914 rear brake Pressure Control Valve., Install. Options

[914Toy]

I received a refurbished rear brake Pressure Control Valve (PCV) from PMB (excellent service) and installed it today, after reading many of this subject posts here, and thinking about a bleeding process. The following is what worked for me:

1) I started with a very good firm brake peddle before installing the PCV.

2) After loosening the driver side rear brake caliper bleeding screw, I placed a wooden dowel between the seat and the brake pedal long enough ( about 30") to depress and hold the pedal in, about 3 inches - this stops the gravity flow of fluid from the reservoir. Then I re-tightened the bleed screw on the brake caliper.

3) Then I disconnected all three brake lines from the PCV. After pulling the driver side line aside enough (not too much) to give access to the PCV firewall upper mounting bolt, I removed these two bolts holding the PCV to the firewall, and extracted the PCV from the car.

4) After adjusting parallel alignment of the brass "T" on top the PCV, I began installing the valve. First, I connected the passenger side brake line (has better access) finger tight to help align the PCV to the upper two lines. Then I pulled the driver side brake line away from its position (not too much)to give access for installing the upper PCV bracket
mounting bolt (bit of a challenge!). After tightening both PCV mounting bolts, I connected the remaining two brake lines and tightened all three of them.

5) Now to the infamous bleeding! First I removed the wood dowel which allows the brake pedal to return to rest position, which allows gravity flow of brake fluid to occur when any of the bleeding valves are opened. I returned to the PCV and cracked the driver side brake line and watched it carefully. Within a minute, after the trapped air in the PCV escaped, brake fluid began to flow a drop per 3 to 4 seconds and I let it flow for about a minute. Then I quickly attached my pressure bleeder to the reservoir and went back to the PCV to observe higher fluid flow - about one drop per second - from the still cracked brake line. After another minute of this flow I tightened the brake line - thus no more fluid flow from the PCV/brake line connections.

6) Now to bleeding the rear brake calipers, with my brake fluid pressure system which pressurises the brake fluid reservoir. After removing about a 1/4 cup of fluid along with air bubbles from each rear brake calipers, I carefully tested the brake pedal action. While not bad, there was still air in the system. I then repeated the brake bleeding as described above, with some very small air bubbles in the exiting fluid. I tested the brake pedal feel again and found the pedal almost back to the starting excellent action. For good measure, I bled the calipers once more - think I saw a few very small bubbles - and found the brakes are back to their original firm action (IMG:style_emoticons/default/smile.gif)

Note: 1) With my bleeding set up, I need to refill the reservoir after each removal of about 1/4 cup of fluid.
2) It appears that pressing the brake pedal between each caliper bleeding cycle helps reposition and thus removal of the small remnant amounts of air in the PCV - I only pressed the brake pedal at about normal firm street driving leg pressure a few times between each bleeding cycle.

I hope this helps (IMG:style_emoticons/default/beerchug.gif)

[tvdinnerbythepool]

Added to my favorites for reference. Thanks!!!

[914Toy]

Quick edit, Item 5) second line: "-- cracked the PASSENGER (not driver) side --"

[76-914]

Good job. Great write up and you've given me an idea. Thx Keith. (IMG:style_emoticons/default/beerchug.gif)

[iankarr]

(IMG:style_emoticons/default/agree.gif) Thanks for taking the time to share. Super helpful!