14 replies to this topic

[Scottie]

Hey guys,

Another question for the wizards.....

I have put new calipers on all four corners. After doing so, I went to bleed the brakes. When bleeding the rears, the brake pedal would start to get a stiffer feel, as if pressure was building (completely normal). When we moved to the fronts, we got nothing. the pedal felt like crap the whole time, even when there was no air coming out. So I figured, maybe the master cylinder went a little dry when doing the calipers and "sucked" some air in and it needs to be bled. So, I bled the master, and still the same problem continued. So I figured, the master cylinder is probably 20 years old, Ill get a fresh one. And that I did. After attempting to bench bleed it with the crappy bench bleed kit/plastic plugs it came with, I ultimately bled it once it was on the car. Then went to bleed all four corners, and I still have the same problem! The rears seem as if they are able to build some pressure, but I get nothing from the fronts. Is this a proportioning valve issue? Do I still have gobs of air in the lines?

Also, another point is that if I pump the petal like a madman, it will build a weeee bit of pressure. then if I wait a couple seconds, its all gone when I push the petal again (while the car is off).

I am mind boggled. Please help. I need brakes to stop the car when the race ends.

Thanks guys!

[Glenn]

Hey guys,

Another question for the wizards.....

I have put new calipers on all four corners. After doing so, I went to bleed the brakes. When bleeding the rears, the brake pedal would start to get a stiffer feel, as if pressure was building (completely normal). When we moved to the fronts, we got nothing. the pedal felt like crap the whole time, even when there was no air coming out. So I figured, maybe the master cylinder went a little dry when doing the calipers and "sucked" some air in and it needs to be bled. So, I bled the master, and still the same problem continued. So I figured, the master cylinder is probably 20 years old, Ill get a fresh one. And that I did. After attempting to bench bleed it with the crappy bench bleed kit/plastic plugs it came with, I ultimately bled it once it was on the car. Then went to bleed all four corners, and I still have the same problem! The rears seem as if they are able to build some pressure, but I get nothing from the fronts. Is this a proportioning valve issue? Do I still have gobs of air in the lines?

Also, another point is that if I pump the petal like a madman, it will build a weeee bit of pressure. then if I wait a couple seconds, its all gone when I push the petal again (while the car is off).

I am mind boggled. Please help. I need brakes to stop the car when the race ends.

Thanks guys!

Have you tried gravity bleeding the backs then fronts and see if fluid comes out?

[Bench Racer]

When all four brake lines have been removed/opened simo the is air in all four lines. When we bleed the brakes we always start with the longest line first, the the second longest line all the way to the shortest line. The shortest line being the left front. The two longest lines are the rear lines.

The master cylinder has two seperate pistons with a spring in between. The rearward piston is for the rear brakes. The frontward piston is for the front brakes. When we pump & bleed the rear brakes we get a good pedal at about half way.

When we then move to the front & bleed the front we don't get a pedal improvement & or we don't get fluid flow out the front bleeders. The reason is the the brake pedal is only allowed to move downward untill the rear brakes are fully applied stoping the pedal downward movement. We do not get a long enough or full pedal travel (to the floor) to move the fluid through the front part of the brake system.

At this point in the bleeding process there two proven methods to complete the bleed process.

Method A. Gravity bleed the front brakes. Put a catch bottle on each front caliper & crack the bleed screw loose. Check the bottles each 10 minutes.

Method B. Have two people support you. One person is the brake pumper. Start the front bleed with one bleed person at the long front line caliper bleeder & one bleed person at a rear caliper bleeder. After pumped solid, both the front & rear bleed people crack & close their bleeders simo. Then simo bleed the short front line.

There are other methods using pressure or vaccum bleeders along with modified brake line method that allows the rear line brake fluid to return to the master cylinder. The return to master cylinder lines would be illegal in Spec Miata.

[Scottie]

David,

Very good info to know. I have never gravity bled anything. How do I know when it is bled of air if it is just dripping into a catch can?

[Bench Racer]

David,

Very good info to know. I have never gravity bled anything. How do I know when it is bled of air if it is just dripping into a catch can?

You'll start having a better/fuller/shorter pedal. Sometimes a bubble or several bubbles like to hang around where the front brake line travels UP from the master cylinder, then travels HORIZONTAL & DOWN to the RF caliper. Those last bubbles require some two person bleeding to get the bubbles to travel that hrizontal distance & DOWN to the caliper.

I have installed a T in the HORIZONTAL RF brake line for a brake pressure gauge which is legal. I crack the gauge fitting to bleed the last few bubbles out of the RF brake line.

Different strokes for different folks.

[Scottie]

Thanks for the info. The only thing that concerns me is that when I try to bleed the fronts, I am getting fluid out of them. However it doesn't seen like as much fluid from the rear.

[LarryKing]

Is it possible that the system is sucking air/leaking somewhere?

[Scottie]

Tonight I am going to recheck my nuts and bolts to make sure everything is snug and not leaking.

[Keith Novak]

Did you install speed bleeders by any chance, especially ones that came out of your old calipers?

[Scottie]

No speed bleeders. I am just using the valves.

[Randy Thieme]

Defective caliper? Front and rear brake lines switched on the master cylinder? Overtightened bleed valve? I forget the torque rating on the bleed valves but it's pretty low, low enough I have to use a small torque wrench rated in inch-lbs.

[Scottie]

Ahhhh ladies and gentlemen. To avoid headaches, read the "R" and "L" on the calipers. It makes a huge difference.

[Glenn]

Ahhhh ladies and gentlemen. To avoid headaches, read the "R" and "L" on the calipers. It makes a huge difference.

DOOOPH... I hate when that happens. LOL

[Jim Drago]

DOOOPH... I hate when that happens. LOL

OMG.. That is funny! we have done that before too:(

[Scottie]

I am reliefed to know I am not the only one lol