vartok

last week i had the suspention class at the collage im going to replace some parts for me (lower ball joints, lower control arms, wheel bearings) ended up having to put it back together for them with the instructor (class ran out of time) When we sat the car down, the brakes went right to the floor. The brake system was never opened, just the calipers pulled off to the side to get the knuckes out and hung from bungie cords. I got the car back to my shop on saturday and used out bg flush machine to flush the brake fluid (which was black), still no peddle, put a new master cylinder on (yes i bentch bleed it), still no peddle, ran another quart of brake fluid though the flush machine just to make sure there was no air in the lines, and still no peddle.

If i pump the brakes, it will build pressure but then bleed back off. funny thing is, if the engine is off, the peddle will get hard but as soon as i start it it will drop. It kinna sounds like a booster issue, but ive never heard of a bad booster making a low peddle.

JDMswagSerf

It does sound like a bad brake booster if all else was done correctly.

vartok

a few guys locally have suggested that some trash or something is stuck in one of the valves of the ABS pump

JDMswagSerf

Did you bleed the abs pump?

wunfstgsr

check the brake booster vac hose. that goes to the engine. Check for kinked brake lines to the caliper they might have got twisted and put back on wrong or routed correct causing a kink in the brake line.

vartok

Well, the flush machine hooks up to the master cylinder reservoir and pressurized it with a quart of brake fluid behind it. You go to each wheel and open the bleeder valve and wait for the fluid to come out clean. I ran a total of 2 quarts through it, one before and one after the cylinder replacement. So I don't think there is any way there is air anywhere in the system

JDMswagSerf

The abs pump has its own bleeder screw.
When the key is turned on, the abs pump primes fluid(or something like that) and may have sucked air in.
The pump needs to be bled after all sides have been bled.

JDMswagSerf

Try hooking you machine up again and turn the key on, then turn the machine on and open the bleeder screw on the abs pump, then close it.
Do that a few times to get air out of abs pump, unless brake fluid comes out on the first try.

vartok

Thing is, they brakes were just fine before the suspects taken appart and the pistons on the calipers compressed abit to get them back on the rotors, the system was never opened when this problem started

JDMswagSerf

Any visual brake fluid leaks?
If it was never opened, and nothing was torn or borken, I would start looking at the brake booster.
May have just been a coincidence it went out the same time the brakes were worked on.

vartok

actually, they wernt even technically worked on, they were just pulled out of the way to be able to get the knuckle out to replace the wheel bearings.

vartok

still fighting with this issue. ive pressure bleed over and over. put on 2 master cylinders, replaced all the rubber lines and new front calipers (old ones were sticking)

where can i get line plugs so i can start plugging lines to see where the pressure is going?

planning on pluging up the master cylinder to see if it would hold pressure, then move to the abs pump and plug lines one by one... and just work my way down the system.

fcm

Sounds like it may be "blow-by", [seal on master brake cylinder piston is gone].

If you can build pressure and then slowly lose it, but do not lose fluid, the seal is gone and the fluid is just leaking back past the seal into the reservoir.

This happened on my 94 RS, one day it was working, replaced the fluid, and then it started doing that very slowly at first but quickly got worse, I just got a rebuilt one from Lordco. 94

vartok

thats why i put 2 master cylinders on it... i thought the first was bad out of the box