No parking brake?
 

I finally got around to finishing the brakes over the weekend. I had purchased rebuilt calipers from Rockauto a while back.

After finishing everything I noticed no matter how much I adjusted the parking brake the lever was very easy to pull. Turns out the parking brake on the passenger side is not engaging. The cable pulls, the lever rotates but the piston doesn't move in the caliper. Normal hydraulic actions works just fine though.

My understanding is something is wrong with the self-adjuster in the caliper. Not having a parking brake on that side isn't a big deal but I'm curious if this will cause other brake problems if I don't fix/replace the caliper.

This issue happened to mine once before as well as only one wheel engaging, I bled the calipers and had no further issues. It's been years since worked with this but I believe there were two bleed screws and I opened the upside-down one on the bottom, I remember that because it didn't make any sense to me.

Anyways I figured this all out after needlessly replacing a caliper that ended with the same results as before. Looked into it and it was too simple :banghead:

I thought the parking brake was purely mechanical.

I never understood why the calipers have two bleed valves. Ironically, the passenger's side is the only one I attempted to bleed with the bottom valve out of curiosity. I still bled both rears with the top screw but hopefully it's coincidence that the passenger's side isn't working. I've probably bled the whole system 5 times now with a Motive pressure bleeder and the traditional 2-person method and no luck.

You would think!

I'll double check my manual, I could be wrong.

Interesting... I thought the bottom bleeder screw was there simply there to help purge accumulated crud out of the caliper when pressure flushing & bleeding. Given the way this caliper is designed and oriented on the car, you can see there's a low point that would tend to trap & accumulate crud, so I figured the extra bleeder was there to deal with it.

Whenever I flush & bleed brakes on the FC, for the rears I open the bottom screw first (top closed) to flush out the crud. When fluid flows out clear & clean from there, I close the bottom screw & open the top one to purge the air out.

Double checked my manual and found this but nothing in detail regarding why the bottom is used. .

+1

I agree - it's due to the orientation of the brake caliper being almost vertical.


-Ted

Interesting. Is that in the Haynes manual? I have a paper copy of the FSM and I don't recall seeing that. I'll give it a try because I definitely fall into the category of having "overhauled" the calipers. The worst that can happen is the parking brake still doesn't work. I've discovered some older RX7 racecars have deleted the parking brake system so I'm not too concerned at this point.

EDIT: It shows up in the FSM for the '88 MY but not in the FSM for the '89 MY. More interesting...

On a somewhat related topic does anyone know how to actually adjust the brake pedal "free play?" I've swapped to the 929 MC and booster and the pedal free play is out of spec according to the FSM. The FSM instructions for adjusting pedal height and free play are the same. In order to get the free play in spec I have to adjust the brake pedal all the way out, which puts the pedal height out of spec. I don't see how to get the free play in spec without violating the pedal height spec. Maybe the 929 free play specs are different...

Yes, it's a Haynes manual.

Yeah, weird that it's in the Haynes manual and the S4 FSM's but not in the S5. I'll give that a try. I've also read that a good hard brake from speed in reverse can also dislodge a stuck self-adjuster.

I still can't find anything about independently adjusting pedal height and free play. I currently have free play set within spec but having the pedal all the way out against the stop, which "pre-loads" the booster pushrod to an extent.

So fast forward 6+ months and I'm still diagnosing the problem. I learned something new today: with the piston pushed all the way into the caliper both sides appear to work as normal. That is, rotate the lever and the piston is moved outward about 1/8 in. or so. However, after the piston is adjusted outward to contact the brake pad only the driver's side piston moves when the parking break lever is moved. I'm guessing something is wrong inside the passenger's side caliper.

+1

I agree something is wrong with the rebuilt unit...

Is the unit still under warranty?
If not, why not tear it apart and inspect the bore?


-Ted

Yep, bad caliper. Replaced it with another reman'd unit and everything functions as it should. Too bad the left rear is now leaking so it needs to be replaced (again) as well. I'm going with Centric rebuilds units this time. I've had good luck with them in the past.

I've never under any circumstances had any luck with anything that suckauto has ever sent me.... They're horrid.

I don't have any issues with RockAuto themselves - they're just the distributor. I think the current/bad units were reman'd by Raybestos. The re-replacements are Centric and so far no issues with the right rear (no leaking and the parking brake works). I think the fronts were Centric as well and they seem to be holding up just fine. If they bugger up again I'm buying rebuild kits and doing it myself.