1978 eldorado brake question
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The Classic Cadillac Forum Discussion, 1978 eldorado brake question in Past Cadillac Vehicle Discussion; One last question on my eldo, I do not really know how to deal with a brake issue I have. ...
  1. #1
    unautherized is offline Cadillac Owners Member
    Automobile(s): 1978 Eldorado biarritz
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    1978 eldorado brake question

    One last question on my eldo, I do not really know how to deal with a brake issue I have. The brakes where fine and the rear calipers started having small leaks from sitting, I rebuilt the rear calipers. I bled the brakes well front and rear , The brake light on the dash would not go off, after exhausting all other measures ,like re bleeding and making sure the e-brake was not the problem. I removed the switch from the proportioning valve, but really couldn't do anything to it so I put it back and whalla the light was out, I assumed it was just stuck. I drove the car around fine and then came home and backing it into the garage ,the light came back on. The pedal seemed to drop a little lower at that time and with a couple of pumps it came back higher and solid and the light went off again.
    Just wonder if anyone here has knowledge on the rear calipers enough to suggest that maybe I did something wrong putting the calipers back together,Or if they adjust themselves as far as the e-brake goes, I am thinking that maybe there is more travel in a piston or something that allows the pedal to be a bit low on the fist shot and then its higher after that?? Does this make any sense? Right now the first time you hit the pedal it seems like it travels a little to far and then comes higher with a couple of pumps, it then stays and does not fade at all. I have heard on some cars that the way the rear disc brakes adjust themselves is by using the e brake? Hydro boost fluid is full, Brake fluid is full, I think right now after the car has been sitting the light will come on and the pedal will feel low, then with a couple of pumps it will be high and hard and the light will go off. Any suggestions of what I should try would be greatly appreciated . Thanks

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  3. #2
    carnut is offline Cadillac Owners Master
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    Re: 1978 eldorado brake question

    The inner rear pad has a pin on the back that MUST align with the recess in the caliper piston. That allows the piston to rotate each time the parking brake is applied. That keeps the proper gap pad to rotor surface. You must adjust the piston to the pads after reinstallation of the caliper. That's done by removing the park brake cables from the arm on the caliper and moving that arm back and forth to rotate the piston out. Then reinstall the cables and verify the cables are NOT holding the arm off its rest point on the caliper casting. I use a large screw driver to ratchet the caliper arm. Not done correctly, the rear pads will be too far away from the rotor surface and WILL increase pedal travel.

  4. #3
    unautherized is offline Cadillac Owners Member
    Automobile(s): 1978 Eldorado biarritz
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    Re: 1978 eldorado brake question

    I had a feeling this is something to do with the orientation of the parts, That is very helpful info, I will check things out tomorrow, Thanks very much!

  5. #4
    carnut is offline Cadillac Owners Master
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    Re: 1978 eldorado brake question

    On the cables, once they're back on the arms, adjust the cable trunnion till the arm JUST starts to lift off the cast in rest. Then slightly back off the adjuster nut.

  6. #5
    unautherized is offline Cadillac Owners Member
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    Re: 1978 eldorado brake question

    Well I looked into things today and found that the little pegs on the pads where not lined up with the holes in the pistons, which did not surprise me since I didn't know about them. But I removed the calipers turned the pistons to align with the holes, re installed properly and put the e brake levers on and turned them toward the front of the car and it took out the play in the pads. At that point I am only able to put the lever on on one side so that there is hardly any travel and the other side has a little more travel before applying the brakes. I guess I am missing something . The brakes are working fine, as is the e-brake, and the light is not coming on but the peddle just feels mushee and can be pumped to a higher point. Do I have to apply the and release the e-brake to adjust things or should it have a good pedal now? Maybe I should just go get two new calipers.?

  7. #6
    carnut is offline Cadillac Owners Master
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    Re: 1978 eldorado brake question

    I would repeatedly apply and release the parking brake to hopefully even things out. When I was a service adviser for Cadillac, adjusting the pistons within the caliper had about a 30% success rate. Most times we found it necessary to install "loaded" rebuilt calipers. Loaded meaning calipers with pads already installed.

  8. #7
    70eldo's Avatar
    70eldo is offline Cadillac Owners Connoisseur
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    Re: 1978 eldorado brake question

    I don't know about 1978, but for the earlier models the rear breaks would adjust themselves when you brake repeatedly while reverse driving (backing up)?

  9. #8
    unautherized is offline Cadillac Owners Member
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    Re: 1978 eldorado brake question

    I did a bunch of e-brake on and off cycles, I tried bleeding the rear again just to make sure, using a vacuum pump as before and the pump wasn't pulling fluid with a vacuum on it. So I sucked the fluid out of the rear master reservoir to see if something got stuck in the bottom, It was pretty dirty in there I refilled with new fluid and then the vacuum pump started pulling fluid, I bled some more and a combination of all of the above including some cuss words and mean gestures at the car things worked out so that I have a nice hard high pedal, I drove the car around a little and its great. Thanks so much for all the useful necessary tips, the whole job would have been much easier the first time I knew more about what I was doing. It was a good day, I also took out the gas tank to check the ender because the gauge would bounce around when low. I found a section on the contacts in the sender that dirty I cleaned it all and put it back together the gauge seems to be more stable. Thanks !!!!!!
    carnut, 70eldo and talismandave like this.

  10. #9
    70eldo's Avatar
    70eldo is offline Cadillac Owners Connoisseur
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    Re: 1978 eldorado brake question

    Stick to DOT 3 for your brake system. Do not go higher than 3. The additives in the higher DOTs will slowly eat away the rubber seals (you'll notice black 'clouds' in the brake fluid).

    ...as I assume your 1978 Cadillac needs DOT 3 per specifications?

  11. #10
    carnut is offline Cadillac Owners Master
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    Re: 1978 eldorado brake question

    Quote Originally Posted by 70eldo View Post
    I don't know about 1978, but for the earlier models the rear breaks would adjust themselves when you brake repeatedly while reverse driving (backing up)?
    That only works if the car has "drum" rear brakes. And the self adjusters are lubed.

    ----------

    Thank you for posting the results. It's refreshing to read about a repair where the person knows his way around a car!

  12. #11
    70eldo's Avatar
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    Re: 1978 eldorado brake question

    Quote Originally Posted by carnut View Post
    That only works if the car has "drum" rear brakes. And the self adjusters are lubed.
    When did Cadillac introduce rear brake disks?

  13. #12
    carnut is offline Cadillac Owners Master
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    Re: 1978 eldorado brake question

    I think 1976 Eldorado? 1977 on the Seville.

  14. #13
    70eldo's Avatar
    70eldo is offline Cadillac Owners Connoisseur
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    Re: 1978 eldorado brake question

    Do you know if those brake disks can be swapped to earlier Eldorados somehow? Maybe by swapping the whole rear axle?

  15. #14
    carnut is offline Cadillac Owners Master
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    Re: 1978 eldorado brake question

    The rear master cylinder reservoir (closest to the booster) is for the FRONT brakes. The one furthest from the booster is for the rear brakes. As you apply the brake pedal the rod in the master cylinder displaces the rear reservoir first which squeezes the front pads. As you continue to depress the pedal, eventually the rear pads are squeezed.

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