Brake Problem -- 99 Chrysler LHS -- Please Help!!

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

 

If the master cylinder was contaminated with an oil base substance such as
motor oil it will cause the seals to swell up in the system and will cause
the brakes to seize up. The first clue would be the master cylinder cap
inside seal. If the seals are swelled up, the system was contaminated. If
the vehicle was in an accident the firewall could be bent and causing the
pushrod in the master cylinder to apply pressure causing the brakes to
seize. When the problem occurs, loosen up the master cylinder as the wheels
are off the ground and see if the wheels free spin.

Glenn Beasley
Chrysler Tech

 

Were the replacement calipers rebuilt or new ?
I had some unusual problems with caliper lockup when the piston seal
(in this case a square rubber o ring) hardened up from age.

I also had the same problem with some rebuildt units.

 

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 accumulated in the booster is freezing and interferring with
proper operation (internal valving). It is a known fact that water does
accumulate 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 accumulates 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 vaccum 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
accumulation 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')

 

Thanks very much for the replies. I will show them to the mechanic in
a couple
of days.

I presume the calipers were new...I was *charged* for new parts...

If you (Mr. Beasley) mean the cap on the brake fluid reservoir, I
looked there
and its seals were not swollen. If you mean something else, the
mechanic
will know what you are talking about.

NEW SYMPTOM:
On a whim, I started the car, checked to see that the brakes were
*not* siezed
up, then let the car warm up without pressing the pedal. Sure enough,
half-hour
later, the brakes were seized up even though I had never touched the
brake
pedal. The outside temperature was well above freezing, maybe 40-50
F.

Thanks again for your help. I will give all replies to the mechanic
when I
take the car back.

 

I'm realizing now that you had two opposite situations (I only caught
the "no brakes" situation when I replied the first time): One in which
the brakes were seized up - I now take that to mean that at least one
wheel was hard to turn (brakes applied), and the other situation in
which the brakes would not apply. There may or may not be two root
causes, but it is possible that the booster could have caused one or
both (due to internal valving problem(s)). If you get the "brakes
seized up" problem again, see if you can turn that problem off by
disconnecting and plugging the vacuum hose to the booster - if you turn
the problem on and off by connecting and disconnecting the vacuum hose,
then it definitely is the booster. BE AWARE THAT YOU WILL ESSENTIALLY
HAVE NO BRAKES WHEN THE VACUUM HOSE IS DISCONNECTED - I.E., DO NOT DRIVE
THE CAR WITH THE VACUUM HOSE DISCONNECTED.

Also, maybe it is possible there is water in the brake lines themselves
(expanding at times, blocking pressure at other times). That's a WAG
for a possibility. But I've got to think either that or booster problem.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

---------------

Success! (I hope...It has been less than 24 hrs.) I had the brake
lines flushed and refilled with new fluid and the problem has not
recurred so far. The tech did note that, while he was pressure-
bleeding the rear brakes, the front brakes seized up a little. He
thought the proportioning valves might need replacement. Also, he
recommended I bring the car back to test the ABS. I'll certainly do
so if the problem comes back but, for now, I'm just going to drive!
The brakes seem to be working fine now.

Thanks for all your help!

B.

 

if oil was introduced into the master cylinder
the pedal would become hard to push once then after the seals let loose then
the pedal could be pushed to the floor and the brakes would not work very
good almost like a bad master cyl.but would yoy would still feel some
pressure
i have had the headaches of figuring this out 3 times on cars in the last 2
months