Hello all...
The Story:
I put a set of 4 piston calipers on my '89 N/A (Non-ABS)... Before doing this I called Autozone or Oriellys and asked if the Convertable master and the Regular Master where the same part number... The guy said yes... Now that the calipers are on and I have bled the dog snot out of the brake system I have brakes that will build up when pumped with the car shut off, just like they should... I start the car and they dive to the floor... I can pump them up to get a little braking power, but its barely enough to stop a bicycle... I called both oreilly and autozone and now they are telling me the part numbers are different on the master cylinders...
My questions...
1. Do I have to change the master cylinder or is there something else causing the crappy brakes?
2. If I have to change the masters; Will the turbo or convertable master fit onto my regular booster?
3. I left my rear calipers as the originals on the car... Do I need to change the proportioning valve?

 

The proportionning valve is the same on all of them, the 4 pot brakes came with both sizes of MC's. That's not the problem. The problem is that there's still air in the system. Try opening it and pumping continuosly for a number of strokes, rather than doing the open, pump, close routine.

Bleed it untill it's hard.

 

^ What he said.

I just did the swap on my '89 GTU and it took four (4) rounds of bleeding to get all the air out. I pushed nearly a quart of fluid through the lines before all the air was gone. Speedbleeders help to make this a less annoying task.

The pedal feel after swapping to the four-pots is at least as good as it was with the old single-pots, and maybe even better. Of course, the fact that the old brake components were 18 years old might have something to do with that...

-chris

 

Cool... Thanks...

I bled them twice... And went thru (1.5) 32 oz. bottles of brake fluid... All of my calipers where rebuilt and the mc is only a few months old... I will bleed them again and see if it helps...

 

I've seen 3 people make this mistake, so try not to take offence....... Are you sure you put the calipers on the correct sides? The bleed nipple must be on the top of the caliper (where the air will go). If you install the calipers on the opposite sides to where they should go, the nipple will be on the bottom, and you'll never be able to bleed them properly. Just a thought.

 

My car--> <-- Me... ... No offense at all... I think I did exactly that... I think I put the nipples on the bottom... I will check it tonight when I get off of work...

 

I know someone who did that and I've heard of others doing it, so you're not the only one (if that is what happened).

 

I just checked it and sure enough... The bleeder valve is on the bottom... I am about to go out and swap them...

 

Hey... I wanted to thank everyone for their help... Sure enough that seems to have fixed the problem... When I got done it was rock hard and there did not seem to be much stopping power but after I drove it a little bit it went opposite... I got softer and had more stopping power... I will bleed it again and that should probably do it...

Again... Thanks again for all of the help...