Brake light coming on?

[Bman]

Okay so for the longest time the brake light was always on in the truck. just yesterday i replaced the front calipers and pads and tried to bleed everything. well the fronts bled fine, but when doing the rears the steel line blew out.

So After get lines and replacing the line i bled them again. everything bled okay. Drove it a bit and came back and re bled the front brakes. Well to my surprise the brake light went off. and now the truck brakes much much better.

The only "issue" is that now if i brake hard or quick the light comes on, but goes out again when i release the brakes. and it only comes on if i brake quickly. and only when im driving.

What could cause this?

 

[firebane]

Brake light coming on usually means low fluid.

 

[Bman]

The Master cylinder is fully topped off. and i mean its as full as it can be. I assume before when the light was always on i had a tripped proportioning valve that now had reset and working again. should i now re bleed everything one more time?

 

[firebane]

The Master cylinder is fully topped off. and i mean its as full as it can be.

You may still have air in the system them. Did you do a proper sequence in bleeding the brakes? And did you have a helper or a 1 man system?

 

[Bman]

is there specific sequence for these trucks? it was me and my uncle.

 

[firebane]

is there specific sequence for these trucks? it was me and my uncle.

By sequence I mean you should start from the furthest point and work closer to the master cylinder.

 

[chengny]

2 X Curtis' suggestion. The brake light comes on for two reasons:

1. The e-brake switch is closed.

2. The "brake failure warning switch" (located within the proportioning/combination valve body) is closed.

Your brake light is coming on because the switch in the P/C valve is moving off-center and closing. It looks like this:

You must be registered for see images attach

When the spool shifts either left or right the switch closes and the dash lamp is grounded - it lights up.

The spool shifts when the brakes are applied and unequal pressure develops between the front and rear hydraulic circuits. This can be caused by the loss of a brake line or excessive amounts of air in the lines.

Since you have repaired your lines and there is no evidence of any further leakage...it would be safe to assume that there is still air in the system.

Repeat the bleeding procedure. Since the line that blew was in the rear circuit, it may be sufficient to bleed only the rear brakes.

Open a bleed valve on one side. Pump the brake pedal slowly and to the floor, do this until no more air comes out of the bleeder. Keep the master cylinder full - the level will quickly drop. On the last downstroke of the brake pedal, hold it there and have an assistant tighten the bleed fitting.

Do the same thing on the other side.

When you are done pump the brakes up - they should feel noticeably stiffer.

If your brake warning light is still illuminated, try resetting the switch by SLAMMING on the brake pedal while the truck is rolling slowly. That usually centers the spool and opens the switch - the light goes out.

 

[Bman]

ahh so the standard pump the pedal then hold while someone opens then closes the bleeder won't work?

because what i noticed was the rear brakes would bleed, but the pedal never would go all the way to the floor when the bleeder was opened. ill have to try bleeding them again and see if it will now that i think the proportioning valve is operating correctly.

but like i said. i only get the brake light comming on when i brake qucikly, if i apply the brakes a bit slower theres no light.

 

[firebane]

ahh so the standard pump the pedal then hold while someone opens then closes the bleeder won't work?

because what i noticed was the rear brakes would bleed, but the pedal never would go all the way to the floor when the bleeder was opened. ill have to try bleeding them again and see if it will now that i think the proportioning valve is operating correctly.

but like i said. i only get the brake light comming on when i brake qucikly, if i apply the brakes a bit slower theres no light.

It happens when you do it quicker because the how much fluid is moving in a moment compared to doing it slowly.

Yes the pump x3 and open the bleeder is how to do it but it has to be timed properly. This is why a 1 man vacuum bleeder is far better and reliable.

 

[Bman]

what do you mean by a 1 man vacuum bleeder?

 

[firebane]

what do you mean by a 1 man vacuum bleeder?

Something like this:
http://www.princessauto.com/en/detail/vacuum-pump-and-brake-bleeder-kit/A-p8050832e

It allows for one person to do the bleeding as it pulls the fluid through. You obviously have to watch your reservoir not to drain it but when you stop getting air bubbles at your fitting close it off and go to the next.

 

[chengny]

but like i said. i only get the brake light comming on when i brake qucikly, if i apply the brakes a bit slower theres no light.


Well, there you go - just never apply the brakes quickly. Problem solved.

Sorry, just f*ckin with ya.

If you can prevent the brake light from coming on - by slowly applying the brakes - that would indicate the presence of air in both the front and rear hydraulic circuits.

I don't know the condition of your bleeders but if you can open the fronts, bleed those lines as well as the rears.

Don't stress about having a bit of air in your lines. These brake systems are amazing when it comes to self-purging during normal operation. The design is such that any air that remains in the lines - after making a repair - will eventually work it's way up to the master cylinder and bubble out.

 

[PrairieDrifter]

The pattern is passenger side rear then drivers side rear, passenger side front, driver side front. That's the pattern on most vehicles,with a few expceptions of course

 

[jt1200r]

Make sure your park brake pedal stays all the way up.

 

[robert8096]

Get you one of these, best thing for bleeding brakes and hydraulic clutches.

http://www.motiveproducts.com/