brake warning light still on

[capev86]

hi all....

just finished installing all new braided brake hoses and bleeding the brakes (synthetic dot 4) on my 72 burb 2wd, 3/4 ton. the brakes are pretty firm and no sign of leaks, yet the brake warning light came on again after it was all done. receptive to hint right now, ladies and gentleman. night driving is no fun at night with a big red light blaring at you. its not an idiot light i care to live without, so i don't want to pull the bulb.

[72lb4x4]

I think the block (proportioning valve) under the MC has a tan/brown wire on it. When the pressure to the front or rear brakes is too low, the light comes on.

Page 5-24 of the service manual says that when pressure on both sides is equal, the switch will reset. When I had the brakes flushed and bled, they said they had to jump up and down on the pedal to get it to reset...

Also in the manual it says the pin on the end of the prop valve should be pressed in slightly during bleeding. I think its at the front and normally under a little rubber plug. The drawing of the tool shows it to be sort of like an L bracked with an adjustment slot instead of holes on one side.

[Longhorn Man]

side note, DOT4 isn't such a great idea. It doesn't absorb water, so any water vapor that condenses into water becomes section filled with waterr in the lines which causes other problems in the system (ice, rust, leaking by piston seals)
Its also known for being a total pain to bleed, which may actually be your problem.

[fixit-p]

Unplug the wire at the MC if the light stays on there is a short in the circuit.

[capev86]

thanks guys for all the info about the circuit and i forgot about the pin on the prop valve.

as for the dot 4 fluid....it should still be gylcol based like dot 3. i have used it in other cars with no problems. this was a brand new bottle just opened today and i was careful to keep it and the m/c covered as much as possible. thankfully the air is getting less humid by the day (winter). i wouldn't bother with dot 5 because it is silicone based and performance is not consistent enough for heavy duty/regular driver status.

i will check back when i have more to report.....thanks again!

[QKENUF4U]

Originally Posted by capev86

thanks guys for all the info about the circuit and i forgot about the pin on the prop valve.

as for the dot 4 fluid....it should still be gylcol based like dot 3. i have used it in other cars with no problems. this was a brand new bottle just opened today and i was careful to keep it and the m/c covered as much as possible. thankfully the air is getting less humid by the day (winter). i wouldn't bother with dot 5 because it is silicone based and performance is not consistent enough for heavy duty/regular driver status.

i will check back when i have more to report.....thanks again!

you are right and if you did use DOT 5 you would have ALOT OF PROBLEMS being its synthetic and would eat your seals... DOT 5.1 is glycol based and can be used with DOT 3, 4.......
all but DOT 5 (NON COMPATIBLE synthetic) is hygroscopic ... the only thing that changes is the boiling point... being DOT 5 is synthetic moisture still enters the system but it goes to the lowest point in the system and corrodes while it sits there (caliper pistons)
no matter what DOT # ya have you should change it out every year or two.... MITY VAC makes and easy job of that....

[Longhorn Man]

my bad... numbers escape me sometimes.

[capev86]

thats ok....happens to the best of us................and me too for that matter!