NoOne

I did a search and found no one mentioning how to bleed brakes with ABS.

I just got the car back from the shop and the pedal requires pumping before good braking action. First pedal depress and you go 60 percent down to get 40 percent brake effectiveness.

Second pump you go 20 percent to get what I assume to be 100 percent effectiveness.

The shop said they bled the brakes, however I asked them how they bled the ABS unit and they said it was not neccessary. Every ABS car I've seen requires the unit to be cycled during the bleeding process.

I have to do this tommorow, putting new rear pads on and its possible I need to bleed the slave also.

Right now I'm more concerned about the brakes, this is a LS1 conversion so the clutch setup might be different.

Brakes work fantastic on second effort, just need it on the first.

Thanks

rynberg

The FD braking system always seems more effective on the second pump. There are no special procedures to bleed the brakes on the FD.

https://www.rx7club.com/showthread.p...t=bleed%2A+abs

NoOne

ok, I read the thread on the ABS portion. I didn't realize that the Nippon unit is always open.

How to fix the double pump then? There has to be a reason as to why it happens and a fix.

I read the Stoptech article on pads shifting and although it may be true, still unacceptable for street use.

I'll rebleed them today after replacing the pads. This isn't just a matter of effectiveness on the second push, the first push feels like total mush, then the second good braking.

I can't imagine Mazda released the product like this, they'd never pass any motor vehicle safety standard, al of that is based off of one depression of the pedal.

There has to be a reason its like this.

Mike Nola

I was told by a mazda trained RX7 mechanic to switch the ignition to "run" while you bleed the brakes.

DZeckhausen

That doesn't do anything! The only time your various ABS valves open and close is:

• during the self-test cycle at around 3mph after you first start driving
  
• During a driving situation when the ABS engages as a rsult of the wheel speed sensors indicating impending lockup
  
• When the Mazda diagnostic computer is connected and issues a command to the ABS valves to cycle and the accumulator pump to turn on

The problem is most likely that you have some air remaining in the brakes and your service shop didn't use best practices for bleeding. They probably just hooked up a pressure bleeder and moved some fluid through the system rather than JOLTING the fluid with a 2-person bleed technique such as the one described on my web page: http://www.zeckhausen.com/bleeding_brakes.htm

djantlive

there is nothing special about bleeding abs brakes. It's the same as non abs cars. what is the point of this tread??

particleeffect

some (all?)ABS units hold a small amount of fluid IN them, closed off from the rest of the brake system, and alot of these units need to be cycled "open" to get that extra fluid out of the system.

so yeah, it's different.

the important note is weather or not the ABS in our FD's is closed or open by default. if it's closed, then it will need to be opened somehow. seems to be some conflicting info on this aspect of our ABS units.

-edit. unfortunately, the Mitchel shop manual did not answer this question either, with no reference to the default state of the ABS unit. and a very brief bleeding info section.

NoOne

I bled the brakes with the key on as mentioned and the problem went away entirely.

You can hear the ABS unit pop open when you turn the key on.

malhall

When the vehicle manufacturer builds an ABS equipped vehicle the ABS unit is supplied to him "dry". He then uses a vacuum purge to ensure that all the air is removed from the system prior to filling with fluid. If you buy an ABS unit from your dealer, perhaps as a replacement to a faulty unit, then it should come to you wet i.e. full of fluid, to aid bleeding after fitting. Any attempt to use a vacuum purge would result in immediate contamination of the vacuum system rendering it useless. Cycling the system, as described above, during the bleed is very time consuming and would not be used by the vehicle manf. but should eventually be successful.

djantlive

i pump the brake pedal to bleed the brake line. therefore, i have to turn the ignition key on to depress the brake pedal. it's never been a problem for me.

Section8

iTrader: (6)

I did mine yesterday with the ignition turned off, my pedal feels fine (actually much better, my brake fluid had air in it, and was 11 years old!)

NoOne

You won't release any possible air in the ABS system until you actually use the ABS.

There is also the possability there is no air in your ABS.

This was more directed at those who had soft pedals after bleeding.

The fronts seem to be more difficult to bleed just from the standpoint of where the bleeder is located, its very easy for air to get back into the caliper.

Turning the ignition on just opens up the ABS unit and lets the fluid flow through flushing out any air.

After a track day last Friday my fluid has gone black and the pedal softened a bit, I'll rebleed it this week after the speed bleeders show up.