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Lost Power Brakes

Discussion in 'Roadster: Technical' started by Tex EV, Feb 14, 2017.

  1. Tex EV

    Tex EV Member

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    Location:
    Houston, TX
    Drove the Roadster through some unusually heavy rain this morning. Got to the office, parked, and went about my day. When leaving for lunch later, I noticed that the friction brakes were doing almost nothing. The brake pedal was stiff, just as it is when the car is off. Managed to drive 80 more miles like this today, mostly depending on regen braking to slow down. To bring the car to a full stop required almost standing on the brake pedal. No warning messages displayed. I realized while pulling into my driveway that I was no longer hearing the brake vacuum pump when releasing the brake pedal at low speed.

    Car is currently in the garage and partially disassembled to get to brake system parts. Here's what I've checked so far:
    Fuse 22 (brake pump) - Good
    Vacuum line between brake pump and master cylinder - Connected on both ends
    Brake pump - Electrical connector w/ black and green wires is seated properly

    Wondering how the vacuum pump is triggered - is there a switch on the brake pedal assembly?
    Is there a simple way to test if the vacuum pump itself is operational?
    Anything else I should check?

    Thanks in advance!
     
  2. MLAUTO

    MLAUTO Member

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    The connector at the pump should have 12V with the key on. The pressure switch that controls the pump is part of the pump itself. I would check the connector and pump terminals to make sure they didn't get wet and burn up. If they are OK and have voltage, then you will need to remove the pump.
     
    • Informative x 1
  3. Tex EV

    Tex EV Member

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    I got the pump out about an hour ago, tipped it on its side, and saw water begin dripping out of the electrical connector :(. The rubber grommet that is supposed to fit over the connector was hanging off, apparently allowing water to seep in. I disassembled the pump and got it cleaned up. Turned the internal mechanism by hand and verified that it pulls vacuum. There wasn't a ton of water in there... hopefully no damage, but I'm about to cross my fingers and plug it back in.

    Anyone know if the bead of black sealant is supposed to be there? Doesn't look very "factory".

    IMG_20170214_225651.jpg IMG_20170215_162206.jpg
     
    • Informative x 1
  4. efxjim

    efxjim Member

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    Location:
    Glendale, CA
    I had this happen several years ago. Your vacuum pump electronics in the bottom of the pump housing may have gotten wet. The circuit board is not coated very well against moisture and the housing leaks water that cannot drain away. It is not hard to remove the pump and get to the pc board. I dried mine out and cleaned it with distilled water and a tooth brush. It tested fine when cleaned up. I then coated it with several coats of conformal coating to protect it in the future. I then fabricated a protective boot for the pump to ward off water and included a small drain hole/breather in the bottom. It has been working fine for the last 30k miles and saved me about $700 on a new pump.
     
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    • Like x 2
  5. efxjim

    efxjim Member

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    Black sealant was on mine as well.
     
    • Informative x 1
  6. Tex EV

    Tex EV Member

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    Plugged it back in, turned the key, and heard the familiar increasing-pitch hum! Brake feel is back to normal, but won't be able to verify stopping power until the car is back on the ground. Now to reassemble everything.

    Any chance you have pictures of this that you could share? Would be great to see!
     
    • Like x 2
  7. efxjim

    efxjim Member

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    Congratulations! Sorry no pictures. The area the pump is in gets a lot of mist/water. seal it up best you can and possibly add a weep hole.
     
  8. thefortunes

    thefortunes Member

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    @MLAUTO Sent you a PM on a different matter. Please let me know if you got it. Thanks!
     
  9. Tex EV

    Tex EV Member

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    I think I won the award for unluckiest/idiotic Roadster owner of the day. Just got the working vacuum pump back together and sealed up with a fresh bead of silicone, then decided I would drill a weep hole at the bottom of the electronics housing... :eek::mad::oops:
    Looks like I'll be spending $700 soon.
    IMG_20170217_201409.jpg
     
  10. spaceballs

    spaceballs Member

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    IC doesn't look like it's cracked, just scratched.
    Looks fixable, to me, any good EE guy should be able to fix that.
     
  11. Tex EV

    Tex EV Member

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    I'm not an EE guy, but I tried. Looks like the drill took out one of the solder pads, so I'm not sure how that would be fixed.

    Been pondering a few options...
    1. Bite the bullet and order a new OEM pump.
    2. Try to reuse the original pump with an external pressure switch - seems the only purpose of the internal circuit board is to tell it when to turn on/off.
    3. Try an aftermarket setup with a vacuum reservoir.
     
  12. MLAUTO

    MLAUTO Member

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    Unless you like spending money, just get an aftermarket switch for $35 and bypass the damaged board.
     
  13. spaceballs

    spaceballs Member

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    If you like, PM me your email, I'll have my EE guy do it for you then.
     
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  14. Tex EV

    Tex EV Member

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    PM sent! Tesla just informed me that there are 12 of these pumps left in the nationwide parts inventory. Would be ideal if this one can be salvaged.
     
  15. IirisSeveri

    IirisSeveri Banned

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    What's one of the scariest things that can happen while driving a car. How about No Brakes! Brake failure can occur without warning. You stomp down on the brake pedal to apply the brakes and nothing is there. The pedal goes all the way to the floor and there are no brakes.

    What can you do? Scream? Pray? Try pumping the brake pedal as fast as you can. It might generate enough pressure to apply the brakes and stop your car. If nothing happens, apply the parking (emergency) brake as hard as you can. It should start to slow your vehicle immediately. If you can't react quickly enough and are in danger of crashing into another vehicle, look for a way to avoid the collision. Blare your horn and try to steer your way around other vehicles or obstacles. Eventually your vehicle will coast to a stop. Pull over to the side of the road, shut the engine off, put the transmission into Park (or leave it in gear if it is a stick), set the parking brake and call for help. DO NOT attempt to drive your car until the problem that caused your brakes to fail has been diagnosed and repaired.
     

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