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Brake press warning

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Old 10-10-2012, 09:45 PM
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sndrunr1
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Default Brake press warning

When I applied the brakes at red light, the brake pedal felt a little soft & went down further than usual, but I stopped fine. The brake pr light and the main warning light started flashing. I can't get these reset by pushing reset button. I still have good brakes, but lights still flashing. I checked rear brake lights in garage when I got home, so I'm thinking the pressure switches are working, unless 1 is for brakelight and other is my problem. Any ideas? Thanks, Gary
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Old 10-10-2012, 09:51 PM
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Barry Chan
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You won't get much help if you don't have the MY of your car
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Old 10-10-2012, 09:51 PM
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That warning isnt about tail lights.

If your pedal fell, you probably have lost your master cylinder..or a line is broken..look under the car for leaks perhaps?
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Old 10-10-2012, 09:55 PM
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sndrunr1
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My car is 1980 928S Euro. I have no leaks, & fluid resevoir is still full. Maybe master bypassed or something. Is there another pressure switch, or what does the light sense?
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Old 10-10-2012, 11:19 PM
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See this link---also a 1980 model: https://rennlist.com/forums/928-foru...ht-1980-a.html

Rennlisters came to my rescue a few years ago!
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Old 10-12-2012, 12:44 AM
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I got flashing lights reset by disconnecting battery, must be a latching relay in warning controller somewhere? I re-bled brakes with pressure bleeder even though I still had good brakes. The master cylinder may be trying to bypass or something to give the fuzzy feeling when brakes are applied. Will address this 1st, as I think this is the root problem, will change switches also because I don't want to end up in store like other Porsche driver on Leno did. Thanks, Gary
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Old 10-12-2012, 01:36 AM
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If both brake light circuits dont fire together (which produces the error msg you see) it means either one of the switches is faulty, OR there is a pressure difference in the two circuits . This last can be caused by either a leak, OR a seal failure inside the M/cyl. If you felt a change in the pedal , but no signs of leaks, its very likely to be the m/cyl, but not 100% IMHO. Note that new M/cyl come with switches fitted, but not the reservoir. How old is that M/cyl now? When was the fluid last flushed through? Did mine last year.
jp 83 Euro S AT 54k.
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Old 10-12-2012, 02:28 AM
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If the master cylinder is 15 + years old , then there is a 99% chance that its just the M / Cylinder & what's nice is the" pre" 86 master cylinders are not expensive ( not post 86 )
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Old 10-12-2012, 04:01 AM
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One thing you can try is with the motor running stand on the pedal hard. If it slowly sinks at all you have a leak (fluid loss) or MasterCylinder problem (internal bypass or seal issue)..

If you notice any change in brake pedal feel, including issues like the pedal seeming to initally be 'low' however it 'raises itself' once you pump it, or slowly sinking to the floor, you should inspect and/or replace the MC.

Brakes are probably the most important control element (other than steering) that you have and if you lose them / bad...
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Old 10-12-2012, 11:40 AM
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I had the same problem.

Apparently those switches very very sensitive to even the slightest loss of pressure. I had no visible leak, no loss of fluid to be found anywhere. The brake pedal would become just a bit spongy if I was stopped on unlevel pavement. Replaced the M/C and switches and good to go.
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Old 10-13-2012, 12:46 AM
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[QUOTE=dcrasta;9912519]One thing you can try is with the motor running stand on the pedal hard. If it slowly sinks at all you have a leak (fluid loss) or MasterCylinder problem (internal bypass or seal issue)..

Is it still safe to drive? Will you loose the braking all of a sudden?
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Old 10-13-2012, 12:58 PM
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The resident experts could explain in more detail, but I understand the braking system has redundancy making a loss of braking very unlikely.
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