Hydraulic Issue on a Bobcat 753C

[Ceilingwalker]

Hello. I have a Bobcat 753C that has just started doing something odd. I am able to use the tilt and lift cylinders a few times, then they start moving only very slightly, then stop. I have to turn the skidder off then back on again for it to work again but then it will only work a few times then start with the minimum movement until I cycle power to the skidder again. I checked hydraulic oil level and it's good. I am using what the dealer recommended, ISO34 hydraulic oil. The skidder will move with no problem in all directions, it's only the tilt and lift cylinders. I searched the internet but have turned up nothing so far. Thank you

 

[Ceilingwalker]

Also, mine has the BOSS but no alarms are indicated or anything. I have foot pedals to control the tilt and lift cylinders, not hand controls. Thanks again.

 

[fortworth-cowboy]

Are you still able to move the pedals when it stops working? Are you able to make a little video?

 

[Ceilingwalker]

Are you still able to move the pedals when it stops working? Are you able to make a little video?

Yes, the pedals still move and the cylinders will make a slight move then stop abruptly. It seems to me that this could be a safety interlock but I can't think of what would do it. I believe this machine might have had a safety bar (or whatever it's called), but the previous owner removed it if it did. Maybe turning it off resets the alarm and then running it the alarm returns? Just guesses on my part.

 

[fortworth-cowboy]

Yes, the pedals still move and the cylinders will make a slight move then stop abruptly. It seems to me that this could be a safety interlock but I can't think of what would do it. I believe this machine might have had a safety bar (or whatever it's called), but the previous owner removed it if it did. Maybe turning it off resets the alarm and then running it the alarm returns? Just guesses on my part.

Wait, they removed the safety bar? Do you see if the seat bar switch is bypassed somewhere?
I am thinking that your Bics valve is going out.
Roll back the cab, make sure to secure it good, then look on your control valve. On the lower part of it, should be a solenoid with 2 wires going to it. Remove that solenoid, if it is baked on that stem it is bad, check if it is cracked or so. I would replace that solenoid plus stem.

 

[Ceilingwalker]

Wait, they removed the safety bar?

Yes, they did. Safety doesn't appear to have been somebody's priority. How they did it, I have no idea. I am sure someone jumpered out that input somewhere.

 

[Ceilingwalker]

I am thinking that your Bics valve is going out.

The cylinders start to make movement then stop, which is why I am not sure this solenoid is bad. It acts like it's doing its job......maybe? It is sensing conditions are not safe and preventing movement but that's just my guess.

 

[fortworth-cowboy]

The cylinders start to make movement then stop, which is why I am not sure this solenoid is bad. It acts like it's doing its job......maybe? It is sensing conditions are not safe and preventing movement but that's just my guess.

What is your serial? And can you take pictures of your RH and LH "Displays" , upper corners inside cab

 

[Ceilingwalker]

Serial number is 512718192. I am not at the machine right now but can take pics later. The left side doesn't have a display. It has a port for plugging something electronic in.......maybe a troubleshooter, a push button for traction control lock and a toggle switch for the lights, and the ignition switch. The right side has that BOSS display, a push button for auxiliaries and another push button but I don't remember what it said. I did notice on this little Bobcat interlocking device that the traction control and a solenoid (both of which have an unlocked sign next to them) are flashing green three times rapidly, then a pause. When the tilt and lift work, the solenoid LED stays lit but the traction control one continues to blink. If I looked in the right spot you told me to, I see two solenoids on a valve block. Are those the BICS solenoid you were talking about? Thank you

 

[Ceilingwalker]

Also, I see a brake relay in the engine compartment. How do engage the brake on this? My machine likes to crawl forward with both arms in the neutral position. I have to bury my attachments in the ground to keep the machine from moving. Thanks

 

[Ceilingwalker]

Other than the two solenoids on the top of that valve block, there isn't another one to be found that's electronic, other than the traction control solenoid, I believe it is. If there is a way to have wired around the control solenoid, I believe the previous owner has probably done it.

 

[fortworth-cowboy]

Other than the two solenoids on the top of that valve block, there isn't another one to be found that's electronic, other than the traction control solenoid, I believe it is. If there is a way to have wired around the control solenoid, I believe the previous owner has probably done it.

Can you take a picture of your control valve? And what you think is the traction control solenoid

 

[Ceilingwalker]

What I thought was my traction control solenoid I believe (now) is my brake solenoid, after looking at the schematics. The other picture shows the control block with the two solenoids. I can't find another solenoid on this block.

 

[fortworth-cowboy]

What I thought was my traction control solenoid I believe (now) is my brake solenoid, after looking at the schematics. The other picture shows the control block with the two solenoids. I can't find another solenoid on this block.

So the 2 Solenoids you marked are your AUX solenoids (Base and Rod side) the other one, how you said, is your brake solenoid but could be also called traction solenoid.

 

[Ceilingwalker]

So the 2 Solenoids you marked are your AUX solenoids (Base and Rod side) the other one, how you said, is your brake solenoid but could be also called traction solenoid.

I can't find this phantom "Solenoid" that the BICS thing is blinking about.

 

[fortworth-cowboy]

I can't find this phantom "Solenoid" that the BICS thing is blinking about.

Can you take a picture of the symbol?

 

[Ceilingwalker]

So, I powered on the skidder and, as the picture shows, all the LED's are steady-on, machine is fat dumb and happy. I don't even have to move it, just run the lift and tilt cylinders for a little bit, then the "Valve" and "Traction" LED's begin to rapidly blink 3-times.

 

[Ceilingwalker]

This is from a book I have however, according to the book I shouldn't be able to move it forward or backward but it moves just fine.

 

[Dave the Ozzie]

This is from a book I have however, according to the book I shouldn't be able to move it forward or backward but it moves

Will the machine creep on a slope if left unattended over a period of time with engine off? If it does than chances are is that the previous owner also had this same issue and physically removed the locking pawl from inside the chain case below the brake solenoid OR the two discs with segment cut-outs that are mounted on each motor are completely shot.
My guess is that if these two lights occasionally flash when they shouldn't then I'd be replacing the whole Hall sensor switch on the left pivot point of the seat safety bar as they can intermittently play up as I've been there, done that.

 

[Ceilingwalker]

Update: My Bobcat dealer showed me that my control valve is on a separate block, which is why I couldn't find the solenoid. After locating the solenoid, I had to hammer and chisel the old one off, clean up the stem with emery cloth, put the new one on, it's now happy! The brake solenoid, I believe, is shot so......once again, my Bobcat dealer told me that if one chooses not to replace that solenoid, they simply remove the wedge that's in there and sure enough. Next trip to my dealer will be to pick up the brake solenoid and that wedge. Thank you everyone for your support.