I recently bought a used John Deere 5045e tractor for agricultural work, and until today there were no problems with it. However, just the other day I noticed problems in the braking system: when the brake pedal was pressed, the tractor did not stop immediately. At the same time, the brake pedal is not pressed to the full depth, as if something is holding it. Unfortunately, the problem could not be fixed, so I ask the specialists to tell me what to do?
This is generally a sure indicator that air has entered the brake lines. The way this happens most often is if you are losing some fluid somewhere and then the reservoir in the master cylinder got too low and air is being pumped into the lines. Another way that can happen is if you have a leak and air is sucked into the line through that. Typically, if this happens, it is just before a complete brake failure.
The first thing is to check the level of the master cylinder. If okay, the next thing to do is bleed the brakes on each wheel.
In general you have to remove the wheel / tire, and look at the rear of the brake assembly. Look where the brake line enters the brake assembly, the bleed valve is typically a small zirk (it looks like a zirk greese but it isn’t one) right near where the brake line comes in. The bleeding usually requires two people. One of them pumps the brake and then keeps the brake pedal depressed, another opens the bleeder valve until it is bled and then closes it before the other person releases the pedal and pumps it again. You will have to do this on each wheel until there are no air bubbles and only pure liquid comes out. Make sure to keep the master cylinder full or almost full while you do this.
After that, if you don’t have air bubbles coming out of the brakes on either wheel and you have a good fluid supply, then chances are your master cylinder or power assistant has gone bad.