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Disc brake swap now light coming on (still having issues)

Hmm maybe we are chasing the wrong, system. Could be electrical.
How do the brakes feel? Nice firm pedal? Solid stopping? Stop straight on panic stop? Steady pedal.
Let's take the wire off the switch at the valve. Road test if light comes on is electric, circuit is grounding when weight shifts forward. If stays off then we still have a hydraulic issue.
 
Wes Harden said:
Hmm maybe we are chasing the wrong, system. Could be electrical.
How do the brakes feel? Nice firm pedal? Solid stopping? Stop straight on panic stop? Steady pedal.
Let's take the wire off the switch at the valve. Road test if light comes on is electric, circuit is grounding when weight shifts forward. If stays off then we still have a hydraulic issue.
Click to expand...
No pedal feels mushy, not driving it yet. I dont think it is electrical.
 
Yeah thought on it some more and if light is coming on while stopped in driveway not electrical.
 
formercruiserhead said:
So you have drums in the rear? I just want to make sure that is what you are saying as it is the first time I have heard about using a residual valve on 4 wheel discs.
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Nope 4 wheel disc, and both the valves are on the front reservior line closest to the front of the truck.
 
70jimmy said:
Nope 4 wheel disc, and both the valves are on the front reservior line closest to the front of the truck.
Click to expand...
So I was thinking of using an adjustable prop valve for the rear circuit to restrict flow alittle and help keep the spool in the combo valve from shuttling and tripping the light. Not sure if this would work or is a good idea.
Could you elaborate on your system? What master cylinder do you have? Isthe front reservoir for the front or rear brakes?
 
You are using front calipers on the rear?

One would think the prop valve from a 4 wheel disk setup would solve the issue, but perhaps it's still a volume issue. What size bores were in the rear for the prop and combo valve you used, and what are the ones you ARE using?
 
I
dyeager535 said:
You are using front calipers on the rear?

One would think the prop valve from a 4 wheel disk setup would solve the issue, but perhaps it's still a volume issue. What size bores were in the rear for the prop and combo valve you used, and what are the ones you ARE using?
Click to expand...

I thought the same thing, did some research thinking maybe I had a larger bore rear caliper, but the casting is the same as the front, and not the casting for the bigger bore calipers. Have a reverse bleeder coming will try that have heard they work really well. If that doesnt work then will try the ol rag in the filler neck and match trick.
 
Since I do not own an expensive power bleeder to bleed brake systems, I have found the next best thing to bleed brakes easily and completely are speed bleeder valves. Some people do not like speed bleeders because they only work the first time you use them, and then after that they get clogged with rust and dirt, which causes them to stop working. The mushy brake peddle is a sign of only two things...air in the system or a bad master cylinder.
 
So bought a reverse bleeder on ebay $25. Worked well and pedal very firm. However still get brake light in when push very hard at the bottom of stroke. Used the reverse bleeder 3x. I think some type of residual valve or adjustable on one of the circuits like 70jimmy said just need some more info please.
 
at this point, since you now have a nice firm pedal, all I can think of is the rears(guessing) need so much more fluid than the fronts that the shuttle spool starts to move b4 the pressure equalizes. I haven't had this issue with any of the brake upgrades I've done( no rear conversions). thinking out load here--> One side of the master should move more fluid than the other, this may lead to a solution. Possibly smaller tubing to rear, thou I have concerns about meeting volume needs at rear. rear calipers with smaller pistons ? every oem rear disc brake set I seen has smaller pistons in the rear, except 12000 gvw trucks those are same size brake pads, I would expect the pistons to be the same I haven't actually measured those. Next time I will.
I don't think Blazers came with rear brake load sensing hydraulic valve at rear axle, but if yours has one probably best to remove it.
https://www.turboimagehost.com/p/24152035/mufflers_frame_springs_046.jpg.html
 
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