Braking problems

Discussion in 'E9 Projects and Restorations' started by Drew Gregg, Jan 17, 2019.

  1. Drew Gregg

    Drew Gregg Member

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    First time I drove my '73 3.0CS about 15 miles I noticed the engine lugging like the brakes were all activated.
    Then I stopped for about 1/2 hour at a store and all was normal. Another 15 miles and I'm now in 3rd gear trying to keep up with traffic. Then I lost all braking as my foot went to the floor. I found out the fluid had not been flushed in 13 years! Now the brake calipers and clutch slave have fresh Redline fluid and a few miles in the cool night and all is normal. The old fluid looked like it was 13 years old. Today I drove about 40 min and 10 miles to a shop and I could feel the engine lugging again. After about 30 minutes I drove home and the brakes were again normal until going about 10 miles,down-shifting at every light to keep off the brake pedal. The brakes locked up again and all 4 wheels were very hot. You could smell the brake compound. Has anyone had this problem? What's next? Master Cyl.? Booster? Proportioning valve? All 4 calipers were totally free when cold when I had the car up on the jack stands. And then all 4 were hot and locked up. And the brake pedal had very little play and was hard to press when the problem occurred. All suggestions are appreciated.
     
  2. eriknetherlands

    eriknetherlands Active Member

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    No expert, but somewhere I feel however that the culprit is central, and not wheel (corner) dependent. If all 4 corners go good or bad at he same time, that's too much a coincidence for me.
    and if they are locked up it means that either the pistons are held there by friction at the piston (brake pistons in the caliper are stuck; happens especially after longer stand still), or by pressure behind the piston.

    I've heard that the flexible lines just before the caliper can turn soft and block internally.
    Not sure if that is the case here (i'd expect the flex line to block the flow to the caliper, not block the flow back from the caliper to the pedal), but if my flex lines were 13 years old; i'd replace them anyway. If they aren't a problem now, they will be soon (they crack and rupture catastrophically).
    You might just solve your problem along the way. if not then at least the investment still was usefull.

    On the other hand, if there is continued pressure behind the piston that cannot flow back to the reservoir it should show up if you open a bleed valve with engine shut off and foot off the brake. iIf brake fluid comes out, then something's wrong preventing the fluid going back. Where could that pressure come from? No i'm not expert in master cylinders, boosters and other bits, so I'll leave that route to others, as I am sure others here know those components better then I do.
     
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  3. sfdon

    sfdon Well-Known Member

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    Sounds like your Brake master is not releasing pressure when you take your foot off the pedal. With front wheels in air spin front tire by hand. Then pump brakes 20 times and try to spin. If now it’s tight- use an 11mm wrench to release pressure to caliper. If wheel now spins it’s line or master. If still tight it’s caliper.
    My bet is master is bad.
     
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  4. m_thompson

    m_thompson Active Member

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    Mine had the same symptoms. Replacing the flexible lines fixed it.
     
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  5. Drew Gregg

    Drew Gregg Member

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    I appreciate your reply. I forgot to state that all 4 wheels have stainless flexible lines.
     
  6. Drew Gregg

    Drew Gregg Member

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    The flexible lines are all stainless.
     
  7. Drew Gregg

    Drew Gregg Member

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    I think your bet is correct since the drag is happening on all 4 wheel calipers once everything is hot after 10 miles of driving. The flexible lines are stainless. I'll jack up the front and try your idea on the left front wheel by cracking open one of the stainless lines after pumping the brake pedal. The system will not be hot,however. The 4 wheel lock-up released the brakes after just sitting for 5-10 minutes in the driveway after those 10 + mile rides.
     
  8. Gary Knox

    Gary Knox Well-Known Member

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    It may also be possible that the really old fluid, with a lot of absorbed water may have caused rust in all the pistons F & R. They would be slow to release, and there would be constant rubbing of the pads on the rotors. Turning puts different angular stresses on the rotors, which then could have pushed the pads back slightly - thus they 'seemed' OK after turning into a parking area. Further braking/driving after leaving the area would result in more slow heat build up. Just a thought.

    IF that is the cause, rebuilding calipers is not difficult. I'm sure there are good YouTubes on it.

    Good luck.

    Gary
     
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  9. Gary Knox

    Gary Knox Well-Known Member

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    A short PS: It may be that no all four of the brakes are 'dragging'. Next time you drive it and the engine struggles after ~10 miles, stop and get out. Put some saliva on your fingertip (or some other liquid, or a leather glove). Put the finger through the wheel so you can touch the rotor. If it is hot, that brake caliper pistons are not retracting. If all are hot, then you know it MAY be the master cylinder, and not individual (1, 2, 3, or 4) calipers. Try turning the front wheels sharply in highway speed a couple of times and do not apply the brakes. IF i it seems to have more power but still not full power, then the rears may be dragging. If it seems to have full power, then only one or both of the fronts are not fully retracting and dragging.

    Gary
     
  10. Drew Gregg

    Drew Gregg Member

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    Gary--your suggestions are good ones. I did much of the same by measuring the temps of all 4 wheels/rotors. They were all hot. The car can't be pushed while in neutral and the engine off. I'm going to replace the master cylinder and check the pedal linkage to make sure nothing is hanging up. Driving the car again to get these symptoms is not worth the danger of being in our urban traffic.
    I grew up in Delaware Valley. Used to drive my '64 Triumph Spitfire in the country roads around Springton Reservoir and Westtown lake when I wasn't fishing in them. Graduated from Drexel in '69. Next time I visit my mom up the there,we need to meet. Drew
     
  11. Gary Knox

    Gary Knox Well-Known Member

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    Drew,

    I'll look forward to hearing the results that give you 'brake free' cruising!!

    Yes, by all means, send me a 'conversation' with contact info a few weeks in advance, and we'll try very hard to work out a time to get together. I live about 3 miles straight west of the County courthouse.

    Cheers,

    Gary-
     
  12. Sven

    Sven Well-Known Member Site Donor

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    Given the importance of braking I would also rebuild all calipers regardless. You say the fluid has sat there for 13 years. Was the car being driven during that time? Do you know when and if the calipers have ever been rebuilt? Replace the master and all flexible lines & rebuild the calipers, period.

    Note, that the stainless steel flexible lines are just rubber (or some synthetic material) lines wrapped in a woven stainless so they will age and crack like rubber.. The main advantage of ss lines is that there is some exterior protection to the hose and the ss wrap restricts the expansion of the rubber hose during braking.
     
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  13. Peter Coomaraswamy

    Peter Coomaraswamy Well-Known Member Site Donor $

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    Just another thing to check, so I had this exact same problem, even the driving time intervals were near identical. The culprit IS the master cyl., but the question is why?? The master is not releasing pressure from the calipers, here is where you have to start looking- is it a bad master (in your case likely so-per Don, and per Sven- calipers could probably use a rebuild) however in my case the nut that locks the adjustment for the physical pedal height was loose and it eventually backed its way to the full break-on position (how could I forget to tighten such an insignificant part). This was fairly easy to find for me because the pedal had little to no downward movement. I made the proper adjustment and have not had the problem again and I did a couple 100+ mile trips subsequent to the repair.

    Best of luck and let us know what finally caused the issue.
     
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  14. Drew Gregg

    Drew Gregg Member

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    The car was driven about 300 miles/year. The rear calipers were new in 2005. The front calipers were rebuilt in 2005. the stainless lines were installed in 2005. I replaced the master cylinder but can't seem to get the air out of the system. Going to bleed them for the 3rd time soon.
     
  15. Drew Gregg

    Drew Gregg Member

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    I replaced the master cylinder. The brake drag seems to be gone. The pedal goes to the floor and I need to pump it to stop after the first power vacuum bleed. Then I did a manual bleed and the pedal was a bit more firm,but still not correct. I'm going to bleed again. Where is the pedal height adjustment ?
     
  16. deQuincey

    deQuincey Well-Known Member

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    when i bought my coupe i replaced all fluids, brake fluid too
    i noticed that the new yellow fluid bright yellow colour lasted very little weeks and started turning brown very fast, my flexible lines and calipers were also redone by PO around 2005, but they did not changed anything else, so dirt was inside
    it took me six years of replacing the brake fluid yearly to get a yellow durable colour in the reservoir
    brake fluid is 10 euro for 1 liter
    so i invested 60 euro to solve the problem
     
  17. deQuincey

    deQuincey Well-Known Member

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  18. Peter Coomaraswamy

    Peter Coomaraswamy Well-Known Member Site Donor $

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    Hi Drew, the pedal height adjustment is attached to the back side of the brake pedal, but I think you have an "air in the system" problem. I sound like a cheerleader for this product but EVERYONE SHOULD HAVE ONE!!!! this will allow you to bleed
    brake and clutch easily and by yourself bleeder.jpg
     
  19. Drew Gregg

    Drew Gregg Member

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    I used a vacuum type power bleeder to replace the 13 year old dirty fluid. Then I did the old fashioned 2 person pump the brake & clutch pedal method. Then I replaced the master cylinder and bled the system 2 more times after driving with the soft pedal around the neighborhood. The last time ,I still found bubbles in all 4 calipers. The new master cylinder had more air in the system than I expected. Now the brakes are fully functional with no dragging after a 10-15 mile trip at highway speeds. Your "Power Bleeder" pushes fluid from the reservoir?
     
  20. HB Chris

    HB Chris Well-Known Member Site Donor $$

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    Drew, yes. This is the one I use that we discussed. I’ve always felt that pressure bleeders at the caliper suck in air as soon as the nipple is cracked open. Glad you finally got it resolved.
     

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