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post #1 of 11 (permalink) Old 07-24-2016, 06:55 PM Thread Starter
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Help: No brakes when car is on

I have an issue that when the car is running I have 0 brakes.

I recently had the calipers sent out to be reconditioned by PMB.

I bled the system and there is no air.So I think... When the car is not running the pedal is nice and firm. The second I turn on the car there are no brakes what so ever.

Things I have done:
  1. Pinching off the brake booster. I have more pedal
  2. When releasing the pinched vacuum hose the idle changes.
  3. Check valve is fine. Removed it and air can only go one way.
  4. Pumping the brakes repeatedly while the car is on raises the idle

Can anyone provide assistance on what the issue might be?


Adding a video of what it sounds like when the car is not on.

Last edited by phillipah; 07-24-2016 at 07:59 PM.
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post #2 of 11 (permalink) Old 07-24-2016, 07:24 PM
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you might be on the right track... the vacuum booster is dead.


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post #3 of 11 (permalink) Old 07-24-2016, 07:30 PM Thread Starter
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Well that is my worst fear... So with the car not on and in the air. I spin the front tire and then apply the brakes and it starts to barely slow down. You can definitely hear the brakes engage.

How much stoping force should there be with no booster? Should i try and bleed it more?

Thanks

Last edited by phillipah; 07-24-2016 at 07:33 PM.
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post #4 of 11 (permalink) Old 07-24-2016, 07:54 PM
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Quote:
Originally Posted by Gordon Raymond View Post
you might be on the right track... the vacuum booster is dead.

Gordon, wouldn't the appearance of vacuum assist mean that the booster IS working?

The booster HELPS you brake - it doesn't do anything to firm up the pedal, that is all fluid mechanics.

If you disconnect the vacuum booster all together.. and close the end of that vacuum hose with a bolt (so you're not 'leaking' engine vacuum) you would feel NO difference VS when the car was off.

If its still soft, try bleeding again - maybe the front calipers were put in upside down (it does happen, sides get switched and the bleed nipple is not on top).

I've driven the car with no brake boosting - and the pedal is FIRM its hard but doable to brake this car w/no vacuum assist. My initial suspicion is that its not bled fully or there is a problem with the MC.

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post #5 of 11 (permalink) Old 07-24-2016, 09:03 PM Thread Starter
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Help: No brakes when car is on

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Originally Posted by MNVXer View Post
If its still soft, try bleeding again - maybe the front calipers were put in upside down (it does happen, sides get switched and the bleed nipple is not on top).

I've driven the car with no brake boosting - and the pedal is FIRM its hard but doable to brake this car w/no vacuum assist. My initial suspicion is that its not bled fully or there is a problem with the MC.
For some reason as you stated the brakes were upside down on the fronts... don't know why I did not realize it will now...

I will bleed again in the morning when my help arrives.

So am I understanding you correctly? With a semi firm/ firm pedal when the car is off... can go to nothing even when the bake booster is working?

Last edited by phillipah; 07-25-2016 at 05:36 AM.
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post #6 of 11 (permalink) Old 07-24-2016, 09:33 PM
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I had really hard brake petal but could stop in an emergency. Petal did not go down a bit when she was started, replaced booster. Other one petal to the floor was master cylinder. one or the other but I never tried the bolt trick.
When I did the MC I gravity bled it and had no problems.

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post #7 of 11 (permalink) Old 07-25-2016, 03:53 AM
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Quote:
Originally Posted by phillipah View Post
For some reason as you stated the brakes were upside down on the fronts

This is a good thing! It means you don't have to spend $300 on a new booster chasing down a problem that didn't really exist.



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Originally Posted by phillipah View Post
So am I understanding your correctly? With a semi firm/ firm pedal when the car is off... can go to nothing even when the bake booster is working?
Thats what the booster does, it helps you brake. When the car is off, your foot has to do all the work. With the car on, the booster puts pressure on the MC. If you aren't completely bled, then the booster will compress the MC and make it seem like you have no pedal.

My old Isuzu's brake pedal would drop about an inch when you turned the car on. Same deal here, except that system was bled so after the drop the pedal was firm.

Also, for anyone looking at this in the future, the failure mode for the booster is a lack of vacuum, and never 'too much.'




EDIT:
I just watched your video, and you can see the brake fluid decreasing (ALOT) inside of the reservoir with each pump of the pedal. I would do your bleeding and then monitor that fluid level VERY closely, to make sure that there is no fluid ingress into the booster. It could be a function of not being correctly bled, but in the future if you ever LOSE vacuum, its possible that fluid has bypassed the MC, been dumped into the reservoir, and sucked in through the check valve and burned. This happened to me just recently. The fix is a new MC.
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Last edited by MNVXer; 07-25-2016 at 03:58 AM.
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post #8 of 11 (permalink) Old 07-25-2016, 06:34 AM
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Did you bleed all four calipers?

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post #9 of 11 (permalink) Old 07-25-2016, 04:53 PM Thread Starter
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Quote:
Originally Posted by MNVXer View Post
This is a good thing! It means you don't have to spend $300 on a new booster chasing down a problem that didn't really exist.


Thats what the booster does, it helps you brake. When the car is off, your foot has to do all the work. With the car on, the booster puts pressure on the MC. If you aren't completely bled, then the booster will compress the MC and make it seem like you have no pedal.

My old Isuzu's brake pedal would drop about an inch when you turned the car on. Same deal here, except that system was bled so after the drop the pedal was firm.

Also, for anyone looking at this in the future, the failure mode for the booster is a lack of vacuum, and never 'too much.'




EDIT:
I just watched your video, and you can see the brake fluid decreasing (ALOT) inside of the reservoir with each pump of the pedal. I would do your bleeding and then monitor that fluid level VERY closely, to make sure that there is no fluid ingress into the booster. It could be a function of not being correctly bled, but in the future if you ever LOSE vacuum, its possible that fluid has bypassed the MC, been dumped into the reservoir, and sucked in through the check valve and burned. This happened to me just recently. The fix is a new MC.
Thanks for the information. After your explanation it makes complete sense.

I bled all the bakes thoroughly for a few hours going around the car several times. Even tried to bleed the MC. I don't know if its the bleeders I have but they suck. Opening more than just a crack makes them suck air. I mean just a hair and its moving fluid and anything more you hear it sucking air.

After doing all that. I had brakes again but I was not to happy with them. I knew because the calipers have new seals that those would take some time to wear in. I did expect some sponginess but was not really expecting the amount that they were.

I ended up taking the car to a shop within walking distance and they bled everything again. They did say they did pull a little air out of the system but not much. They are slightly better than they were. I was assured by the folks at the shop to just use them and use them hard and things would return as they were.

Thanks again for your help and the information provided. I am glad that it was nothing major especially after I just finished rebuilding the suspension and drivetrain.

Last edited by phillipah; 07-25-2016 at 04:56 PM.
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post #10 of 11 (permalink) Old 07-25-2016, 08:06 PM
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Quello che ho trovato funziona bene per... Sorry had my phone keyboard in Italian. What I have found works for bleeding the brakes and clutch master cylinder really well- requiring only one person- is the Motive power bleeder. With the European attachment. I pump it up to 20psi and bleed the lines. So far it's worked every time. The S3 brake reservoir and the master cylinder reservoir have the same diameter caps...
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post #11 of 11 (permalink) Old 07-25-2016, 08:09 PM Thread Starter
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Quote:
Originally Posted by MNVXer View Post
Quello che ho trovato funziona bene per... Sorry had my phone keyboard in Italian. What I have found works for bleeding the brakes and clutch master cylinder really well- requiring only one person- is the Motive power bleeder. With the European attachment. I pump it up to 20psi and bleed the lines. So far it's worked every time. The S3 brake reservoir and the master cylinder reservoir have the same diameter caps...


Thanks for the tip. That is my next step. I figure a power bleeder would be better for the next time.
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