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Eric_Taylor
Samba Member
Joined: January 21, 2011
Posts: 291
Location: Bend, Oregon
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 Posted: Sat Mar 28, 2020 4:18 pm Post subject: Leaking Brake Booster? Or is this the MC? |
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So I go out to the van (91 Auto 2wd 300K +, but well taken care of) and there is a puddle of brake fluid on the drivers floor mat. Crap. Time to investigate. I shine a lighten the bottom of the booster and it's wet. That says to me the booster is shot, but upon further research, it seems like (1) the booster is not supposed to have fluid in it and (2) the MC to booster seal is the most common leak like this. Today I pulled the instrument cluster out and felt around under the MC there is a residual mess, but it's mostly dried, so obviously old. The bottom of the MC remains actually wet. I'll also add that the MC was replaced in the last 20k miles, but with an aftermarket unit.
Here are a couple pics. The puddle looks bigger than it was because I drove the van as a test and my feet pushed it around. The test was fine as well. Brakes felt normal. Fluid level is good.
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bluebus86
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Joined: September 02, 2010
Posts: 11075
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Eric_Taylor
Samba Member
Joined: January 21, 2011
Posts: 291
Location: Bend, Oregon
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| Posted: Sat Mar 28, 2020 5:31 pm Post subject: Re: Leaking Brake Booster? Or is this the MC? |
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| bluebus86 wrote: |
if that is brake fluid, the brakes need repair, regardless of how they feel.
Bug On, Stopping Well. |
Completely agreed. Thoughts on the right repair? |
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82westyrabbit
Samba Member
Joined: March 02, 2015
Posts: 969
Location: Ma
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| Posted: Sat Mar 28, 2020 5:58 pm Post subject: Re: Leaking Brake Booster? Or is this the MC? |
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| That might be a leaking clutch slave cylinder. A much easier job. That is where my van was leaking a week or so ago. John |
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Ahwahnee
Samba Member
Joined: June 05, 2010
Posts: 9810
Location: Mt Lemmon, AZ
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| Posted: Sat Mar 28, 2020 6:11 pm Post subject: Re: Leaking Brake Booster? Or is this the MC? |
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| 82westyrabbit wrote: |
| That might be a leaking clutch slave cylinder... |
Looks like he has an automatic. |
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bluebus86
Banned
Joined: September 02, 2010
Posts: 11075
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| Posted: Sat Mar 28, 2020 8:29 pm Post subject: Re: Leaking Brake Booster? Or is this the MC? |
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| Eric_Taylor wrote: |
| bluebus86 wrote: |
if that is brake fluid, the brakes need repair, regardless of how they feel.
Bug On, Stopping Well. |
Completely agreed. Thoughts on the right repair? |
either the master is leaking, the tubing us leaking, or fittings are leaking, or the reservoir is leaking, given the location of the puddle of fluid.
you may wish to clean up the spill and observe for leak source. if the tubing or master is leaking, you may only get a leak when the brakes are being activated, or pressurized, hence cycle the foot pedal a bunch of times. After clean up of spill, wedging a paper town in strategic places, and then observe if towel soaks up fluid, perhaps directly under the reservoir.
Make sure the brake tubes are secured such they have not chaffed to a point of leaking nothing should rub on them. check the seals between master an reservoir, look for cracks in reservoir. unbolt mater from booster, if booster is flooded, that is a very good indication that the master has leaked via its piston seals, if so the booster need be cleaned out, flushed with water and dried, and the master replaced or rebuilt
be sure to remove all traces of brake fluid on dash, floor, etc it will strip paint, ruin gage faces, promote corrosion on metal bits, fuse panel, electrics, etc...
So clean up the mess really well, and observe for leak source, check for defects, if none visible, pull master and check inside booster.
Bug On!
_________________
Help Prevent VW Engine Fires, see this link.....Engine safety wire information
Stop introducing dirt into your oil when adjusting valves ... https://www.thesamba.com/vw/forum/viewtopic.php?t=683022 |
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Eric_Taylor
Samba Member
Joined: January 21, 2011
Posts: 291
Location: Bend, Oregon
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| Posted: Sat Mar 28, 2020 9:01 pm Post subject: Re: Leaking Brake Booster? Or is this the MC? |
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bluebus86 - This is excellent. I will get to it and start identifying the issue.
What does it take for the brake booster to actually fail? Based on your list, it looks like that's not likely the culprit. Any way to confirm that it's operating correctly? |
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bluebus86
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Joined: September 02, 2010
Posts: 11075
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| Posted: Sat Mar 28, 2020 9:23 pm Post subject: Re: Leaking Brake Booster? Or is this the MC? |
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| Eric_Taylor wrote: |
bluebus86 - This is excellent. I will get to it and start identifying the issue.
What does it take for the brake booster to actually fail? Based on your list, it looks like that's not likely the culprit. Any way to confirm that it's operating correctly? |
here is a tutorial, and how to inspect and test
https://axleaddict.com/auto-repair/Bad-Brake-Booster-Check
Try the pedal test as detailed in the link above.
But keep in mind a failed booster will not cause a fluid leak. but you might as well test the booster now, verses perhaps replacing a leaky master, then finding the booster has ALSO failed, as the master must be removed when booster is replaced.
Bug On
_________________
Help Prevent VW Engine Fires, see this link.....Engine safety wire information
Stop introducing dirt into your oil when adjusting valves ... https://www.thesamba.com/vw/forum/viewtopic.php?t=683022 |
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swissarmychainsaw
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Joined: March 02, 2019
Posts: 279
Location: San Francisco
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| Posted: Sat Mar 28, 2020 9:36 pm Post subject: Re: Leaking Brake Booster? Or is this the MC? |
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It sounds like you have diagnosed this accurately as brake fluid, but I would just make sure its not water from recent rains (mine tends to puddle there).
if you're sure it's brake fluid, then 100% it's the master cylinder that is causing it and not the booster. They should not have fluid in them, and are just a vacuum 'pump' really.
There are several online vids of 'how to test a brake booster' but I'll tell you now, if your pedal feels ok, your booster is fine. Also points to the MC.
MCs can leak and still "work ok" - meaning pedal feels ok an brakes work.
Obviously you don't let it go though.
Just replace the MC and bleed the brakes.
I just bought a "pressure bleeder" and feel this is 110% worth it. |
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82westyrabbit
Samba Member
Joined: March 02, 2015
Posts: 969
Location: Ma
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| Posted: Sat Mar 28, 2020 9:51 pm Post subject: Re: Leaking Brake Booster? Or is this the MC? |
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| I did not look at the picture close enough. That van is a automatic. It must be the master cylinder then. John |
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bluebus86
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Joined: September 02, 2010
Posts: 11075
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| Posted: Sun Mar 29, 2020 5:50 am Post subject: Re: Leaking Brake Booster? Or is this the MC? |
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| swissarmychainsaw wrote: |
It sounds like you have diagnosed this accurately as brake fluid, but I would just make sure its not water from recent rains (mine tends to puddle there).
if you're sure it's brake fluid, then 100% it's the master cylinder that is causing it and not the booster. They should not have fluid in them, and are just a vacuum 'pump' really.
There are several online vids of 'how to test a brake booster' but I'll tell you now, if your pedal feels ok, your booster is fine. Also points to the MC.
MCs can leak and still "work ok" - meaning pedal feels ok an brakes work.
Obviously you don't let it go though.
Just replace the MC and bleed the brakes.
I just bought a "pressure bleeder" and feel this is 110% worth it. |
if the master leaked into the booster, then the booster should be removed and the fluid drained out of it, and then rinsed, this is important you should not leave the booster alone if fluid is in it, i.e. simply replace master and bleed is not the correct thing to do.
_________________
Help Prevent VW Engine Fires, see this link.....Engine safety wire information
Stop introducing dirt into your oil when adjusting valves ... https://www.thesamba.com/vw/forum/viewtopic.php?t=683022 |
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MarkWard
Samba Member
Joined: February 09, 2005
Posts: 17153
Location: Retired South Florida
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| Posted: Sun Mar 29, 2020 6:22 am Post subject: Re: Leaking Brake Booster? Or is this the MC? |
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I have cleaned brake boosters in place. Water will neutral the brake fluid. Suck out as much fluid as you can. Rinse with water and repeat a few times. Then let it dry out either in the sun or compressed air and or heat gun. Install new master and seal. Then bleed.
But before you tear into it. There are 2 rubber grommets under the fluid reservoir that can leak when temp swings.
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swissarmychainsaw
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Joined: March 02, 2019
Posts: 279
Location: San Francisco
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| Posted: Sun Mar 29, 2020 7:42 am Post subject: Re: Leaking Brake Booster? Or is this the MC? |
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| bluebus86 wrote: |
...
if the master leaked into the booster, then the booster should be removed and the fluid drained out of it, and then rinsed, this is important you should not leave the booster alone if fluid is in it, i.e. simply replace master and bleed is not the correct thing to do. |
This is sound advice! |
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Eric_Taylor
Samba Member
Joined: January 21, 2011
Posts: 291
Location: Bend, Oregon
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| Posted: Sun Mar 29, 2020 12:13 pm Post subject: Re: Leaking Brake Booster? Or is this the MC? |
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Really great advice. Much appreciated.
In the event that I need to pull out the booster, I've read mixed reviews on doing it with the dash in place. I JUST did the heater core right before this happened and i'm not exactly thrilled about the possibility of pulling the dash again. However, it's not clear exactly what it's like to do it without pulling the dash.
Opinions? |
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