mrmonk7663

iTrader: (9)

I recently rebuilt my brakes. I also changed out the lines. The master cylinder appeared to be empty after disconnecting the lines and calipers. I bled the brakes today. Brake pedal sucks. My question is this. A. by disconnecting the lines and calipers, and seeing the master cylinder apparently empty, will air have been introduced into the ABS unit? If the answer is yes, how can I go about removing the air? Will putting the car on jack stands, with engine running and rear wheels moving, and engaging the brakes, cycle the abs pump and push out the air into the brake lines, where as I could then stop the engine, and bleed normally? Any help would be appreciated. I have heard of this technique being used for the NB Miata, but I never heard mention of a master cylinder that was dry or a master cylinder that was being replaced etc.

thanks,
mike

codrus

One option is to bleed, then go out and engage the ABS, then bleed, then repeat a few times. That works for some people.

It didn't work for me, so I figured out the ABS diag procedure -- it's at the end of my ABS build thread here: https://www.miataturbo.net/build-thr...into-nb-73579/

Alas, it still didn't make a really good pedal. Next on the list is swapping in a 929 1" master cylinder.

--Ian

TNTUBA

iTrader: (1)

I use the "up on jack stands" method on my car. There are a few things you will need to do though:

In order to activate the ABS system you will need to spin one of the front tires until it reaches a high enough speed to cycle the ABS start diagnostics. You will be able to hear the relays and pump cycle during this test.

Once you get the system "ready" do just what you said. Get the rear wheels rolling 20mph or so and press the brake, add power to keep the rear wheels spinning until you feel the ABS engage.

You will only have about 20 seconds once you start the rear wheels spinning without the front wheels spinning before the ABS light comes on and the ABS will be inoperative until you start the entire process over.

Do this a few times then bleed the system...rinse, lather and repeat.

A Motive power bleeder is also a MUST HAVE when it comes to bleeding ABS brakes IMHO.

My car didn't come with ABS...when I added the system to the car I thought I was NEVER going to get all the air out of the system. That power bleeder made the job a TON easier.

To me this is much easier than jacking the car up, taking the wheels off, bleeding the system, putting the wheels back on, letting the car down, driving it, getting the car into ABS, bringing it home, Jacking it up, taking the wheels off.......................

mrmonk7663

iTrader: (9)

So when spinning the front wheel, you do this while the car is running and no throttle is applied...ie you can do it alone and don't need someone spinning the rear wheels with throttle at the same time you are spinning the front wheel?

Leafy

iTrader: (1)

This is all too much work. Just jumper the correct pin to ground, hold the brake pedal, and turn the key to start diagnostic mode and make the pump cycle once.

mrmonk7663

iTrader: (9)

Yep. Did that this morning. Piece of cake! Thanks

codrus

So did it help with the pedal feel?

--Ian

mrmonk7663

iTrader: (9)

I will report back on it this evening. This morning I only jumpered the pins and verified cycling of the ABS. I did not bleed after that. I will in a few hours though.

mrmonk7663

iTrader: (9)

Pedal now feels great. Took the car out...bedded the new pads to the new rotors, and all feels well. The JUMPER method does work. I can confirm this. If you never had air enter the ABS, then you don't need to worry about the jumper method....but if air did make its way in...then its an invaluable trick. Here is a pic of a bent paper clip being used as a jumper. With jumper in place....push brake as far as it will go and hold....turn key to ON position...a few seconds later the abs will cycle audibly...when it finishes release brake and turn off key.

I bled first, then used the above method, then bled again, then used the above method one more time just for good measure. The last time no air came out of any lines while bleeding which let me know that the ABS had no air left in it either.

Neddy

Thread dig.

So just to be sure, if you use a motive (or similar) power bleeder you don't need to 'cycle' the ABS?

Mobius

iTrader: (2)

No. You still cycle the ABS, but with the power bleeder applied. If I recall correctly from doing it to my car, it's been 18 months, I did the following:

Apply power bleeder
crack first caliper screw
cycle abs
close caliper screw
repeat for other 3 wheels, refilling master cylinder as necessary between wheels.


You have to cycle the ABS no matter what method you are using, if you want to be thorough, and/or have reason to believe air has gotten into the ABS computer.

Neddy

ok, cheers.

I went ahead and did it with the motive bleeder without cycling ABS computer and it seems to have worked perfectly, but I don't believe that I have any air in the ABS pump.