Bleeding the Brake Proportioning Valve, Please post your "Secrets" here Options

[Brian Mifsud]

I have unsuccessfully attempted repeatly to bleed my brake system and get a firm pedal. I've rebuilt all four calipers, and installed a rebuilt 19mm master. The rubber lines have been replaced with Stainless Flex lines.

I've run literally quarts of brake fluid throught the system using an "Eazy Bleed" at each caliper and still the "soft pedal" persists (can't lock up if life depended on it)

I have not yet replaced the hardlines that run through the body and I know those things can neck down with corrosion over time causing a big pressure drop.

Last on the list of suspects is the proportioning valve.

Are there special "Tricks" that work in getting all the air out of this thing?

I've yet to take it out of the car and take it apart.

[bd1308]

ah

okay here's what you need

ready?

You need to get big bubbles out first. I used clear aquarium hose with a one way water valve in the middle and pump like hell until big bubbles go away

start from rear right and then work your way around

RR, RL, FR, FL

start with BOTTOM bleeder, then top bleeder.

Ive started with a EMPTY brake fluid resivour by accident (rebuilding brakes and dripping brake lines)

after the big bubbles are gone, you need to pump the brakes (gently DO NOT DO NOT bottom brake pedal) until firm
then while someone holds brake pedal down, loosen bleed screw.

do all 4s

that should result in firm brakes.

b

[root]

Brian, Here's a long shot!

When you rebuilt the front calipers then reinstalled them you may have switched them (left one on the rightside and right one on the leftside). If so, the bleed valve would be located at the bottom of both front calipers instead of at the top. If the bleed valves are on the bottom the gas bubbles will hide in the top of your caliper. If the bleed valves are on the top, BUBBLES BE GONE!

root (IMG:style_emoticons/default/beer.gif)

[Brian Mifsud]

ah

okay here's what you need

ready?

You need to get big bubbles out first. I used clear aquarium hose with a one way water valve in the middle and pump like hell until big bubbles go away

start from rear right and then work your way around

RR, RL, FR, FL

start with BOTTOM bleeder, then top bleeder.

Ive started with a EMPTY brake fluid resivour by accident (rebuilding brakes and dripping brake lines)

after the big bubbles are gone, you need to pump the brakes (gently DO NOT DO NOT bottom brake pedal) until firm
then while someone holds brake pedal down, loosen bleed screw.

do all 4s

that should result in firm brakes.

b

Hi B,

What you lay out sounds like my normal procedure except the part about NOT bottoming out. It isn't "typical", but it's happened... what happens when you "bottom out"? Isn't it just the end of the full stroke?

I like the idea of adding an actual one way valve. The "Eazy Bleed" is just a hose in a bottle that stays submerged, so bubble come out, but don't go back in. I havent seen this type of valve in autoparts.. is that an aquarium part also?

[Brian Mifsud]

Brian, Here's a long shot!

When you rebuilt the front calipers then reinstalled them you may have switched them (left one on the rightside and right one on the leftside). If so, the bleed valve would be located at the bottom of both front calipers instead of at the top. If the bleed valves are on the bottom the gas bubbles will hide in the top of your caliper. If the bleed valves are on the top, BUBBLES BE GONE!

root (IMG:style_emoticons/default/beer.gif)

Good point on possible switch... I always assumed it was the rears.. but it's an easy one to check.

[bd1308]

Yeah but without PRESSURE small bubbles dont get expelled.

when you have no pressure, use small brake pumps, dont bottom the pedal out or else you'll damage the MC.

b

[TravisNeff]

As I understand it, you crack open the inlet to the prop valve as someone is pressing the brake pedal down, to let the bubbles out and a little fluid (use a rag over the inlet), then move to the outlet and do the same. bleed, bleed, bleed.

How are you bleeding the brakes? suction, two person method or pressure?

[Brian Mifsud]

As I understand it, you crack open the inlet to the prop valve as someone is pressing the brake pedal down, to let the bubbles out and a little fluid (use a rag over the inlet), then move to the outlet and do the same. bleed, bleed, bleed.

How are you bleeding the brakes? suction, two person method or pressure?

Using Pressure, Solo, "EazyBleed". Also tried vacuum method with same.

[TravisNeff]

Get another person to help you manually bleed (2 person method). It takes a lot of pressure ot overcome the spring in the prop valve. Most probably more than what suction or pressure methods will provide.[code]

[bd1308]

Exactly, thats key.

Using the manual 2 person method + my one way valve speed vleed system, I bled my brakes from an empty brake fluid resivour. I accidentally ran out.

Happened Three times too.

b

[GeorgeRud]

I'm a big fan of the Speedbleeders, they seem to work very nicely and do what they say they will. I've had the best luck with using two people, one pumping the pedal and the other adding additional fluid to the master cylinder as it starts to go down. Then, I use a lot of brake fluid. If you want, Ford Truck brake fluid has a very high boiling point and is cheap, so you can push a lot of fluid through the lines to get rid of bubbles. Then if you want to change to ATE blue or your other favorite brake, do so after getting all the bubbles out.

Getting someone to tap on the calipers while they're being bled seems to help get rid of bubbles that may be clinging to the inside surfaces, I use a small ball peen hammer.

The proportioning valve should actually have it's own bleeder, a design flaw in my opinion. I simply removed them from my cars, and have great pedal feel in both of the cars.