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Old 09-08-2007, 10:15 AM
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Join Date: Apr 2004
Posts: 46
Please help with 560 brake problem

I have a 89 560sl 24000k. driving home last night i lost my brakes,peddle down to the floor nothing happening.Luckly i was able to safely get to the shoulder. I turned my car off while waiting for help.I turned the car back on after 10min and the brakes were fine. I was able to continue home without a problem.What do u think this is? btw my abs light has been on for a few months,my mechanic said it would not affect my regular brakes. Thank you.
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Old 09-08-2007, 10:21 AM
t walgamuth's Avatar
Join Date: Apr 2005
Location: Lafayette Indiana
Posts: 34,523
It might be low on fluid. Of course if it is that also signifies a leak in the system which must be repaired too.

Tom W
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.
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Old 09-08-2007, 10:31 AM
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Join Date: Apr 2004
Posts: 46
thanks Tom, I check and the fluid seems fine.
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Old 09-08-2007, 10:53 AM
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Join Date: Dec 2004
Location: Nashua, NH
Posts: 3,956
two words...master cylinder. MCs can fail when they get warm and after cooling off work again...if you have no record of having replaced it that would be my advice...classic symptoms of a leaky MC and it will happen again. Next time you might not be so lucky.

The only other thing I can think of is if you had been using the brakes a lot prior to the failure you may have boiled the fluid due to overheating them. That would be like going down a 10 miles incline riding the brakes the whole way...was this the case? If so you probably want to have the fluid flushed out.
Marty D.

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Old 09-08-2007, 11:19 AM
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Join Date: Apr 2004
Posts: 46
thanks nhdoc,it was a very hot day and i was in heavy stop and go traffic.assuming it is the MC, what should i expect to pay for that repair?
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Old 09-08-2007, 12:40 PM
Join Date: Oct 2004
Location: NC
Posts: 2,995
As far as I know, there is nothing else besides the master cylinder that can cause this without showing up as a leak somewhere, except for maybe the ABS unit itself. I'm hoping someone will educate me on this here. That being said coupled with your ABS warning light points to the ABS module.

However master cyclinders can not work one day and then work fine the next therefore if this happened to me I would replace the master cylinder reguardless of any subsequent test performance or any other repair work performed. You have the right milage and the right age. Just do it. This should be doable by any indy for under $300.00 or any dealer for under $500.00 or by yourself for about $150.00. It's about 1 hour of work.

Also the best way to test the master cylinder for this problem is to step on it and hold a steady light pressure. Ususally (but not always) master cylinders with this kind of problem will slowly do down to the floor under light pressure load, but they will work fine when you stomp on it. If yours fails this test you will feel very good about not wasting money to replace you master cylinder. If it passes this test just bite the bullet and replace it anyway.

Please note this does not mean to disreagaurd the ABS unit. I just dont know enough to comment on it. And of course you should look for evidence of leaks everywhere.

John Roncallo
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Old 09-08-2007, 02:11 PM
speace's Avatar
Join Date: Jan 2003
Location: Atlanta, GA
Posts: 370
Since it was a hot day there is another scenario that has actually happened to me in my 400E.

My brakes went out, pedal to the floor on a hot day after driving in heavy stop and go traffic. They worked just fine after cooling down. The problem was that my calipers overheated and boiled the brake fluid.

Once the fluid in the calipers boils, the bubbles compress as you press the pedal thus preventing any hydraulic action. (No leaks.) Once it cools down, the bubbles are re-absorbed by the brake fluid and everything is normal again.

Two factors were involved:

First, I had those %$# Dust Shields on my front wheels to protect the car from brake pad dust. (I now consider them UNSAFE because they restrict the airflow needed to cool the brakes!)

Second, if the brake fluid has not been changed in a while there may be a high moisture content in the brake fluid as is natural over time. High moisture content will lower the boilng point of the brake fluid. My brake fluid was due to be changed...

Since changing the brake fluid and removing the "Kleen Wheels" devices I have not seen the problem again! That was SEVERAL years ago. I still have the original master cylinder.

My experience with failing master cylinders is that you can press the pedal and it will surprise you by going to the floor, yet one or two more pushes later they are fine. If you ignore it, the problem will come back with increasing frequency until it hapens so often you don't feel safe driving the car.

You can certainly go ahead and change the master cylinder if you like on general principle for peace of mind, but my bet is on boiling brake fluid!
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Last edited by speace; 09-08-2007 at 02:16 PM.
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