Turbo II FC

iTrader: (14)

So my cars been sitting almost 5 years and the brakes arent working properly. Ive replaced the master, and abs unit and still no success. I bench bled the master so thats not the problem. The rears sink when pressing the brake pedal while a friend opens the bleeder valve but on the front the brake pedal does not sink to the floor when the bleeder is opened. Ive compressed the calipers fully and pumped the brakes to see if the pistons are functioning and they are yet I can still turn the hub while someone presses the brake pedal. It seems like my problem is only front related. Ive spent countless hours bleeding the system and even pulled the lines off before the caliper to make sure the lines arent clogged. Ive also turned the key to the ignition on and even started the car while bleeding and nothing has changed. I honestly have tried every measure I can think of and have no success. If anyone has any thoughts id appreciate any help.

kensin

iTrader: (22)

Slave

XLR8

iTrader: (52)

I hope you're using that as a derogatory remark

OP, I would try....

- Replacing the front calipers. www.rockauto.com

- Ensure the calipers aren't swapped. I know it sounds silly but they won't bleed if they have been accidentally put back to the wrong place. I've seen it before.

- I would also consider using a power bleeder if you have replaced the ABS unit. It has some serious hiding spots for air that manual bleeding will have a hard time with.

Hope this helps.

Turbo II FC

iTrader: (14)

The calipers have never been removed from the vehicle. A Motive power bleeder was used and the outcome was the same. I havent tried replacing the calipers but they are moving and clamping. Im leaning more towards the pressure not being high enough to push the front pistons hard enough.

XLR8

iTrader: (52)

If the master cylinder is operating properly, and the lines are free and clear of debris, then the calipers should clamp just fine, given they too are working properly. Your issue is lack of caliper strength on the fronts. Obviously the MC & pedal adjustment is sufficient enough to push the rears. Since you have tried everything else, I would replace the front calipers. It honestly couldn't be much else.

I'll add that I would probably be leaning towards a malfunctioned ABS aswell, but since you have replaced it and you aren't getting any codes, it's probably fine. I'm sure you have done this, but double check the connections and lines on the ABS. Ensure everything is hooked up properly.

Fritz Flynn

iTrader: (263)

I'm no expert but I can't see how the ABS would effect the brakes if the ignition is off unless it was clogged up and then you wouldn't be able to even bleed the brakes.

If you can bleed the brakes by pushing the pedal all the in then close off the valve releasing and repeating at all four corners and then pressing the brake pedal and it feels firm and the front calipers are not compressing the brake pad on either front side then the only reasonable explanation is all four front pistons are somehow jammed up which I've never heard of.

Take one of the front calipers off while someone presses on the brake lightly and slowly and see if the piston/pistons are coming out I'd obviously be careful not to push them all the way out if they are indeed moving out. If they're moving out then I don't know what's wrong and can't help. If they aren't you know you need new calipers and I can send you some good ones for 150

Turbo II FC

iTrader: (14)

Fritz, the brake pedal doesnt feel as firm as it should. When the car is on it has very little pressure (I know this is due to the brake booster working) and goes towards the bottom easily and fast. Ive compressed the calipers fully to where they arent touching the brake pads and had someone pump the brake pedal and sure enough, the pistons move and start to grab the pads. I dont see how this is possible but could it be the brake pads are so low that it cant clamp them enough? The brake pads are thin. I highly doubt that just because the pistons should have tons of pressure to the point they want to shoot out but its something ive considered since I dont have many options left besides buying calipers.

XLR8

iTrader: (52)

If the pads are low it WILL affect pedal travel. I can't remember if the FD has an adjustment, I know my FC does. I constantly have to adjust it as the OEM pads wear quickly. The piston rod itself should turn and lock, just as the clutch adjustment.

BlackTruenoAE86

iTrader: (3)

I had the same problem with a faulty master. I would try replace the pads and use an industrial bleeder. When bleeding the front does the brake fluid come out with no bubbles?

Turbo II FC

iTrader: (14)

Brake fluid does come out without bubbles.

XLR8

iTrader: (52)

Here is a test....

Remove one of the rears that is working properly, remove a front and swap them. Let it just sit on the rotor. Bleed as you did before and see if it clamps. If it does, it's definitely the caliper, otherwise, it's a hydraulic issue with the front.

It's been awhile since I rebuilt my calipers and I can't remember if the hydraulic lines are the same on how they attach to the calipers from front to rear, so you may need to pick up a fitting.

Fritz Flynn

iTrader: (263)

Well that explains it

You need a new master cylinder.

I think you said you replaced it but sometimes rebuilt models don't work properly/leak pressure.

It could always be air in the system so if that the case after pumping the pedal up it should remain firm if that's not the case and you're not leaking fluid anywhere it's the master.

Turbo II FC

iTrader: (14)

Hmm ill try the caliper swap method soon. The fittings do attach differently in the front. Also Fritz, so the pedal should feel the same stiffness regardless of the engine being on or off? It was my understanding it would feel different due to the fact that when the engine is off there is no vacuum booster assist so the pedal would be stiffer. The pedal has significantly less resistance when the engine is running but it remains constant.

XLR8

iTrader: (52)

I don't think it's the booster, but here is another test series, just in case.....

-Disconnect the booster from the vaccum line going to it. Attach a line with no check valve. Pull vacuum on the line with a pump that has a gauge on it and a check valve after the gauge (most mityvac types do). The booster should hold relatively the same vacuum for 30 seconds or more.

some other tests:

- Hold the brake down with the car off. start the car, still holding the pedal. The pedal should go down further.

- Note how far from the floor the pedal comes when the car is running. Let the car run, then turn it off without touching the brake pedal. Wait 30 seconds and press on the pedal. It should go down the same distance, then slowly get stiffer each time that you press it again.

Also,

Make sure to check the vac lines from the intake manifold. I had the similar issue. The car had the brake recall done BUT not done correctly by Mazda. The actually added the new check valve (off the booster) without removing the old one on the passenger side.

To do the recall correctly you must replace the hose/check valve on the passenger side with the hose only and the hose on the booster side is replaced with a hose/check valve.

Fritz Flynn

iTrader: (263)

When I say stiff I mean you can't push it to the floor period unless you're applying loads of pressure and intend to break something.

The brake and clutch pedal share the same reservoir but the res is gravity fed to the slave so even if the slave is bad it shouldn't effect brake pedal feel.

Of course the brake booster allows for a softer pedal feel but it operates on vacuum not electricity but even so you should not have issues with the front brakes not applying pressure whether the car is on or off.

Again if I had to guess at this time it's your master however you're still not answering my questions but lets start with something easier

1) If you apply hard even pressure does the pedal go to the floor or stay firm/doesn't go to the floor?

Turbo II FC

iTrader: (14)

When pressing the brakes the pedal does not go to the floor all the way. It stops at about 50% if I'd have to guess before there is solid pressure.

Fritz Flynn

iTrader: (263)

OK we are now back to brake calipers or your leg is weak and it's the brake booster

Turbo II FC

iTrader: (14)

Also xlr8, I've checked the vacuum check valve and it was stuck closed but I applied vacuum and unstuck it free. Also I checked both lines and I do have the relocation of the valve by the booster and they removed the one by the manifold so that's ok.

Fritz Flynn

iTrader: (263)

so it's not:
the booster
the master
leaking lines
leaking calipers etc...

Pull one of the front calipers and do as I suggested earlier and post the results.

Again it would be really strange to have both front calipers jammed up but that's the only conclusion I can come up with.

Turbo II FC

iTrader: (14)

Hah ok I guess I'll buy a rebuild kit since $35 isn't too much.

Fritz Flynn

iTrader: (263)

Before doing that though pull the caliper off and see if the pistons are in fact stuck in place.

Turbo II FC

iTrader: (14)

Just an update. I finally had time to work on my car and it seems the reman master cylinder is the problem. A friend made a pressure tester with some fittings and a gauge to measure the pressure coming out of the master. The front line is not holding any pressure when applying the brakes. We took it a step further and swapped the lines from rear to front etc and the fronts are now clamping down. Thanks everyone for your help. Time to order yet another master lol.

amp

iTrader: (50)

might as well move up to the 929 mc..

Turbo II FC

iTrader: (14)

I was just thinking the same thing.