• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Brake Warning Light - HELP!

PurpleBeeper

PurpleBeeper

Well-Known Member
Local time
1:48 AM
Joined
Mar 20, 2011
Messages
5,383
Reaction score
4,118
Location
Chicago
I replaced the entire brake system except the rear drums/shoes since they've got 70% meat left on them and no leaks or broken parts. New master cylinder, brake booster, distribution block (s), brake lines, front rotors/calipers/pads, new '70 OEM brake warning light sensor...the works.

Now my brake warning light is on & the pedal feels a little "mushy". When I pump the pedal once, it gets firmer. The brakes have been gravity bled 4 times + suction bled (hand vacuum pump) twice PassRear, DR, PF, DF + one gravity bleed with all bleeders open at once.

The local Dodge dealer is stumped too..... any ideas?
 
You still have air trapped somewhere. Being that your warning light is on, try loosening, a line at a time, on the proportioning valve. An air bubble at the switch will make the light come on.

If you said that your brakes felt good but your light is on, you can loosen the pressure switch, just a little to "burp" it. Normally that will fix the "light on" problem.

You have a full pedal after you pump it once, you might need more adjustment on the rear shoes.

Do your front Calipers have the bleeder at the bottom of the piston cylinder. That will make it hard to get the air out of them. (Calipers mounted upside down, like on some aftermarket kits)
 
I would agree but being that he said the dealer was stumped too, that leads me to electrical.

By all means, get the air out but for kicks, unhook the wire at the valve, if it's still on then you are grounded somewhere. Easy check.
 
Don't take this the wrong way McCoy, but would you trust a dealership to work on your 1970 vehicle?
 
Doesn't the parking brake turn the light on too?
 
You guys all bring up some good questions.
Working Before? Not really. It had poor brakes and acted like the master cylinder wasn't right & then the brakes went out completely. The pedal did not go to the floor, but the car would not stop. Thank God I was only going about 5-10mph. I figured I had a master cylinder go bad & replaced the master cylinder and put in a new/correct repro brake booster. I'm not sure if the wire to the brake switch was hooked up before? but now it's hooked up and the light is on.
Grounded? Good question... I will check that. I'm "guessing" no because the pedal feels funny, but yep....I'm "guessing"... I will pull the wire & see if the light goes off. I believe the parking brake switch is OK (yep, also on that light).... but I will double check. If the pedal felt good, I'd be looking closer at this.... but still, I'm guessing.

On that note....can the proportioning valve/distribution block (whichever is where the brake warning sensor screw into) get "stuck" pushed to one side making the light stay on & the brakes feel funny? How exactly does that brake warning sensor work? I have the original valve/block & brake warning switch if needed.
Burping - I may have to go fitting by fitting....this is weird. The brakes do require a second pump sometimes to feel like they're stopping, so my gut instinct is that brake warning light is "real" and not a ground issue.

This "feels" like some strange master cylinder problem. FYI-the driver front & rear flexible brake hoses were replaced too (pass front is older).
Rear Brake Adjustment - Someone else mentioned that too. I pulled just he driver's side drum & it all look OK...no leaks, 70% meat left, no broken/missing pieces, brake adjuster freely moving & set about right. The drum had very slight resistance sliding off & slipped back on "snuggly" without having to force it. Looked good, but I didn't check passenger side....ran out of time & re-bled the master cylinder with the hoses in the reservoirs on the car...didn't work.
Caliper Bleeders - another good question...my bleeders are on top & the calipers are on the correct side. I tried to put them on backwards one time & the flexible brake hose won't bolt up. good question.
Who to Work On It? - Well guys, I'm running out of options. I'm no master mechanic, but I can't figure this shiznit out. The shop up the street said, "??? - no charge". There's one dealer in town that'll touch it & they called in a retired mechanic to take a second look at it, but they're stumped too.
One big problem is that the car was off the road for many years, so I don't have a good baseline for comparison.
 
PurpleBeeper said:
On that note....can the proportioning valve/distribution block (whichever is where the brake warning sensor screw into) get "stuck" pushed to one side making the light stay on & the brakes feel funny?
Click to expand...

The sliding pin in the valve moves to one side or the other, depending on if there's a loss of pressure, front or back. You'll have either front or rear brakes if the pin is out of position. You wouldn't be able to bleed either front or back in this situation. So it should be ok.

Bench bleeding a new mastercylinder, full stroke. You can't always get a full stroke doing this on the car. A common mistake that will leave a pocket of air in the mastercylinder, that won't come out when bleeding at the the wheels.
 
khryslerkid said:
The sliding pin in the valve moves to one side or the other, depending on if there's a loss of pressure, front or back. You'll have either front or rear brakes if the pin is out of position. You wouldn't be able to bleed either front or back in this situation. So it should be ok.

Bench bleeding a new mastercylinder, full stroke. You can't always get a full stroke doing this on the car. A common mistake that will leave a pocket of air in the mastercylinder, that won't come out when bleeding at the the wheels.
Click to expand...

Kryslerkid.... please explain more. Does that "sliding pin" provide ground to an "always hot" brake warning light wire that turns the light on? If yes, then it MUST be slid to one side to make the light come on (unless I have a short). Also, if it is slid to one side, why wouldn't I be able to bleed the brakes? I sure to get plenty of fluid out of every wheel cylinder when I bleed them.

Before I installed the master cylinder I put it in a vise, blocked the holes with the supplied plastic plugs, filled it with brake fluid & pumped it until there were no more bubbles & the piston got super hard to push in. After I installed it and had a brake warning light on, I bled the master cylinder a 2nd time on the car using the little hoses that dump brake fluid back into the reservoir.
 
If it's a one terminal switch, then the switch provides a ground when activated by the pin being off center. The wire is the ground for the circuit, which is normally "open". When the switch is activated it makes "ground" to complete the circuit, which activates the light. Also if the pin is stuck off center it should be blocking either the front or back brakes from any fluid.
Also it was mentioned the the emergency brake switch will activate the light.

Did you pull the wire off of the switch on both?
 
Last edited:
This is a Ford but you get the idea.
20160810_110942.png


Ram man vidio on brake valves.
 
Well, I didn't get a chance to pull the wire off the brake warning switch last night, but I will + I will check the emergency brake. The car is still at the Dodge dealer with a bunch of confused mechanics looking at it. I do have the single-wire push-on-wire type warning switch. If I can get the light to go off by unplugging the brake warning switch, then that tells me the proportioning valve is pushed over to one side or the other & providing a ground (light comes on).

What do you guys think about me pulling out that brake warning switch & poking around with a pick inside the proportioning valve (or distribution block, whatever the switch is screwed into). Maybe that little plunger is stuck from my brake failure?
 
I answered your question on Mopart's before, go look.
Ron
 
Thanks everyone. I see now that the warning switch is in the "metering valve" and the proportioning valve is the other brass block. A guy (ron?) on Moparts said I can re-center the piston by stomping on the pedal 10-15 times & the light should go out, then I re-gravity-bleed. I will check the wire while I'm at it. If that doesn't work, I need to pull the master cylinder (probably swap it out while I'm at it) & figure out how to measure the booster rod 0.910"-0.920" end of rod to face of booster.
 
Short update - I tried the "stomp on the pedal hard 10-15 times" method to re-center the brake warning switch plunger, but the brake warning light didn't go out. I also tried to "feel" if the proportioning valve is working....old tech bulletin a helpful guy on another site posted says I should "feel a small bump" at about 1" of pedal travel when the valve opens while pushing the brake pedal down gently. I didn't feel any "bump" at all. In fact, I can push the pedal to the floor if I push it slowly. When I "stomped" on the pedal, it would go about 1/2 way down before I felt any resistance.
 
I had the same issue this spring when I replaced all my brake components on my 70 RR. Blend with vacuum, stomped pedal and all above tricks. I went right to source and took the pin out of new distribution block for brake switch and replaced it with the one from my factory old one. Well problem fixed, my guess and I have had this problem before with other parts is the machining is off and not to factory specs. The pin was machined different and grounding out. Hope this helps and good luck.
 
If you can push pedal to floor slowly and you have no leaks you have a bad master cyl
 
You must log in or register to reply here.

Similar threads

Eggo
Brake Warning Light
Replies
15
Views
2K
MWbirdLOVER70
MWbirdLOVER70
D
Can't catch a "brake"
Replies
10
Views
867
Dusty Dude
D
Mackman
Low brake pressure
Replies
15
Views
2K
Kern Dog
Kern Dog
Kern Dog
Free play in power brake systems.
2 3
Replies
49
Views
3K
66 Sat
66 Sat
L
Low brake pedal/rolling stop
Replies
6
Views
1K
Ray70Chrg
Ray70Chrg
Auto Transport Service
Back
Top