wierd "brake" problem... suggestions?

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danny burstein - 15 Aug 2006 14:50 GMT

car; 1998 Grand voyager, v-6, 3.0L

Problem: after (very roughly) a half hour of
driving, the brake starts to grab (as if I'd
lightly pressed it) and slow/stop the car.

if I stop and pump the brake pedal a few times, it
releases and lets me go for a few minutes,
then starts up again.

If I then shut off the engine and restart, I
get some more time before it happens again.

(If it's a completely cold startup, I get that
very roughly half hour).

The shop replaced the front brake pads which were
kind of ok, but pretty long in the tooth, and
also a caliper.

Same thing happened.

They're guessing at straws now, and I'd rather
come up with some focused ideas rather than
go through each piece being replaced..

Any suggestions? Thanks

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fireater - 15 Aug 2006 15:44 GMT

> car; 1998 Grand voyager, v-6, 3.0L
>
> Problem: after (very roughly) a half hour of
> driving, the brake starts to grab (as if I'd
> lightly pressed it) and slow/stop the car.

Do you even have to touch the brake pedal for this to start to occur?

if not i would suggest you check for free play between the brake pedal
pushrod and the master cylinder. you should be able to wiggle the pedal
a small amount (up /down) like 1/8 inch before you "feel" the pushrod
contact the master cylinder piston.

if this has no clearance it can hold residual brake pressure on and when
the front calipers warm up the pressures could rise.

or you power brake booster could be faulty. and self applying..
disconnect the vacuum line to it (plug it) go for a drive (CAREFULLY
CAUSE THE BRAKES WILL BE VERY HARD)and see if if they come back on.

> if I stop and pump the brake pedal a few times, it
> releases and lets me go for a few minutes,
[quoted text clipped - 17 lines]
>
> Any suggestions? Thanks

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danny burstein - 15 Aug 2006 15:56 GMT

>> car; 1998 Grand voyager, v-6, 3.0L
>>
>> Problem: after (very roughly) a half hour of
>> driving, the brake starts to grab (as if I'd
>> lightly pressed it) and slow/stop the car.

>Do you even have to touch the brake pedal for this to start to occur?

Nope. I first notice it as my car slows down... (or, if
I've got the cruise control running, I'll see the
RPMs go up or hear the engine laboring).

>if not i would suggest you check for free play between the brake pedal
>pushrod and the master cylinder. you should be able to wiggle the pedal
> a small amount (up /down) like 1/8 inch before you "feel" the pushrod
>contact the master cylinder piston.

>if this has no clearance it can hold residual brake pressure on and when
>the front calipers warm up the pressures could rise.

>or you power brake booster could be faulty. and self applying..
>disconnect the vacuum line to it (plug it) go for a drive (CAREFULLY
>CAUSE THE BRAKES WILL BE VERY HARD)and see if if they come back on.

Signature

_____________________________________________________
Knowledge may be power, but communications is the key
dannyb@panix.com
[to foil spammers, my address has been double rot-13 encoded]

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