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  #1  
Old 04-17-2008, 09:27 AM
Jimmy Joe's Avatar
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Brake fluid quantity for flush? Pedal fade?

Hi folks,
Coming down the mountain my brake pedal fades to nothing if I hold her down a couple times (kinda more of a multiple application thing, not so much if I just apply it once, i'm guessing...); reading the archives here I suspect water in the fluid. Maybe bad master cylinder too, but I am not sure how to differentiate the two issues.

So I figure, time to change the fluid anyway, it has been 4 or 5 years, first; then if problem is not solved, move on to the master.

Or maybe you folks think I am wasting my time doing the flush prior to the master?

Anyone have an idea of how much brake fluid she is going to gobble up with a complete flush?

Thanks!
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  #2  
Old 04-17-2008, 10:08 AM
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Quote:
Originally Posted by Jimmy Joe View Post
Hi folks,
Coming down the mountain my brake pedal fades to nothing if I hold her down a couple times (kinda more of a multiple application thing, not so much if I just apply it once, i'm guessing...); reading the archives here I suspect water in the fluid. Maybe bad master cylinder too, but I am not sure how to differentiate the two issues.

So I figure, time to change the fluid anyway, it has been 4 or 5 years, first; then if problem is not solved, move on to the master.

Or maybe you folks think I am wasting my time doing the flush prior to the master?

Anyone have an idea of how much brake fluid she is going to gobble up with a complete flush?

Thanks!
Get 2 liters. You'll use less.

Are there any leaks? Did you check where the master cylinder and booster meet?
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  #3  
Old 04-17-2008, 10:24 AM
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Quote:
Originally Posted by Jimmy Joe View Post
Hi folks,
Coming down the mountain my brake pedal fades to nothing if I hold her down a couple times (kinda more of a multiple application thing, not so much if I just apply it once, i'm guessing...); reading the archives here I suspect water in the fluid. Maybe bad master cylinder too, but I am not sure how to differentiate the two issues.

Water in the brake fluid will cause a noticable problem only when the brakes get very hot and cause the water to boil. Once the fluid cools, the brakes will operate normally.
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Old 04-17-2008, 10:48 AM
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Ya, I think the brakes were getting hot, not so you could smell them or anything, but warm from going down the hill. I wonder just how hot they would have to be for a fluid situation...in any event, I love my car and this is simple stuff, so I will do it anyway. I just would rather know if my master is bad b4 so I don't bleed twice...

Any simple test to verify master cylinder function?

No leaks, no fluid loss.
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Old 04-17-2008, 10:51 AM
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Originally Posted by Jimmy Joe View Post
Any simple test to verify master cylinder function?
Will constant pressure on the brake pedal eventually send the pedal to the floor?

An internal leak in the m/c will not necessarily result in fluid loss. The fluid just leaks to the back side of the piston.
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Old 04-17-2008, 10:55 AM
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Originally Posted by tangofox007 View Post
Will constant pressure on the brake pedal eventually send the pedal to the floor?
Hmm, not really, seems only if I apply then release a couple times. If I brake once, then maintain constant pressure, it seems to hold. The second time I applied it seemed to fade. Granted, I was on a big hill and didn't fool around with it too much...
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Old 04-17-2008, 12:59 PM
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Its overdue for a flush. 2 year span is correct. I would also verify the front rotors are not too thin. Usually after the third to forth pad replacement the rotors are worn too thin. Thin rotors wont dissapate heat well and could contribute to fade. Also, desending a hill you should manually shift to 2nd. Less strain on your brakes.
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Old 04-17-2008, 02:30 PM
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it could also be your booster. at a stop sign, push down on the brakes and let go, then push again and let go, how many times can you do it and still hold the car at the stop sign?
brake fade is where you are pushing on the brakes and they work for a few times, then you still have power assist, but the pedal fails to actuate the brakes. water in the lines will do this quickly going down a long hill.
if it's the MC the pedal is going to go the floor... usually.
first step is flush all the fluid out.
somebody on here uses blue fluid for the first flush, then gold fluid the next 2 year flush, then back to the blue fluid then back... makes it easier for him to know if all the fluid is out.
make sense to me... now where do you buy this blue fluid?
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Old 04-17-2008, 03:23 PM
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Last year I did the brake fluid on my W114...

I had a new can, 1.5 litres....

It was Only Just enough!
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