GetBoosted

I'm having some trouble with my brakes after replacing my brake lines with some stainless steel lines from Corksport and bleeding them using a Motive power bleeder.

My car is a 1988 RX-7 GXL with 4 piston calipers.

Here's the process I went through:
* Replace all 4 brake lines (still some fluid in the reservoir since not much came out) with stainless steel ones
* Turn ignition to on position with the engine off
* Fill the power bleeder with 1 liter of DOT 4 Synthetic Racing Brake Fluid
* Pressurize bleeder (attached to brake reservoir) to 15 psi
* Bleed brakes in this order: Passenger side rear, Drivers side rear, Passenger side front, Drivers side front
* Check brake pressure at the pedal (engine still off) and the brakes are very firm
* Turn the engine on and take it out for a spin, the pressure in the brake pedal is now squishy and the brakes are dragging

What did I do wrong and more importantly... how do I fix it :-).

Thanks!

clokker

iTrader: (2)

Still air in the system...rebleed.

What is Step #2 all about?

Black Knight RX7 FC3S

iTrader: (7)

if you are using pressure to bleed the brakes, for the rear, I would bleed them till atleast 5 ounces of fluid comes out for each rear caliper. Since the front two lines are shorter you can let about 3 ounces out each one.

If its still squishy try doing it the normal way and see if that fixes it.
Also, if the brakes are dragging, that would mean the caliper might be bad. the piston should go back into the caliper by itself after being pressured by stepping on the brake pedal.

GetBoosted

I did step two because that's the way that most people recommend doing a bleed on my Audi so I did it on the RX-7 out of habit.

Air in the system would account for the brakes feeling squishy but not the caliper staying engaged.

GetBoosted

I can try re-bleeding them but both of the front calipers are locked up on the rotors. The back ones are as well but not as bad. How could all the calipers go bad at once? Doesn't make sense to me.

clokker

iTrader: (2)

Yeah, you're right, that doesn't seem likely.
Something is applying pressure to the MC, either the booster or the input shaft at the pedal.
What happens when you disconnect the vac line at the booster?

GetBoosted

I can disconnect the vacuum line tonight and I'll post my findings... What should I be looking to happen when I pull that line?

clokker

iTrader: (2)

Well, you'll hear a hiss as the vacuum in the booster is released and after that...dunno.

As you said, it's very unlikely that all four calipers simultaneously failed, so you need to look at the components of the system that affect everything, which leaves the MC itself, and the booster.

I've never had this happen to me so I have no real idea what's happening.
The idea is to start eliminating possibilities and go from there.

Obviously, the first result you'd like to see is the wheels free up.

Prior to this latest work, what is the history of the system?
Have you ever replaced the MC or booster?

BTW, you don't need the key ON to work on the RX-7 brakes.
Maybe your Audi has ABS which requires power to bleed or something?

GetBoosted

I pulled the vacuum line from the master cylinder and I heard a hiss as expected. I also started the car to insure there was vacuum being applied and there was. However, the brakes are still locked up unfortunately.

As far as maintenance is concerned on the MC and brake booster, I'm not sure since I got the car about a year ago. I've never had issues with it so I never replaced either.

You're right about why I leave the ignition on in the audi. The abs system screws with bleeding the brakes.

Think it's a good idea for me to pull the calipers and reset the pistons? Not sure if that will help or not.

clokker

iTrader: (2)

Well, you could try that but I'm not sure if it'll help.
Something is affecting all four calipers and the only things that could do that are the MC, the booster and the adjustment at the pedal.

Is there freeplay at the pedal?

GetBoosted

No free play in the pedal. It's squishy like it was before but it's not free to move around at all.

Is there any easy way for me to test the booster versus the MC to see if one or both of those are bad?

jjcobm

iTrader: (18)

I have never bled brakes with pressure. Maybe that caused a failure in the master cylinder somehow keeping the piston pushed in? 2 person bleeding never fails.

blackrotary23

i know brakes pretty well. sounds like your caliper(s) are seizing up. best way to tell is drive the car for about 10 consistently applying the brakes, then take it home and use a spray bottle to spray the calipers and whichever ones sizzle up and smoke are the ones you need to replace.

good luck!

clokker

iTrader: (2)

There's supposed to be some freeplay.
Try backing off the adjustment at the pedal and see if the wheels free up.

jjwalker

I had a similar issue when I replaced my master cylinder and bled the brakes.

All the trash and nasty stuff that was up top made its way into my calipers and made the seals stick. I had to pull them off, and work the pistons back and forth to clear the crap from them, and bleed some more. Worked out okay, and thankfully, I didn't lose the caliper piston seals when doing so.

GetBoosted

Ok, I'll pull the calipers this weekend to see if I can get determine if the piston seals are sticking. If I blow a seal out on one I guess I'll just have to upgrade to those nice AP Racing calipers I was planning to put on my other car :-). After I try that, I'll check the pedal adjustment as well to see if that yields a better outcome.