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Brake Wear Light And No Parking Break Light

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Changed out my '99s coolant tank over the weekend. On my 1st test drive the Brake Wear light comes on. Stayed on for about 5 minutes and haven't seen it since. When the coolant tank failed there was quite a bit of coolant that emitted into the trunk area and drained out around the rear right wheel...

Does anyone know how the break wear sensors work? Is it based on caliper travel or ability to 'grab'? Could coolant on the right rear rotor have caused the light to come on temporarily until the residue burned off? Have braked hard trying to duplicate the sensor reading to no avail...

Also, just this afternoon when stopped at a long light I attempted to open my top. Nothing. I looked down to see that the Emergency Brake light would not come on. I reset the brake a number of times with no luck. The brake is working, I tested it on a hill. The light is illuminated on start-up so the bulb's OK. Any thoughts?

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The sensor is a simple loop of wire covered by black plastic. When the friction material becomes thinner and the pads move towards the rotor the rotor grinds away at the wire until you have an open circuit and the light goes on. Some say that if a sensor is worn and gets wet the light will go on.

Start the car and then pull up on the hand brake lever. If the light does not come on then you have a bad hand brake switch - a common problem on older cars and there is a new design switch. If pumping the lever does not get the light to come on then it is time to replace the switch.

I cannot think of how either things are related to the tank replacement.

This is the sensor.


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Pumping the handle didn't work this morning so I'll pick up a new sensor and replace. I'm sure there's instructions buried somewhere in here. Should I pull the wheels to see if it is time for new pads (and sensors)? Or should I right off the one time illumination to a faulty sensor and wait until I get a steady light?


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To check for a bad brake wear senson there is a cheap and easy way.

Take the sensor that you think is bad and cut off the portion that fits into the brake pad. This will give you 2 small wire ends. Strip both wires and twist together and tape. Plug it back into the receptacle on the strut. If the brake wear sensor light stays off then you know it is a bad sensor. The sensors are just a complete circuit until the pads wear to allow the wire to be broken...interrupted circuit triggers the brake wear sensor. I got tired of mine so I just permanently wired all of them as above so the light stays off. I check and change pads often anyway for track purposes so the light was just an annoyance anyway. :D

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Thanks for the input guys...

Installed the new Parking Brake switch (996.613.112.01=$5.64) this morning. Used the 'Remove Handbrake' section (under Maintenance) from www.986faq.com to remove center console.

Directions worked like a charm, a couple of notes though...

1) When removing the console make sure you disconnect the alarm wires to the storage compartment. It's a push-on type connector.

2) There is one 20 Torx screw that is shorter and a different thread type than the others. If your going fast you may not know where it came from when reinstalling. It's from the back floor of the storage compartment.

3) The Torx screws underneath the ash tray continue to spin even when tight. The fitting is similar to a hollow wall anchor in that the 'wing' spread on the far side securing the piece in place.

4) I did not have to remove the shifter. After pulling up the boot I just translated it so the 'tongue' pointed to the ceiling, the console cleared easily.

Thanks again for all the help, I'll take a look at the brakes on Sunday.

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  • 2 weeks later...

Took a look at the brakes today while replacing the spark plugs... Although I continue to get an off and on (mostly on) brake wear light, the pad thickness looks OK all around. Compared to Tool Pants picture above I have about 2x as much pad left (textar). The 'pad' side is definitely thicker than the 'base' side.

Is there a standard measured thickness when pads must be changed?

I don't do a lot of heavy braking...


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You have an intermittent short, does it short depending on acceleration or maybe turning right or left.

It seems the wire is grounding somewhere.

Maybe Tool pants can tell you if the parking brake system lighting/wiring is on the same circuit as the brake fault system.

It seems the wire is swinging back and forth.

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  • 1 year later...
Tool Pants,

My "Brake Wear" light just lit a few minutes ago.  How soon do I have to replace the pads?  Will I be able to drive the car for another week?  Thanks

Unless you are going to the track this weekend, another week should be fine. The pads have some life aftger the sensor wires start grinding down.

BTW- double check that it is the "brake wear" sensor rather than the "brake fluid" sensor. This can be done by looking at the brake fluid level in the front trunk. The guage is on the side of a plastic tank. My brake fluid went low before my stock pads wore out.

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Thanks for the info. On my last oil change, the tech told me that I will have to replace the pads soon but don't know how soon. If I bring them the frot and rear sets, purchased from the internet for ~$650, they will have them installed for $400 (for 4 hours). Does this labor cost seem reasonable?

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I had a similar problem with a 98 and it was the result a break in the sensor wire at the point it attaches to the plug (white plastic on the 98) that connects to the frame. This was found by moving the sensor wires on each wheel until the problem was identified.

The problem was corrected by soldering the wire back on the plug. This required some work on the plug to get enough wire visible on the plug.

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Thanks for the info.  On my last oil change, the tech told me that I will have to replace the pads soon but don't know how soon.  If I bring them the frot and rear sets, purchased from the internet for ~$650, they will have them installed for $400 (for 4 hours).  Does this labor cost seem reasonable?

Rear brake pads generally last much long than front pads - you are unlikely to need to replace front and rear unless you are planning to go to pagid orange or some other racing/non-stock brake pad.

Changing the brake pads take about 15 minutes per wheel longer than changing the tires. Once you have the wheel off, the first pads might take 30 minutes because it is hard to figure out how to remove the brake wear sensors without breaking them and because it is the first set. The subsequent pads take about 10 minutes each. Depending on how long it takes you to jack a car and locate your Torque wrench, this is about a 3 hour job in a home garage.

My first brake pad change was front only and took 3-4 hours but this included installing speedbleeders on all 4 wheels, totally replacing the brake fluid, and bleeding the brakes. It was the first time I had worked on brakes in about 30 years and is basically a 'piece of cake' to do right.

A big time saver is to jack the rear jack point until the front wheel lifts and do one side at a time.

This is a great link if you are thinking of doing it yourself http://www.bombaydigital.com/boxster/proje...es/change_pads/

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  • 4 months later...

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