LA4Mead

Recently the BRAKE indicator started flickering with a corresponding chime. I'm under the impression the only conditions that it would warn are for the parking brake, low brake fluid level, or low brake fluid pressure. However, there is no loss of brake fluid pressure, the fluid level is OK, and the parking brake fully releases. Yet the light comes on intermittently, flickers irregularly, and the chime activates with it annoyingly.

It seems to be worse when the vehicle is cold (and continues until heat soak) and/or at the same time a high-load switch is turned on (like the headlights or rear/mirror defrosters).

My guess is either a bad parking brake switch (where is it?) the fluid level sender in the master cylinder cap, or brake line pressure sender (again, where is it?).

Has anyone else come across this phenomenon?
How was it dealt with?
Is there another reason the BRAKE indicator is supposed to warn for (is there a hard-wired sensor for other conditions?
Any advice which switch, and it's location?

To avoid confusion, it's not the orange warning for a burned bulb or the ABS warning. It's the indicator that normally comes on while starting or when the parking brake is depressed.

Early '99 RX300 2WD (3/1998)
Thanks for your help!

salimshah

Double check the level again.

There is a float like device in the filler cap. Have an assistant move it up and down with the cap removed (try not to contaminate the thing as it will go back in the master cylinder/reservoir.

A few people have reported problems with the sensor.

Salim

trhs75

Oh, boy, do I remember this problem on my '99. The dealer was completely stumped. The light and chime would go on whenever I would use the turn signals, raise or lower a window, and sometimes spontaneously. The service advisor said he never would have believed me if he hadn't seen it happen with his own two eyes. I thought it would drive me crazy. I checked the brake light switch over the pedal and it was fine. Salim is right about the float device, but apparently there is more than a simple float switch in there -- some kind of chip or something. Anyway, someone on this forum suggested replacing the brake reservoir cap (look for the thread in this forum), and that solved the problem instantly. The part was about $100, but that's what it took. The dealer was still skeptical. Let us know if that does it!

lexina

Your brake pads could be low. replace the pads. especially on our car, the further you let the pads wear out, the boost will get stretched and it will be hard to slide it back into the caliper.

LA4Mead

This was my first assumption. What you are saying does make some sense if there is a sensor to tell the system the pads are worn, other than by fluid level. If so, where might it/they be? I haven't heard of that type of sensor yet.

However, if it's just a matter of brake pads being worn and replacing them will extinguish the warnings, how does the system know? When the pads are worn, the fluid level drops. However my fluid level was nearly full, and I topped it off anyway, but that made no difference.

Use of the brakes does not seem to have anything to do with the warning. It's completely independent of the use of the brakes, so I'm guessing/hoping it's the fluid level cap sender unit... When I can I'll conduct the test Salim, TR, and others wrote about. I wanted to do that anyway.

Before posting I checked other threads, but the results were inconclusive.

I'll report back with what I find out. They aren't new so I may get new brakes sometime soon anyway, but that will have to wait. They seem to have more than enough material.

In the meantime, I appreciate everyone's suggestions, experience, and comments. Go ahead and let me know what you think. Thank you!

LA4Mead

OK, about 5 months ago I topped off the brake fluid, although the level was not low. The "BRAKE" warning indicator and chime did not go away immediately (weird) but gradually over a week or so, and then nothing until yesterday. It came back again, extremely annoyingly on a long trip. As the brake indicator flickers, the chime sounds with each flicker like d-d-d-ding-d-d-d-d-d-ding... on and on. Finally, I stopped to buy some fluid; this time filled it well above the full mark, and moved the float up and down. Now the indicator stays on (which at least the chime isn't dinging with each flicker) so I'd have to say it is in fact the float/sender in the cap.

I thought of replacing the brake pads anyway; that might help only as far as that would result in a higher fluid level, just as adding fluid did, so I'm waiting on that. Sometime soon I'll get a complete brake job and fluid flush because it feels like the rotors need to be turned or replaced, another expense I'm not looking forward to. But there is life left on the pads, and other than the pulsation from the rotors all is OK.

Conclusion: As Salim said, I'm pretty sure the sender in the float mechanism is bad, as it's happened to others.

Does anyone remember the part number (for the early '99 model with the sender in the round cap that sits atop the master cylinder)?

Thanks for all your input. I'll post what happens.

carguy07

I think this is it, did not see anything about there being a different one for the early cars though.

84460-30040

trhs75

That's the part number I ordered for my '99, also.

Mollymcbut

My 2000 rx300 red brake light was showing so I had all four pads replaced and topped of the brake fluid. the light is still on seem like there might be a reset switch some were in the system will keep t/s and post the results soon .

trhs75

Steady on, not blinking like ours were? Any chime?

maxSteel

Mine just started doing this when the temperature dropped. I assumed it was a sticky parking brake switch. But now it has started to come on/off as I turn corners. It seems to go away as the car warms up.

LA4Mead

Really, this has occured on mine a few times and was so annoying I thought I had to replace the sensor/cap combination right away. But adding more brake fluid above the "max" line silenced the chime and indicator. I'm sure I'll need to replace the sensor someday, but more likely I'll replace all the brakes and purge the fluid before then, then the fluid level will be back above "max" again till the next wear cycle.
When you add more fluid, make sure to keep everything very clean when you remove the cap.
Best from So Cal...

maxSteel

Thanks for the advice, will do.

I was thinking though, why do I need this sensor anyway? I didn't know I had one to begin with. I thought checking the brake fluid level was just typical routine maintenance. So I might just disconnect it and move on.

Lexmex

Also check the voltage of your battery. I had mine disconnected for a bit and realized that when my battery was low, that chime would come on and the brake light would flicker.

pushtree

Replacing the brake fluid reservoir cap is an easy fix, about a minute of time, and it cured the problem. I think the part # is 84460-30040