7753 hydraulics locking up on lift only

[shawnjs]

Hey guys, having a bit more issues with my newly purchased bobcat. To date ive replaced the lift lock release valve as it was leaking. Installed a new Safety Bar sensor, old one was only working intermitantly. New Main hydraulic filter, and oil. Replaced various hoses that were leaking or ready for replacement. My issue is the lift will lock up after only a brief time running it. I started by servicing the hydraulic system, and replaced the bar sensor to be sure that wasn't the issue. On my model the overide switch only stops the liift arms from moving up or down, tilt and drive functions work flawlessly. Ive looked in the oil resivoir to see if the oil was foamy to see if cavitation was an issue but everything looked good no air or foam. One of the reasons i replaced the bar sensor was when the lift arms lock up it is exactly as if i haven't pushed the overide button to operate boom, but the light is green so assuming bar sensor is activated. I found a small aluminum block beside lift lock release valve, and it has lines running to it from the lift lock release valve almost looks like a loop. Theres also a solenoid type valve on the side with a 2 wire electrical connection on it. Does anyone know if that is the solenoid for the overide switch? If so how can it be tested? Or if anyone has had a similar problem I could use some help. Model is 7753 manufactured in 1993. Has the basic mechanical guages in it, no seat sensor. Thanks Shawn.

 

[Bobcatdan]

I think a 7753 would have these newer machines do. Look on the front of your control vavle where the likage connects, there should be two solenoids, one for lift and one for tilt. These are spool lock solenoids and I would guess there is problem with the one for lift. Lift is the lower one The solenoid could be the problem, but the fact it works then don't, it may be power supply. There should be a BICS box with four LEDs behind your right arm, what is the LED for lift doing? If it is blinking, count the lights and let us know, thats a problem code.

 

[7LBSSMALLIE]

I think a 7753 would have these newer machines do. Look on the front of your control vavle where the likage connects, there should be two solenoids, one for lift and one for tilt. These are spool lock solenoids and I would guess there is problem with the one for lift. Lift is the lower one The solenoid could be the problem, but the fact it works then don't, it may be power supply. There should be a BICS box with four LEDs behind your right arm, what is the LED for lift doing? If it is blinking, count the lights and let us know, thats a problem code.

very good description ,makes me want to help.early 7753 had a seprate lift block located (on right side ) folow lift ines .above main frame .6 inches down and behind fan shroud this was reffered to as lift lock valve.this was prior to rest of saftey stuff, therein lies youre issue. and dont even think of bypass ive seen death by bobcat up close and personal, this exact same model , stem or solenoid either or, solenoid when on should have a magentic field. stem remove and check for freedom of movement, dont screw this up youre life or others depend on it>>> simple block doesnt go bad stem or solenoid. get both avail as a kit:::::O NOT DIE FOR A HUNDRED BUCKS<< I FEEL GUILTY AS IT IS

 

[7LBSSMALLIE]

very good description ,makes me want to help.early 7753 had a seprate lift block located (on right side ) folow lift ines .above main frame .6 inches down and behind fan shroud this was reffered to as lift lock valve.this was prior to rest of saftey stuff, therein lies youre issue. and dont even think of bypass ive seen death by bobcat up close and personal, this exact same model , stem or solenoid either or, solenoid when on should have a magentic field. stem remove and check for freedom of movement, dont screw this up youre life or others depend on it>>> simple block doesnt go bad stem or solenoid. get both avail as a kit:::::O NOT DIE FOR A HUNDRED BUCKS<< I FEEL GUILTY AS IT IS

SHARING THIS INFO IN THE WRONG HANDS ALBEIT 20 YRS OLD. CAN LEAD TO MISTAKES, USSAUALY WITH BAD RESULTS. ITS NOT A SECRET JUST NEEDS TO BE HANDLED RESPONSIBBLY.

 

[7LBSSMALLIE]

SHARING THIS INFO IN THE WRONG HANDS ALBEIT 20 YRS OLD. CAN LEAD TO MISTAKES, USSAUALY WITH BAD RESULTS. ITS NOT A SECRET JUST NEEDS TO BE HANDLED RESPONSIBBLY.

DONT MEAN TO HOUND. BUT LOOK AT HYD SCHEM AND ELECT SCHEM TO SEE HOW IT INTERACRS FOR LIFT LOCK VALVE.

 

[biggie]

DONT MEAN TO HOUND. BUT LOOK AT HYD SCHEM AND ELECT SCHEM TO SEE HOW IT INTERACRS FOR LIFT LOCK VALVE.

7LBS. Help me out. Seen a 751, with a small block back of the brake soleniod, with a soleniod and a couple of hyd lines going to it. Is that a lift lock ?

 

[shawnjs]

7LBS. Help me out. Seen a 751, with a small block back of the brake soleniod, with a soleniod and a couple of hyd lines going to it. Is that a lift lock ?

Thanks again for the help guys, this forum has lots of great info. It turns out it was a bad solenoid and valve for the lift only. It was only getting intermitent voltage because i had a bad safety bar sensor that was only supplying it 5-7 volts, not the 12 required. As soon as I replaced the Safety bar sensor it was supplying the required 12 volts and fried the solenoid melting it to the valve itself. Im guessing here but assuming the low voltage being supplied by the bad bar sensor caused the solenoid to work twice as hard and wore it out prematurly. Installed a new solenoid and valve and it works like a champ now. Thanks again, Shawn.