I have a D3C LGP Hydrastat that some time ago started to apply the brake on one side or the other by itself. Took it the the local Cat dealer and for a cool $1,100 they diagnosed that the parking break assemblies need to be replaced to the tune of over $13,000. Now the tractor will not move but a few inches either way. Does the group agree with the diagnosis? Can rebuilt brake assemblies be found and installed? How much of a job is it? Thanks for any light you can shed on my problem. Bill
How handy are you with tools and what sort of facilities do you have to work on the tractor..?
Good shop and handy with yools
Tractor Serial Number..?
5GS00523
Do you have a Parts Manual already..? If not you will need one, if not for this repair then for one in the future. Go to https://catpublications.com/ When the popup window appears click on "Continue as Guest" Put SEBP2686 in the Search window and hit enter. The illustration below should pup up. $89 for a downloadable pdf file. I'll post up some procedures later regarding getting into the brakes.
I have a service manual coming
Good to know. it will be a big help to you. FYI, the Service Manual will not include a Parts Manual
I need to get the brakes released to get the tractor to the shop. Any suggestions?
Is this any help..? If you choose to remove the axle shafts I can post something up.
Will try to remove the axle shafts tomorrow and get it to my shop.
Just be careful, because with the axle shafts removed you will have no brakes at all unless you can run the engine and use the blade as a brake.
Thanks
They don't call them stealerships for nothing. I haven't seen a fault in the brakes themselves not allow them to release. If they were leaking the oil would fill the finals and blow your duocone seals. I'd verify you have pressure going to the brakes to release them before you year it all apart. If it actually is the brakes that are bad they can be rebuilt fairly easily. You're lucky you have a D3 and not a 4 or 5. Drive motors are smaller, lighter and much easier to get out.
The dealership said they checked the pressures to determine it was the brake assemble itself. Sure hope they did
When you get your Service Manual it might just pay you to check before starting to pull anything apart ..........
I need to get it to the shop first. Hopefully today.
The brakes are sandwiched between the drive motors and final drives. One of them will have a hose coming in from the front. A steel line connects left and right and there will be a pressure switch on one of them which goes to the light on the dash. I don't remember for certain but I believe there should be 5-600psi there with the parking brake released. If you don't have pressure then the problem is not the brakes themselves. If either of your final drives are overfull it's likely from the brakes leaking but as I said they'll blow the seals on the final before it could leak enough to not release at all.
Thanks for the info. Will try to get the tractor to the shop next week and check the pressures. Got other priorities on the farm this week. Thanks again.
Nige Got tractor to shop finally. Had a blown fuse in the key circuit which slowed me down moving it. . Found the park brake light bulb burned out. Replaced the bulb and it stays on all the time. Any suggestions?
Had to remove drive axles to move it. Tow valve would not release the park brake
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.
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.
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?
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..?
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.
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).
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.
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?
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.
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.
Thanks Nige. With your expert guidance the machine will live again.