Tried to do my brakes today. Forgot about the epb system sort of and engaged the parking brake by accident with it not installed on the brake caliper. The motor turned until it extended the piston as far as the motor could which essentially is beyond the edge of the piston and oring seal for the brake piston. What ended upo happening is all of the ball bearings on the lead screw fell out and the entire assembly had to be taken off the car. There are tiny springs too and I cannot figure out how to put it back together. Damn! This is going to be expensive since I cannot find anything to explain how these things are put together, what the part number is or any pics.
I am posting pics to show what one actually looks like inside. It is a ball bearing lead screw design and the entire brake assembly rides in a pressure housing based on o-rings only. The balls are not the issue, the little springs are. If I knew what to do with them I could put it back together. I also cannot find anything online for parts to buy just the EPB lead screw piston as it rides inside the actual piston. Interesting engineering but somebody forgot to include a mechanical stop in the design to prevent it from unscrewing itself and all the bearings from falling out. Frustrated!
As you can see in the pics, the inner piston is threaded and has grooves for ball bearings like the shaft does. It is literally a lead screw. The lead screw piston part sits inside the actual hydraulic piston. The lead screw shaft goes through the piston housing in the caliper and out the other side. It is emersed in hydraulic fluid and protected by O-Rings. How it assemble it generally is easy. What to do with all the little springs...not easy... two long ones. 7 short ones. The long one looks slightly damaged.
Volvo Brake Diagrams do NOT show these parts. Makes me think they come already installed in the caliper and are not intended to be field serviced. Sucks for me. Might cost me $200!
![Image]()
![Image]()
![Image]()
![Image]()
![Image]()
![Image]()
![Image]()
![Image]()
![Image]()
![Image]()
I am posting pics to show what one actually looks like inside. It is a ball bearing lead screw design and the entire brake assembly rides in a pressure housing based on o-rings only. The balls are not the issue, the little springs are. If I knew what to do with them I could put it back together. I also cannot find anything online for parts to buy just the EPB lead screw piston as it rides inside the actual piston. Interesting engineering but somebody forgot to include a mechanical stop in the design to prevent it from unscrewing itself and all the bearings from falling out. Frustrated!
As you can see in the pics, the inner piston is threaded and has grooves for ball bearings like the shaft does. It is literally a lead screw. The lead screw piston part sits inside the actual hydraulic piston. The lead screw shaft goes through the piston housing in the caliper and out the other side. It is emersed in hydraulic fluid and protected by O-Rings. How it assemble it generally is easy. What to do with all the little springs...not easy... two long ones. 7 short ones. The long one looks slightly damaged.
Volvo Brake Diagrams do NOT show these parts. Makes me think they come already installed in the caliper and are not intended to be field serviced. Sucks for me. Might cost me $200!
