10aebuild

Hi guys,

Just bought a 10AE and the first thing on the agenda (fluids/filters aside) was to freshen up the brake system.

When I drove the car during the test drive, the brakes had a slight pulsation and the pedal goes quite low, perhaps 2/3's the way down, before I feel resistance. Also, slightly more than avg force is required to the bring the car to a stop.

It felt exactly like any car would when the pads/rotors are down to minimal specs.

Things aren't so normal once I purchased the vehicle and had a closer look with the caliper taken apart. First off, the ABS has been disabled by what looks like rerouting/looping of hard lines. There is no signs of leakage and everything looks pretty solid. I have my fingers crossed that this little 'mod' has no influence on my problem at hand.

What surprised me was that the rotors/pads actually have 40-50% remaining according to factory specs, front and back. One of the four pistons on the passenger front was seized as well. Given that my pads/rotors are only half gone .. I know my problems are beyond simple rotor/pad replacement.

I went ahead and replaced the pads/rotors all around and got both the front calipers rebuilt by a caliper rebuilder. (Midwest Caliper) Bled the system, and just as I thought, nothing has changed. Pedal still goes quite low before I hit resistance and it still requires slightly more than normal pressure to bring the car to a stop.

Looked through the FSM and did some checks. I don't have any of the diagnosing tools required (vacuum/pressure gauge, 3000+psi hydraulic pressure gauge) so I was only able to do the simple checks and of course, its none of those. There is no visible signs of leakage anywhere as well.

FYI the following are the checks I performed and results:
Pumping the pedal with engine off then start engine with pedal depressed, pedal should go down. yes it does.

Warn engine then switch off, depress pedal, each stroke should be shorter than previous. Yup.

Start vehicle then hold the brakes down. Turn engine off while still holding down pedal, pedal should remain the same height and not sink. Yup.

The fat vacuum hose from the booster, disconnect from engine side. Air flow should only be allowed to travel towards engine side. Well .. I don't have a vacuum/pressure tester ... so I kinda extended the hose and used my lungs .. seems to have passed that too.

Now I'm out of ideas. My next attempt would probably be replacing the old flex lines. They looked pretty old with some cracks on them. But from experience, I have not seen a car with old enough flex lines that can swell/flex to the point where it will eat up the pressure from 1/3 brake pedal travel. Is this possible?

Or perhaps I'm wrong about the ABS bypass? Somehow its losing pressure? Doesn't make sense logically to me since I don't believe hydraulic systems can lose pressure over distance. But then again I'm no engineer nor have I traced each and every line to ensure proper placement.

What should I do next? Any help/comment will be greatly appreciated.

Thanks

Ken

mar3

iTrader: (8)

Let's see what some 2ndgen guru's have got to say...I know we have some lurking.

Mario III

johnny O

I'm no 2nd gen guru, and not even sure what a 10AE is, but I am familiar with many types of ABS systems. Soft pedal is usually air in the lines if travel stops at same place consistently.The pulsations are warped rotors, but you didn't mention if you felt the pulse in the steering wheel or brake pedal, and if brakes would pulse with light application of e-brake only. Helps determine is warpage is front or rear. This is important because if the ABS hydraulic assembly has been bypassed, you may have only front or rear braking. There are two hard lines from the master cyl to the ABS module, then FOUR lines out to the individual wheels. If two of the four are left out of the hydraulic circuits, you may have only front brakes, or only rear brakes, or only one front and one rear brake functioning. Any one of these conditions would certainly lead to quick rotor warpage and pad wear as well as a long pedal with reduced stopping power. Start by identifying each hard line from the individual wheels at the module and label LF, LR, RF, RR. Next id and label the two lines from master cyl. as R(closest to booster) for Rear, and F for Front. Examine "custom" routing to see how and where hydraulic pressure is being distributed. Be sure that none of the lines are without a source of pressure from the appropiate master cylinder source. Are any of the ABS unit outputs looped back into the module? Is the module plugged into the wiring harness, and is the ABS yellow light on? You mentioned that you had the Factory Service Manual. There will be an extensive description of operation and diagnosis provided, including a routing schematic for hydraulic distribution. Experience recommends R&R ABS unit and route lines per FSM for correct repair. Your life may depend on it.

10aebuild

Thx for your input Johnny,

The pulsation at the pedal was from the old rotors. I will take a closer look at the ABS bypass job and post an update. I know I'm getting braking on all four corners because I was able to bled the system, and the wheels do 'lock' when I apply the brakes with the car in the air.

Aaron Cake

iTrader: (1)

It can take a considerable amount of time to get all the air from the 4 piston calipers. Inevitably, no matter how much you bleed them, after a short trip there will be a lot of air liberated from the system requiring another bleed. That may be some of your soft pedal problem.

The ABS bypass should not cause issues if it is done correctly.

Another thing to check is pedal freeplay. There is an adjustment inside the car to correct this.

10aebuild

It can take a considerable amount of time to get all the air from the 4 piston calipers. Inevitably, no matter how much you bleed them, after a short trip there will be a lot of air liberated from the system requiring another bleed. That may be some of your soft pedal problem.

The ABS bypass should not cause issues if it is done correctly.

Another thing to check is pedal freeplay. There is an adjustment inside the car to correct this

Thank you Aaron for your advice!

The ABS bypass checked out good according to the FSM and to the best of my knowledge.

There WAS pedal freeplay which caused about a full inch extra pedal travel.

After bench bleeding the MC, and the 4 corners again I had regained about 85% pedal stiffness. Just when I was about to give up, I decided to bleed 4 corners again but this time with the vehicle running. For some reason, that did the trick for me.

Pedal feels pretty damn good now. Thanks to all that had given me help and advice along the way. For those out there having trouble with sloppy pedal, I would strongly suggest bench bleeding the MC. Someway, somehow .. air gets in there .. and bleeding it in-car does NOT have the same effect as bench bleeding, as least not for my car.

Thanks again RX7Club!

Ken

johnny O

Ken, Glad to hear you got to the top of your pedal and the bottom of the problem. Sharing your experience will certainly help others."O"