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Discussion Starter · #1 · (Edited)
Master Cylinder Problem?

I am a lazy azz and waited until 118k to flush my brake fluid (after changing to GA front calipers). Well, I believe I may have put my master cylinder out of business. I push the brake pedal down, and it feels pretty normal, but if you hold it down, it will slowly go to the floor. I bled all 4 calipers twice (just to be sure there was no air), and I don't have any massive leaks, so it must be the master cylinder.

So I replaced the master cylinder, expecting all to be fixed. Well, it turns out that it does the same thing. So my question is do you think my master cylinder that I just bought (rebuilt) is bad? Here are my next steps:

1. Put stock calipers back on and re-check. If problem is gone, the calipers are bad.

2. Replace the MC again with another rebuilt one (assuming the one I just purchased was faulty).

Do you guys have any other ideas as to what is causing this? Could it be something in the ABS or TC modules? I properly bled the ABS module, and all 4 calipers in the proper sequence. Oh, and I don't have any leaks either.

Thx!
 

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Jason,


I have a couple of ideas. First, if you have used calipers, i would closely at the area aroung where the hose bolts on. I have seen these calipers be so corroded around that area that the sealing washers won't take. Clean as necessary.
Secondly, I have seen calipers installed on the wrong side of the car. This puts the bleeder on the bottom, which makes bleeding impossible. Third, the brake pads only go in 1 way. If they are backward you can still bolt up the caliper, but may have a fade issue. The pad with the biggest tab on the convex surface is the inboard pad.
Hope this helps.


BIG JEFF
 

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BIG JEFF said:
...if you have used calipers, i would closely at the area aroung where the hose bolts on. I have seen these calipers be so corroded around that area that the sealing washers won't take. Clean as necessary...
Also, if you have re-built calipers, I've seen the rebuilders sand-blast the machined sealing surface at the fitting... idiots...The pebbled surface does not let the washers seal as they would on freshly machined concentric rings...

If they're really bad, you can get leaks there as Jeff mentioned. I've had some so bad I've taken them back to the parts counter and had them bring several out and picked the best one.
 

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Discussion Starter · #7 ·
Thanks for the info, guys. Better late than never. ;)

Anyway, I have it fixed, but I'm still puzzled. I put the stock calipers back on, and the problem was fixed. Then I put the GA calipers on again, and the problem was there, but then I found a small leak on the passenger side. It turned out to be my stock brake line was bad. I replaced it, then there were no leaks. However, the soft pedal feel was still there. I drove it for a couple weeks, then just the other day, out of nowhere, my SVS/ABS/Trac Off lights lit up, and the pedal was firm. After cycling the ignition, the lights went out, and the firmness was still there. I don't know how the hell it fixed itself, but it did! :)
 

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Discussion Starter · #9 ·
I didn't say I was happy. ;) Actually, I'm still looking for insight as to what the problem could have been. Yes, it did fix itself (at least temporarily), but I still have the thought in the back of my head that it will rekindle itself down the road.

So, any other ideas? The calipers are on the correct side (I checked for L and R before installing ;)), and there are absolutely no leaks, and there is no air in the lines.
 

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Make sure your emergency/parking brake works....just in case.
I had a similiar prob with my old '78 malibu, it fixed itself for awhile but it came back twice as bad. I just noticed brake fluid leaking from the brake booster diaphram, and from where the the master cyl. bolts to the booster. Might not be the same for you but, just FWIW.
 

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Discussion Starter · #11 ·
Thanks for the input, Shawn. Yes, my e-brake works, I'm sure to use it every night, just in case I ever need it. :)
 

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I assume you did also bench bleed the master cyclinder before instalation? Otherwise it's impossible to bleed all the air out while it's installed on the car.

Cheers,
 

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Discussion Starter · #13 ·
Yes, I did that as well. Actually, not sure on the GP's, but the 97-98 Regals come with the MC attached to the ABS module, so I bench bled both of those together.
 
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