Bill Murrell
Member
Had to remove drive axles to move it. Tow valve would not release the park brake
-
Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!
D3C LGP Hydrastat
- Thread starter Bill Murrell
- Start date
-
- Tags
- cat cat d3c cat hydrastat
Nige
Senior Member
Best way would be to troubleshooting the wiring using the electrical schematic. If you don't have one then send me a PM with your email address - you can have a pdf copy.
Bill Murrell
Member
Trouble shot the electrical and found the interlock switch on the joy stick inoperative. Once we bypassed the switch with the tractor running the parking brake like goes off and we felt the hydraulic solenoid next to the towing valve actuate. Could I be so lucky?
Have a new switch on order and will let you know what happens. Please send me the info for checking the pressures on the brake hydraulics if possible.
Thanks for all your help and have a great weekend.
Have a new switch on order and will let you know what happens. Please send me the info for checking the pressures on the brake hydraulics if possible.
Thanks for all your help and have a great weekend.
Bill Murrell
Member
Replaced the safety interlock switch on the master clutch lever and the brake light went out for a few minutes. Now the brake light is bright until the interlock switch is activated then dims some. Checked the brake pressure at the tow valve and it was somewhere around 350 to 400 lbs (not a very good guage). Any ideas?
Nige
Senior Member
According to the Service Manual the parking brake is "likely to release" at anything above 30psi. Have you got your Service Manual yet..?
Are you sure about that 350-400psi value..?
The reason I say this is that brake pressure switch deacuates at 51psi, so that should put the light off. The low brake pressue indicator light gets power from the key switch. the idea is that when the low brake pressure switch opens it cuts the connection to ground and the light goes off. Are you SURE you don't have a wiring problem first of all..? Have you tested the low brake pressure switch using a DMM to see if it opens immediately when you hit the brake release switch..?
Are you sure about that 350-400psi value..?
The reason I say this is that brake pressure switch deacuates at 51psi, so that should put the light off. The low brake pressue indicator light gets power from the key switch. the idea is that when the low brake pressure switch opens it cuts the connection to ground and the light goes off. Are you SURE you don't have a wiring problem first of all..? Have you tested the low brake pressure switch using a DMM to see if it opens immediately when you hit the brake release switch..?
Last edited:
Bill Murrell
Member
I will get another gauge on Monday to verify the pressure. I am not confident in the accuracy of the gauge I have. The shop manual is a help but leaves a lot to be desired. Where is the brake low pressure sensor located? I can't find it.
Bill Murrell
Member
Forgot to mention that I am testing the pressure at the test point at the tow valve with the tow valve closed (in the normal position).
Nige
Senior Member
It's not a sensor, it's a switch - nothing more complicated than open/ckosed. See attachment - Item 9, it looks as though it's on the line to the RH brake pack.
rondig
Senior Member
Nige....why dont you move closer to us...damn your good at what you do....do you know anything about anything else than CAT yellow?
Bill Murrell
Member
Nige
Torn the machine down and found the brake discs were fried. Had to get the new ones from out of the county. Got everything back together except for installing the brake pedal switch. Part of it was found missing. What should the actuating pressure be for the brakes? Mine shows around 430 psi when brakes are applied. Thanks in advance for your help.
Torn the machine down and found the brake discs were fried. Had to get the new ones from out of the county. Got everything back together except for installing the brake pedal switch. Part of it was found missing. What should the actuating pressure be for the brakes? Mine shows around 430 psi when brakes are applied. Thanks in advance for your help.
Nige
Senior Member
Spec is 420+/-20psi. Here is the complete Test & Adjust for the Hystat Power Train. You need to look on Page 48 for the brake test procedures.
Bill Murrell
Member
Thanks Nige. With your expert guidance the machine will live again.