That Damn Brake Warning Light!!!!

[Mark Howard]

O.k. guys....I have renewed everything in the braking system on my teener: new rotors, 19mm MC, new pads, rebuilt the calipers, new ss flex lines, several new hard lines, etc, etc. I have bled this SOB to death....I get pretty good pedal pressure, but not really any better than before I did the MC upgrade. Braking is so-so, not near as good as my 911.

Problem is that the brake warning light flashes indicating a pressure failure. Thinking I left the parking brake on, I raise and lower it, the light stops flashing for a few moments, and starts flashing again.

Thinking I have air in the lines or prop value, I have really beld this sucker to death, easily 50 times per wheel and 3 quarts of super blue through the system! My wife is really getting pissed (mainly because she is 7 months pregnant and i have her pumping the pedal!)

What else can it be?

[kellzey]

Common issue with people rebuilding their brake systems.

Remove the gravel guard underneath the car.

There should be a small button on the master cylinder that needs to be reset.

This button sets itself when there is low brake pressure. So after you blead the brakes and get the system "pressurized", you need to reset that little button.

There might be a small rubber dust boot on it.

The first time I did this I just fiddle around the cylinder and pressed until I heard a "click" sound.

Good luck!

[John Rogers]

If you are one of the "lucky" ones that do not have the reset button on the m/c switch, then there are two possibilities: replace the switch with another one or unhook the warning light and go without it. Both our 914s have the warning light unhooked and have had no problems. DD will probaly say "don't do that, etc" but I don't really need a light to tell me what the brakes are doing??? Good luck.

[gint]

This is one of DD's favorite pics.

See that little nub? If you have a switch on your MC, that nub will be "popped out". Just push it back in. I had the same problem after rebuilding my brake system. That's why I have the picture. ;-)

[jackmech]

I had this same problem. I don't know why everyone talks about the reset switch. It seems like most people don't have that version. Anyway, I had luck with pulling off the two wires and switching their locations. Theoretically this shouldn't make a difference, but it sured my problem. Maybe it'll do the same for you.

[Joe Ricard]

If you want 911 braking quality in your 914 you need 911 brakes. There is no substitute for more pad friction area.
At the risk of starting a Holy war AGAIN. the 19MM M/C did absolutely nothing to improve braking on my car. My right leg did get tired however trying to build the same pressure at the pads.
I only got better braking with the BMW calipers after the pads were bedded in . I have been testing and fiddling with the proportioning valve increasing the rear pressure. so far shorter stops and don't lock before the fronts. Anymore braking power on my car and I will have to get bigger stickier tires to take advantage of it.

[unclerichy]

Gotta agree with Joe. I "upgraded" to the 19mm MC and ss braided flex lines and saw no difference.

[Mark Howard]

No dice on the reset button. Th 911 MC doesn't have one. The old MC did have one, but I really don't feel like breaking the system open again to put that button in. I didn't expect 911 braking power, but I did expect better than it was, and it is alittle better. I agree with Joe, the 19mm upgrade has done nothing for my braking power.

Guess I will just disconnect the switch. But, I have to ask, IF the warning light is coming on, and IF I have no air in the lines and have done everything I can think of to ensure proper braking, and the car is stopping within normal limits, could I experience some sort of brake failure and the car be dangerous to drive?

[Mark Howard]

Update:

Okay guys, I disconnected the wire from the master cylinder. Went for a drive, brake warning light still flashes. Guess that rules out loss of pressure in the braking system.

Now it appears to be an electrical problem. I have the Current Flow Diagram from PP printed and taped together. As I trace the electrical system for the brake warning light, I see two switches, F6 (Brake warning switch), F9 (Parking brake switch) and J1 (Hazard /Turn signal flasher), K7 is the indicator lamp in the warning light. I assume that F6 in on the MC and F9 is on the brake handle.

Any advice on how to further diagnose this problem?

[Dave at Pelican Parts]

The light goes on when either switch (master cylinder or handbrake handle) shorts its input wire to ground. Sounds like your handbrake handle switch may be bad, or the wire to it may be broken or shorting itself to ground.

Having it stop for a moment when you lower the handbrake handle is another clue of that.

--DD

[Kenny Powell]

By jove, Dave I think you've got it!
I had that very thing happen in my car a couple years ago.

[Mark Howard]

I just put a new switch in about a year ago....I'll trouble shoot the switch and see.

Will post with results.