pbura
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| posted on 10/8/05 at 02:06 PM |
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Contaminated brake fluid
I'm considering a car for the family beater fleet. Haven't seen it in person yet, but from the sound of things the brake fluid was
contaminated. The guy replaced a lot of parts, but was apparently not thorough and the brakes still lock up.
I think the car will be OK if I do the following:
Replace MC (it comes with a new one in the box)
Replace wheel cylinders
Replace flex hoses
Replace proportioning valve
Rebuild calipers
Flush all steel brake lines with alcohol and let them dry for a day
Am I missing anything? Anyone have a good method for flushing the brake lines?
Pete
Pete
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britishtrident
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| posted on 10/8/05 at 02:18 PM |
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Not sure by what you mean by "the brakes still lock up", brake shoes with oil or brake fluid will make the brakes grab or pull to one side
but not contaminated fluid.
What exactly are the symptoms ?
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pbura
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| posted on 10/8/05 at 02:30 PM |
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Over time, excess pressure builds up in the system, causing the brakes to bind and eventually lock up.
Should have mentioned that the first thing I'd do would be to check the servo and mechanical linkages. Contamination would be a worst case.
Sure would be nice if a blast of WD40 on the pushrod did the trick!
Pete
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Mike S
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| posted on 10/8/05 at 03:04 PM |
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Sound to me like the master cylinder is not returning far enough to let the pressure back to the fluid reservoir.
I would check that the pedel is returning correctly, and overhaul the master cylinder.
Cheers
Mike
There are more horses' asses in this world than there are horses
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pbura
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| posted on 10/8/05 at 03:21 PM |
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Could be the master cylinder, too. I thought the owner had changed it out once already, but he hasn't. He put in new calipers, though
(ouch).
I understand that in a contamination case, the seals in the M/C will swell, preventing relief of pressure. The way the guy has attacked the problem
(flushing his system and replacing hoses) makes me think he may know of contamination but isn't talking about it.
Pete
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nick205
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| posted on 10/8/05 at 03:48 PM |
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Pete,
What car is it - must be something interesting if you're considering that much potential work/expense on it?
Nick
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pbura
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| posted on 10/8/05 at 04:00 PM |
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quote:
Originally posted by nick205
Pete,
What car is it - must be something interesting if you're considering that much potential work/expense on it?
Nick
LOL
A fifteen-year-old Mazda 626. I have one already and love it.
Pete
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britishtrident
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| posted on 10/8/05 at 04:56 PM |
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Yes Mastercylinder -- Could be just a badly fitted brake light switch at the pedal stop but most likely it is the adjustment of brake servo push rod
-- undo the two nuts that hold the master cylinder to the servo pull back the cylinder a couple of inches and you will see the end of the push rod
turn which usually has an 8mm hex nut and lock nut it for adjustment it back a bit until it has a few mm clearance between the end and the master
cylinder piston.
A lot of people twiddle with these think it will reduce movent at the pedal.
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The Shootist
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 posted on 10/8/05 at 05:38 PM |
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Another possibility, often overlooked...
A flex-line can have the inner liner collapse and act as a one-way valve. The brakes will release after sitting, but wll gradually tighten up after a
few stops.
Had a front wheel on a Chevelle do just this, and tried everything until an old-timer mentioned the flex-line. After replacement I cut the flex in the
midddle and sure enough, it was collapsed just as promissed.
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britishtrident
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| posted on 10/8/05 at 05:57 PM |
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quote:
Originally posted by The Shootist
A flex-line can have the inner liner collapse and act as a one-way valve. The brakes will release after sitting, but wll gradually tighten up after a
few stops.
Had a front wheel on a Chevelle do just this, and tried everything until an old-timer mentioned the flex-line. After replacement I cut the flex in the
midddle and sure enough, it was collapsed just as promissed.
I was wondering how long it would be before somebody trotted that old myth out.
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pbura
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| posted on 10/8/05 at 11:42 PM |
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quote:
Originally posted by britishtrident
quote:
Originally posted by The Shootist
A flex-line can have the inner liner collapse and act as a one-way valve.
I was wondering how long it would be before somebody trotted that old myth out.
Pretty rough, BT!   If nylon panties can bunch, why not brake hose? 
Thanks for the suggestions, guys. I'll try to use my head before chucking a lot of money at the problem 
Pete
Pete
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Rorty
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| posted on 11/8/05 at 07:04 AM |
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quote:
Originally posted by pbura
If nylon panties can bunch, why not brake hose?
And just how do you know about Nylon panties bunching?
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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NS Dev
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| posted on 11/8/05 at 08:24 AM |
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another thing that can happen (it did on my old manta) is the vacuum control valve on the servo can fail, causing the inlet manifold vacuum to be
permanently applied to the servo, which then tends to pull the brakes on. Seems to do it intermittently when it happens.
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pbura
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| posted on 11/8/05 at 11:09 AM |
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quote:
Originally posted by Rorty
quote:
Originally posted by pbura
If nylon panties can bunch, why not brake hose?
And just how do you know about Nylon panties bunching?
That's what they do every time I wear a rubber suit!
Pete
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