vvv90

So I bled the brakes this week and there was A LOT of air in the line. I got all the air out and brakes are solid now. Pedal doesn't go to the floor at all.

In fact, I can lock them up repeatedly. They feel great!

However, my brake light comes on when I come to a stop. ALSO, the brake light comes on under heavy WOT accelleration.

Since it comes on under accelleration I'm assuming it must be a bad sensor or something.

So what do you guys think? Where should I start? Did this happen to anyone else?

(P.S. The car has been sitting for quite some time, maybe a couple years, it might have something to do with it.)

Zorro4153

The fluid may be low, when stopping and starting, the fluid moves and trips the sensor. Just a thought. If not, I would say a bad sensor

jhammons01

Your rear pads are needing to be replaced. Heat and expansion is enough to turn the light off after warm up but soon it will stay on all the time.

Zorro4153

If the pedal is high and firm while braking and the light come on during WOT accelleration, how does the rear brake line thickness come into play ? I've seen cars with no brake lining left and the light didn't come on. Light will only come on when it's low or a pressure loose and the pedal goes to the floor.

jhammons01

The pedal height is not dictated by the pads. Every time the pedal is let off it should self adjust all the way to where it is metal to metal

I'm not 100% sure on Vettes. You say the car has been sitting up, put new pads on and see.

I know for decades, when my brake light stays on, I change the rear pads and it stops. I never bothered to find out exactly what sensor system is used to sense this.

jfb

Your brake lights are supposed to come on when you stop! Or do you mean the differential brake light warning on the dash comes on when you stop? You need to better describe what kind of fault you are experiencing. If it is the dash warning light, then I would say you have air in one of the systems, front or rear causing a difference in line pressure which activates the differential pressure switch in the master cylinder.

Zorro4153

If it is the dash warning light, then I would say you have air in one of the systems, front or rear causing a difference in line pressure which activates the differential pressure switch in the master cylinder.[/QUOTE]


which will only happen if the brake pedal drops to a point to active the pressure switch. If the pedal is high and firm, it will not active the switch.


Where does the pressure switch come into play at WOT accelleration ??

coupeguy2001

hmmm let me think,

coupeguy2001

everytime you nail it??
Well if you stop grabbing the e-brake handle every time you scare yourself, it won't come on don't deny it, I've seen you drive


Seriously, check the switch on the e-brake handle for adjustment, and the rear e-brake mount bolt for strippage

vvv90

Haha, very funny.

Thank you. I will check those.

vvv90

Oh come on now, seriously. I never said "brake lights" I said "brake light." I give my fellow forum members enough credit to understand what I was talking about.

Right now I'm not banking on any air being in one of the systems.

Like I already said, the pedal is firm. It's also high. NEVER comes close to going to the floor, no need for pumping, etc.

The brakes feel great! The car stops on a dime with repeated threshold braking and bedding attempts.

If the "Differential brake warning light" is coming on under accelleration I STILL do not see how that would indicate air in the "systems."

Of course I could be wrong.

It's the WOT with "differential brake warning light" activation that's got me wonderin'.

jhammons01

Sorry that nobody has posted any other suggestions.

But just try the pads and see what happens. Couldn't be more than a $40 investment in pads and probably 1 hour to change just the rears.

If it is the pads being low and you're problem is solved.......and you also feel bad about not having the Rotors turned, then you can go back and do all the brakes the proper way.

I'd just hate to see you rip out all these other systems looking for a problem that could be solved with $40 bux and 1 hour.

vvv90

Agreed. I will check the pad thickness on the rears. They should probably be changed anyway. The fronts have only a few thousand miles but the rears haven't been changed in 56k (original) miles. I would think they'd be ok but who knows.


Still stumped on the WOT brake light warning though. That still doesn't coincide with low pads.

jhammons01

On a limb here....but I'm going with some sort of flexure while under acceleration. You could have bad wheel bearings that are allowing the sensor to be pulled under a load.

Like I said....on a limb as I have no real clue. The Gurus will come along a straighten me out soon. But it isn't about me and you'll get a good answer that may actually help you.

Spill some truth all over the floor (you know who I am speaking to)

jhammons01

I'm not sure but I don't think Pads last as long as old Brake Drum "shoes" used to last. I'm thinking 56k miles would be at the upper limit.

and don't count out the fact that you may have one piston squeezing better than another which would result in one pad being worn quicker than the other three.

vvv90

Thanks for your help, I do really appreciate it!

jhammons01

Well until you find the real answer I haven't done anything yet but inject conjecture. When you change the pads and it doesn't solve your problem then you may say thank you

89 Bob L

Could be a combonation of bad/worn bearings coupled with the brake pads. If the bearings cause some movement along with worn pads, that could explain your two situations. Try swapping out the pads first. In addition, check your master cylinder for the proper fluid level and ensure the caps are on tight.

coupeguy2001

If your car is 89 or newer:
If you never use the hand brake, you need to pull the hand brake lever about a hundred times to adjust your rear calipers.
The rear calipers are adjusted when you pull the hand brake unlike the fronts that automatically adjust.
try that, and see if the light stays out.

vvv90

It's a manual so I always use my hand brake.

However, the car has been sitting for quite a while so who knows. I'll give it a shot.