the main control valve. On my bench, after a thorough cleaning and with bright work lights and my glasses on.....I am confident I did it correctly. Only one thing really wigs me out......is there ANYWAY I could have put the spools in backwards, I mean, would the control valve allow that? I guess there is one simple way to find out, and that is to walk my ass back out there and pop the back cap off the tilt spool.....if bbs start flying I know what I did wrong.
Well no, you haven't "run us off", rather, you've got us stumped with what you're describing, but the problem for us is there's now too many things that we don't know and have no way of knowing, such as, were all connections put back in there proper place when you re-installed the valve? Did you swap the two control spools? And there's still the possibility that you have an auxiliary valve stuck open. I have no idea how, just saying it's another thing I can't know for sure.
I understand what you are saying, and I appreciate you responding with that because I really thought I had you guys rolling your eyes and walking away. I can tell you that according to the photos in my service manual I have all connections correct. I didn't check the spools today like I said I was going to because it seemed like there was no chance of that happening, the caps are different lengths for obvious reasons....and the end caps are in the correct locations. Let me ask you this Willie, when you did your tutorial on the 773 spool seals, one of the things you pointed out was to keep track of which hole the clevis pin came out of on the lift spool. IF you were to put it back to the wrong hole what effect would that have on "things". I have read and re-read my service manual, and have gone out to the machine and stuck my head in the belly about 100 times today.....nothing any different than it was at the start of the day. I guess the next step is to roll it over to Bobcat and admit that I am over my head, but it seems like there is something I am overlooking that is going to be an Ah ha! moment when I figure it out. I may just pull everything back to where it was before I had to come out of the shop and to the computer and go at it again.....I hate giving up just because it gets tough. I should be able to bench test the aux valve, the tilt lock valve and the lift by-pass shouldn't I? If I take it back down to the basics, I think I will take photos and do a step-by-step this time.....maybe I can help the next hack that is over his head with some trial by error details. Next on the list is an S250 chaincase swap, which I am looking forward to, the arms can set to the side while I work on that one.......if I can get this one to work well enough to get the arms off and set to the side that is!:beatsme
Also, someone somewhere mentioned a bucket float valve located in the back of the engine compartment on a different machine experiencing similar problems...on the s250 that is a switch on the control panel, but nothing like that on this old beast. If such a float existed on an early model 751, where would it be located?
I've never worked on a 751 myself.
If I'm not mistaken the two coils that control the auxiliary circuit are not 12V coils, they work off of a PWM signal from the main controller. I'm thinking if you put 12 volt on those coils they'll loose their smoke.
Ok. I think my plan of action is to use the machine as it is.....it drives perfectly. Get the cab, arms and body off the s250 so I can start painting it, and then work this thing backwards to where it was when I pulled the tilt spool the first time. Maybe Bobcat can test those coils for me, I will call them Monday. I can (and probably should have) pull the tilt lock valve and coil and the lift by pass valve and the check valve and replace their seals. I'll take photos and try to help the next guy out. Thanks for all of your advice on this post and all the other posts Willie, you have no idea how much you help guys like me out