Desperately seeking help M-312 wheel Excavator!! Does anyone know anything about these machines? CAT dealers just hang up when I inquire about this model. The automatic brake sporatically engages when attempting to travel. It doesn't matter what travel gear, it does it in all. However it is significantly worse and violent in low or "crawl". It will also engage and stop controls when digging or working at low rpm. I need to fix this NOW. I almost killed a man today due to this default. There is no way this has not been an issue. Somebody must know what causes this and how to either fix it or bypass this dangerous feature.
Serial number ?
#6TL01051 Issue is no longer random. It now locks up about every 10 seconds.
Seems pilot cut off pressure switch is playing up Do u lose every control when its playing up ?
Yeah, everything stops, then the brake kicks off and everything is groovy for another ten seconds. This only happens when traveling.
ok, so I found a reference to "low transmission clutch pressure" indicator that produces the exact condition. However no cause or solution was mentioned.
What I know about Cat wheeled excavators could be written on the back of a postage stamp with space left over, however here's what SIS says...... from the O&M Manual (you do have one, right..?) ..... "Low Transmission Clutch Pressure or Parking Brake - This indicator shows that the parking brake is engaged or that there is low transmission clutch pressure. If the transmission clutch pressure is low, the parking brake will engage within ten seconds. If the indicator comes on, the operator should immediately stop the machine. Investigate the cause." or ..... "If the brake system oil pressure drops below normal operating pressure, a warning horn will sound, the parking brake indicator will come on, and the action light will come on. The parking brake will engage automatically." To me that sounds very much like your symptoms and it is a safety system engaging as designed in order to prevent machine damage. Does the Park Brake light come on and the Action alarm sound when your machine stops suddenly..? Attached below is the transmission clutch pressure testing procedure, plus the pilot pressure testing just in case it's not up to spec
Another thought - this machine has two accumulators in the brake system (Ref 18) and one in the transmission system (ref 39). I suggest that it would be well worth checking the accumulator precharge pressure in all three of those as one of the first diagnostic steps.
Nige, Terrific information, thank you. Anything I can find on this unit is helpful. I went out today and started the machine up and just sat and watched the panel without touching anything. Every ten seconds the "P" light would flash and click (I'm assuming solenoids and switches cycling on or off). My problem is that I'm in an accessibly challenged area without access to appropriate test equipment and at least six weeks out for parts if needed. There are no knowledgeable techs near me. I need to figure out how to identify this issue without test equipment.
Then I'm sorry you're fresh out of luck because as a first step you need nitrogen charging equipment to check the accumulator precharge pressures (and to charge if necessary), and as a second step you need 3 x 600psi gauges to hook on to the transmission to check the clutch pressures. Even Superman would struggle in your circumstances. You need test gear.
Nige, Do you have the electrical schematic for this unit?
Yes indeedy ...........
Thank you.
Transmission clutch pressure problems, filters is a good place to start, if you don’t have any testing equipment.
Thank's TVA. Filters are all new. I noticed the problem starts after unit warms up a bit. Seems fine for the first 10 or 15 minutes.