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No brake pedal pressure??

G

grasseater

NAXJA Forum User
Location
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This weekend I pulled my front and rear axles to have 4.56's installed and to swap in a D44. Got everything back together today, bled the brake system, and still no pressure in the pedal.

When the vehicle is turned off, you can pump the pedal up to get pressure. When it's started and running, no pressure builds up in the system & the pedal goes to the floor.

The 44 has all new drum brakes (12" vs. the 10" on the D35). I also put new pads on the front calipers.

Any ideas? The brakes worked fine as of Thursday night when I pulled the axles (and disconnected the brake lines).
 
I am having a similar issue after I pulled both axles to do various upgrades (d30/d44) then put them back in and bled the system (I've even resorted to using a pressure bleeder to assure they were bled) still have very little preassue on the peddal. Are you getting absolutly no pressure or just a little? I can still drive mine and make resonable stops but it feels like something is still off. When I push in my peddal to just before it hits the floor and hold it I can hear a Slight hiss like there may be a vacuum leak of some sort ...

-Joe S.
 
JoeXJ said:
I am having a similar issue after I pulled both axles to do various upgrades (d30/d44) then put them back in and bled the system (I've even resorted to using a pressure bleeder to assure they were bled) still have very little preassue on the peddal. Are you getting absolutly no pressure or just a little? I can still drive mine and make resonable stops but it feels like something is still off. When I push in my peddal to just before it hits the floor and hold it I can hear a Slight hiss like there may be a vacuum leak of some sort ...

-Joe S.
Click to expand...

I get pressure when the vehicle is off, i.e., pump the pedal up, bleed, etc. When the engine is running, I get significantly less, if any, pressure in the system. I can hear a slight hiss coming from the booster/ master cylinder area, but no fluid leaking. Weird. I'll let you know when I find a fix. Thanks for the reply.
 
There is no bleed fitting for the master cylinder.

You bleed it by removing the fittings where they come out the side. Take a couple of short (8" to 12" long) lengths of universal brake line with the same fitting, screw them in, and bend them up in a loop so the open end extends about half way down in the fluid reservoirs of the master cylinder. Then pump the peddle until no bubbles come out.

If you changed to a D44 with 12" brakes, it probably uses a much larger wheel cylinder. Your master cylinder may not be capable of pushing enough fluid before it bottoms out. Or your combination/proportioning valve may have bought the farm.
 
Actually your problem sounds more like a brake booster problem. Check your vacuum. As for bleeders, I use a electric vacuum bleeder. The vacuum works better than pressure. A vacuum causes the bubbles to get bigger and they purge out easier.

If you have a big vacuum leak, check your idle rpms. If they are high or surge, bingo.
 
old_man said:
Actually your problem sounds more like a brake booster problem. Check your vacuum. As for bleeders, I use a electric vacuum bleeder. The vacuum works better than pressure. A vacuum causes the bubbles to get bigger and they purge out easier.

If you have a big vacuum leak, check your idle rpms. If they are high or surge, bingo.
Click to expand...

Before I disconnected the brake lines, everything was fine. How about this for a cause of my problems:

When I bled the system, I opened the first bleeder @ the passenger rear, then had my helper press the brake pedal to the floor, then closed the bleeder valve. After doing this three times, fluid came out. Popular opinion says that this caused me to blow the seals in the master cylinder.

The way they are supposed to be bled is pump the brakes up, THEN crack the bleeder till fluid starts out, then close.

What do y'all think? I'm pretty confident it's not a vacuum leak b/c all was well before I disconnected lines and the idle is perfect.
 
rebleed them
your assistant may have let off too soon pulling air back into the line.

pump to get pressure at each wheel, bleed each at least four times, starting with the rear pass, then tha rear drivers, then the front pass, then the front drivers, check the master cyl between wheels make sure it doesn't get low then repeat the procedure...

even if you have already re-bled them do it again to be sure
 
Something else that can help with bleeding brakes are SpeedBleeders (yes, there is a website: http://www.speedbleeder.com and you may be able to get them locally) or a bleeder kit with a check valve.

The only problem I've found with either of these is that the valve won't open if you've got a big air bubble in the line.
 
grasseater said:
I get pressure when the vehicle is off, i.e., pump the pedal up, bleed, etc. When the engine is running, I get significantly less, if any, pressure in the system. I can hear a slight hiss coming from the booster/ master cylinder area, but no fluid leaking. Weird. I'll let you know when I find a fix. Thanks for the reply.
Click to expand...

Figured it out: Front calipers were on the wrong sides. Funny how gravity works...if the bleeder valve is under the brake line, air will hang in the top of the caliper.

Swarmi Marmi says bleeder valves must be above brake lines.

Will confirm tomorrow when I have a helper to bleed the system, but $ says this fixes it.
 
Im in the same situation. I replaced the master, brake booster, and the line that blew. Have absolutely no pressure to petal. To the point that i can use my pinky finger to press the petal to the floor. Thinking it could be the ABS module? Can someone point me in the right direction? Thanks!!
 
Twisted orthodox said:
Im in the same situation. I replaced the master, brake booster, and the line that blew. Have absolutely no pressure to petal. To the point that i can use my pinky finger to press the petal to the floor. Thinking it could be the ABS module? Can someone point me in the right direction? Thanks!!
Click to expand...

Did you bench bleed the master cylinder with it totally horizontal? Did you cap the proportioning valve lines after MC removal?
 
Sounds like master cylinder to me also. I saw a vid on Youtube where a dude claimed you could bleed your master cylinder by opening up your driver's side front caliper bleeder and slipping a tight fitting hose over it that run directly back into the master cylinder, and slowly pump the brakes while making sure the hose stays below the fluid level in the master cylinder. Thoughts?
 
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