Trocilan wrote:
> Car has the following symptoms:
>
> After I drive the car about 12 miles, the brakes slowly sieze up. The
> longer I drive, the tighter they get and the harder the pedal
> becomes. After the car cools off overnight, the pressure gets
> relieved and the brakes loosen again. The front brakes are more
> severely affected than the rear ones (you can tell by trying to spin
> the wheels).
>
> I replaced the front calipers to no avail. The brake hoses were ruled
> out as the cause of the problem. The Chrysler dealer's mechanics
> didn't feel that the master cylinder or the vacuum booster were
> involved because the problem wouldn't come and go as it does.
>
> The problem is closely connected with temperature because, one very
> cold day, the brakes froze open. Could only apply them the next day
> when it was warmer.
>
> Could the ABS (anti-lock braking system) or TRAC (traction control
> system) be the cause of the problem? How can they (or the master
> cylinder or booster, for that matter) be tested?
>
> Coincidentally, the car started losing engine oil at about the same
> time the brake problem started. Probably no connection.
>
> If anyone has any idea what is going on, please help! This could get
> expensive....
>
> JB
We've recently seen multiple posts on the 300M Club forums of this kind
of problem. Onset was with freezing weather. I'm convinced that it
definitely has to do with the cold, and is one of two things:
(1) Water ac***ulated in the booster is freezing and interferring with
proper operation (internal valving). It is a known fact that water does
ac***ulate from condensation inside the booster (every time you use the
brakes, it "breathes" in some outside air - the moisture in the air
condenses out and ac***ulates a significant amount over time - anyone
who has replaced a booster can attest to this).
(2) Wear in the booster valving causes the sealing of the parts against
each other to be marginal - and temperature dependent.
The more likely cause is (1). You could probably pull off water with a
syringe and plastic tube thru the vac*** hole after removing the check
valvae, but I don't think there is any way to remove water out of the
rear chamber. Probably the best solution is to replace the booster with
a rebuilt one (around $85 at most auto parts stores - NAPA uses the same
rebuilder as everyone else, but charge around $105 for theres, so in
this case, migh tas well get it from somewhere else).
BTW - booster failure from wear that manifests itself in warmer weather
*can* in fact be intermittent. I experienced it myself on my '99
Concorde (mechanically same car as the LHS) - replaced booster, problem
gone. But I think your problem is temperature related due to the
ac***ulation and freezing of water.
Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')
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