1987 GMC Dump Truck -- brakes engage by themselves
The brakes on our 1987 GMC dump truck are engaging by themselves when they get hot. After about an hour, they disengage and you can run the truck again. We have replaced the master cylinder and booster. We have bled the master cylinder per the instructions and also each brake line as instructed. The brake pedal seems to be working fine (not spongy). The brakes just get hot and engage without pushing the brake pedal.
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the pto should be in constant mesh with a gear on the countershaft and be spinning all the time
the pump is connected when the operator moves a switch to allow air to engage a dog from that engaged gear to the pump
when you say win't engage , is the problem that the gears clash and grate when the switch is engaged or the engagement is smooth but it will not drive the pump
In the first instance put your foot on the clutch to stop the countershaft turning so that the dog gets to engage
in the second instance there is a shear pin to the pump drive that is fitted to prevent the destruction of the gear box if the pump should seize for any reason
Take it to an accredited shop that handles pto installation and repairs
Electrical problem. Something gets hot and stops working. Could be fuel pump or something in the ignition system, so losing spark. After it stalls, spray starting fluid in the intake and try to start. If it fires up and runs a few seconds, you know it's a gas problem. If starting fluid doesn't do anything, check for spark, it's probably an ignition failure-possibly the coil or the ignition control module. The module can be tested at a parts store.
With the dump valve in it is fine to push it, however it is not a good idea to tow the machine as speed will force oil around the systen and try to engage the drive, so sorry you will need to push it slowley.
have a 95 k3500 4x4,when i shifted to 4 hi,would not engage.never once heard any type of noise in the front end.replaced both actuators,fuse is,front will not engage.please advise.ken at 989-560-1906.or email@example.com thanks