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How to test for a bad master cylinder? #302926
04/29/09 10:53 AM
04/29/09 10:53 AM
Joined: Apr 2009
Posts: 9
Dallas, TX
Hubbs Offline OP
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Hubbs  Offline OP
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Joined: Apr 2009
Posts: 9
Dallas, TX
Hey guys, I'm officially a newbeee, but I've been around for a while. I've been away from the boards for quite some time, and some might remember me as "Chubs".

Here's the question:
I jumped into my Challenger the other day to take it out on its monthly maintenance drive and the brake pedal pushed striaght to the floor. Pumping it does nothing.

Fluid is full and there are no obvious leaks (no puddles by any of the wheels, etc.).

Based on this, I'm betting master cylinder, but I can't remember the best way to test it. Can I get some ideas?

Thanks!

I'll go update my profile now...

Last edited by Hubbs; 04/29/09 11:02 AM.

I used to be "Chubs". Sorry I've been away for so long! I got married and am now "Hubbs"! Garage: 1970 Dodge Challenger 440/4sp 2013 Dodge Charger SRT-8 2014 Ram 1500 2015 SRT Challenger Hellcat (on order)
Re: How to test for a bad master cylinder? [Re: Hubbs] #302927
04/29/09 11:41 AM
04/29/09 11:41 AM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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RapidRobert Offline
Circle Track
RapidRobert  Offline
Circle Track
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
Quote:

I've been away from the boards for quite some time, and some might remember me as "Chubs". Thanks!


A M/C should(A) hold LIGHT foot pressure for ~15 seconds & (B)pressure when you stomp on it. Basic test is to cap both ports with $5 worth of brass plugs from your parts store & a good(& properly bled) M/C will have a rock hard pedal with virtually no travel. With that being said I would bleed it on the car with the kit that has the 2 short rubber lines then cap it( w brass plugs) & if good, hook your hard lines up & bleed out the wheels. If you bleed the M/C then hookup the lines & bleed the wheels without capping the M/C to check it & it's bad you'll have to R&R it then bleed the wheels all over again . Do ya feel lucky


live every 24 hour block of time like it's your last day on earth
Re: How to test for a bad master cylinder? [Re: Hubbs] #302928
04/29/09 11:47 AM
04/29/09 11:47 AM
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
Challenger 1 Offline
Too Many Posts
Challenger 1  Offline
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
You need a new MC for sure. Also need to flush out the old brake fluid while your at it. Good luck.

Re: How to test for a bad master cylinder? [Re: Hubbs] #302929
04/29/09 02:24 PM
04/29/09 02:24 PM
Joined: Apr 2009
Posts: 9
Dallas, TX
Hubbs Offline OP
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Hubbs  Offline OP
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Joined: Apr 2009
Posts: 9
Dallas, TX
Thanks - that's exactly what I was looking for.

What bothers me is the MC is only about 4 years old (probably a whole 5K miles on it). It's a MP aluminum model and the brake fluid was flushed at that time, so there's no excuse other than simply being poor quality MC I guess.

Thanks again - I've already broken open the system to install an adjustable proportioning valve while I'm at it, so it's no biggie to bench bleed the MC at the same time.

I also just bought a nice new vacuum bleeder system that uses shop air to create the vacuum. Can't wait to see how it does!



I used to be "Chubs". Sorry I've been away for so long! I got married and am now "Hubbs"! Garage: 1970 Dodge Challenger 440/4sp 2013 Dodge Charger SRT-8 2014 Ram 1500 2015 SRT Challenger Hellcat (on order)
Re: How to test for a bad master cylinder? [Re: Hubbs] #302930
04/29/09 04:16 PM
04/29/09 04:16 PM
Joined: Sep 2005
Posts: 12,481
Chino Valley
RodStRace Offline
I Live Here
RodStRace  Offline
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Posts: 12,481
Chino Valley
don't forget to check under the dash for any fluid. Clean it up or you will have rust...

Re: How to test for a bad master cylinder? [Re: RodStRace] #302931
04/30/09 09:13 AM
04/30/09 09:13 AM
Joined: Apr 2009
Posts: 9
Dallas, TX
Hubbs Offline OP
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Hubbs  Offline OP
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Joined: Apr 2009
Posts: 9
Dallas, TX
Good point - thanks!


I used to be "Chubs". Sorry I've been away for so long! I got married and am now "Hubbs"! Garage: 1970 Dodge Challenger 440/4sp 2013 Dodge Charger SRT-8 2014 Ram 1500 2015 SRT Challenger Hellcat (on order)






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