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

Reply to
Trocilan
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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

Reply to
maxpower

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.

Reply to
Steven Stone

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')

Reply to
Bill Putney

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.

Reply to
Trocilan

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')

Reply to
Bill Putney

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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.

Reply to
Trocilan

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

Trocilan wrote:

Reply to
philthy

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