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Dash brake light always on- master cylinder fluid ok


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Emergency brake was not on when started rv, but the dash brake light won't go out. Got underneath at the brake pedal and the little black disc that pushes the brake pedal switch in is ok. Lately have been having problems getting the dash brake light to go off when releasing the e brake, but up to now always can get it off by pushing the e brake handle more in.   Put in drive and r.v. Would not creep or move, as if brakes were locked.  Put in reverse and moved backward normally. Then put back in drive, took foot off brake and would creep forward normally then suddenly stopped abruptly with a noise that seemed to be coming from the right front caliper area as if brakes suddenly locked. Dash Brake light on the whole time.  Is there an E brake switch that also controls the light that could be sticking? I don't think the rear brake lights are coming on.

Thanks for any ideas!

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Check the brake fluid level it uses the same warning light if it's low. If the fluid is low chances are pretty high you need front brake pads that could explain your noise.

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the way brake shoes are designed, you can back up easier then go forward with brakes engaged .

 

I am guessing your rear brakes are dragging - or heavily engaged.  

Several ways to confirm - 1) jack up one rear wheel, transmission in neutral - wheel should turn easily. IF both sides are in the air, when one wheel turns other wheel will turn opposite direction (I think). 2) check parking brakes - make sure nothing has jammed in cable causing parking brakes to be engaged.

A number of things can be happening inside the rear brake drums - a little harder to get off then regular car.  Many Links in this forum detailing how to do brake job.

I believe the brake light can come on for 3 reasons: 1) parking brake handle not fully released; 2) brake fluid low;3) air in brake lines.

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12 hours ago, DanAatTheCape said:

the way brake shoes are designed, you can back up easier then go forward with brakes engaged .

 

I am guessing your rear brakes are dragging - or heavily engaged.  

Several ways to confirm - 1) jack up one rear wheel, transmission in neutral - wheel should turn easily. IF both sides are in the air, when one wheel turns other wheel will turn opposite direction (I think). 2) check parking brakes - make sure nothing has jammed in cable causing parking brakes to be engaged.

A number of things can be happening inside the rear brake drums - a little harder to get off then regular car.  Many Links in this forum detailing how to do brake job.

I believe the brake light can come on for 3 reasons: 1) parking brake handle not fully released; 2) brake fluid low;3) air in brake lines.

Correct on the first 2. When brake shoes are worn out they do not effect brake fluid level only disks brakes do. His noise appears to be in the front from his description kind of indicating a locked up caliper and worn out front brakes thus the low fluid level.  

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12 hours ago, Maineah said:

Correct on the first 2. When brake shoes are worn out they do not effect brake fluid level only disks brakes do. His noise appears to be in the front from his description kind of indicating a locked up caliper and worn out front brakes thus the low fluid level.  

Air can get into the lines a number of ways. Also moisture can have the same effect.  How long has it been since the brake fluid was completely replaced?

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Thanks for the replies.  Master cylinder is full and float is ok. Plus e Brake light stays on when the master cylinder switch is disconnected. I may put a new mc on and flush new fluid in since its the orig mc.

The e Brake cable is looping near the bottom near the switch. But light stays on even when the switch is engaged when cable straightened out or pressed by my finger.  reached under the truck and took up the slack to release the rear ebrake and now rear brakes aren't dragging, but e Brake light stays on!!

Maybe the rear brakes are dragging or engaged due to the recent cold weather. Cable underneath or rear brakes likely need adjusting? Don't know why e Brake light won't go off.c

Having trouble finding a shop to work on the rear dually brakes. Aren't they just regular drum brakes?

 

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After searching, the master cylinder i need for a 91 v6 has a 15/16 inch bore, not 7/8?.

Having trouble locating one for a 1 ton, may have to get the $200 plus  toyota one. Aftermarket brake master cylinder still availabe anyone know?

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12 hours ago, DanAatTheCape said:

Air can get into the lines a number of ways. Also moisture can have the same effect.  How long has it been since the brake fluid was completely replaced?

Air in the system will give you a very poor brake pedal it will not lockup brakes. Water is bad thing but it too is a fluid that will not compress so in fact a brake system would work with nothing but water in it (not recommended) The warning light has two switches one for the parking brake the other for the fluid level they complete the ground path, the positive is feed from the "engine" fuse the only other connection to the circuit is a ground signal from the two switches to a factory cruse control module it kills the cruse if the parking brake is on or the fluid level is low kind of a moot point because I believe it was only used on V6 powered vehicles. If either switch is toes up i.e. stuck on or shorted to ground the light will burn. The master cylinder has a connector at the master cylinder fill the other is at the parking brake under the dash with both disconnected the light should not light. Your rear brake lights have nothing to do with the dash light.

Edited by Maineah
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11 hours ago, odysseybernard said:

Thanks for the replies.  Master cylinder is full and float is ok. Plus e Brake light stays on when the master cylinder switch is disconnected. I may put a new mc on and flush new fluid in since its the orig mc.

The e Brake cable is looping near the bottom near the switch. But light stays on even when the switch is engaged when cable straightened out or pressed by my finger.  reached under the truck and took up the slack to release the rear ebrake and now rear brakes aren't dragging, but e Brake light stays on!!

Maybe the rear brakes are dragging or engaged due to the recent cold weather. Cable underneath or rear brakes likely need adjusting? Don't know why e Brake light won't go off.c

Having trouble finding a shop to work on the rear dually brakes. Aren't they just regular drum brakes?

 

Why are you going after the rear brakes when you said the noise was in the front? They would be a whole lot easier and considerably cheaper  to check first and yes by all means they can lockup with a seized caliper (pretty common with age) the greater breaking is done in the front of any vehicle by a wide margin due to weight shift so brake ware is generally 50% faster. No noise in the front end can be a good thing no matter what it is. The rears are a PITA to even look at because the axles and bearings have to come out first (lots of labor) in order to remove the drums.

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Thanks Linda!  I passed that one by since it said 4wd, but you're correct, the numbers cross check. Have ordered and my plan is to replace the Mc and bleed the brakes. Have the RV in storage with high humidity plus recent below zero temps, lockup may be water related.

Not sure if noise is from front or rear brakes, but am thinking rear since if I reach under and release the ebrake cable there is no lockup.

Can't figure out why dash brake light stays on even after disconnecting both switches. Maybe alternator? But charge light is not on.

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It is a connection to ground that lights the light the power is provided by the "engine" fuse with the key on.

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Thanks  for the replies. Will try pulling the fuses. The light showed up after I did a t100 cluster swap, I'll throw the old cluster back in to see if it goes away. I did have to solder 2 circuits together to get the ect light to replace the airbag light, but they are on the other side of the cluster from the brake light circuit. Just assumed it was for real since I know the brakes were grabbing/locking.  I know the ebrake cable was not releasing all the way.

 

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I believe you have solved your problem. Pulling the fuse out will put the light out but not fix the problem and will cause a number of other things not to work. The issue is grounding of the circuit if you jumpered a trace in the replacement cluster you produced a ground for the ebrake light. When you turn the key on the power is supplied to one side of the light circuit only, it stays on as long as the key is on when you pull on the parking brake the switch completes the circuit to ground lighting the lamp it's not a + 12 volt problem it is a - 12 volt problem. It is very possible the way the trace is jumpered it may make it impossible to have it both ways with out adding a diode to the circuit.

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Yes, the new t100 cluster made the dash brake light stay on, just a coincidence happened at the same time the brakes were sticking. 

Per the info in the current electrical section thread about the cluster swap, I had to reposition the yellow wire to the P terminal to smooth out the tach needle, but I had left the red wire where it was instead of disconnecting it. Now the light is out. Soldering the two circuits in the 2nd picture gave me the ect (former airbag) light back.

Going to replace the 27 year old master cylinder and bleed the brakes next.

IMG_20180124_140603844.jpg

IMG_20180124_140553033.jpg

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On 1/23/2018 at 10:51 AM, Maineah said:

Air in the system will give you a very poor brake pedal it will not lockup brakes. Water is bad thing but it too is a fluid that will not compress so in fact a brake system would work with nothing but water in it (not recommended) The warning light has two switches one for the parking brake the other for the fluid level they complete the ground path, the positive is feed from the "engine" fuse the only other connection to the circuit is a ground signal from the two switches to a factory cruse control module it kills the cruse if the parking brake is on or the fluid level is low kind of a moot point because I believe it was only used on V6 powered vehicles. If either switch is toes up i.e. stuck on or shorted to ground the light will burn. The master cylinder has a connector at the master cylinder fill the other is at the parking brake under the dash with both disconnected the light should not light. Your rear brake lights have nothing to do with the dash light.

I mentioned water (moisture) , as that is common in older vehicles that have not have the brake fluid replaced periodically.   Since water causes rust, and rust can cause mater cylinders to freeze in various positions - including expanded -- resulting in locked brakes.

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Drove the Odyssey home from storage, rear brakes locked up going about 5mph with rear tires skidding. Managed to drive home the back way very slowly without using brakes. Changed the master cylinder out and flushed all 5 bleeder valves. (Used a 10 mm 6 point socket after pb blaster to crack each bleeder first since they were pretty rusted). Fluid was dark brown. Original aisin MC I think. Drove for an hour and brakes are now normal so am cautiously optimistic.

Thanks for the replies.

IMG_20180127_141720896.jpg

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Rusted up brake drums from sitting can cause them to lock too until the shoes wipe the rust off. Changing the brake fluid can never be a bad thing (unless you screw it up) brake fluid is hygroscopic so it can absorb moisture one of the biggest issues with water in the fluid is brake fade.

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It could have just been rusty brake drums as well, but a few threads I read said a new master cylinder fixed brake lockup.  Since I was going to bleed them, I didn't want to push the crude out of the 27 year old master cylinder into the brake lines, thus time for a new one anyway.  Hopefully the lockup won't return; sure is dangerous. 

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I had brake lock too. Brake fluid has completely separated and was thin watery stuff and solid goo. I couldn't wait for a new master cylinder to be shipped so I rebuilt my old one. All has been fine for over a year but now my power booster has started leaking. It's always something isn't it.

Linda S

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Haven't got in there to work yet. Rainy season here. It's possible since I did the MC rebuild myself but friend who has worked on these Toyota's for years thinks it's the booster from my description. Told me to test it like this, step on the brake with engine off and it feels firm, without taking foot off brake start engine. If it then goes down to floor it's the booster diaphragm leaking. That's exactly what mine does.

Linda S

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The boaster really should have little effect on the pedal travel running or not yeah it will be hard if the engine isn't running but that's normal it has no connection to brake fluid it's strictly a mechanical device that makes it easier to apply the brakes. If the pedal slowly goes down with light pressure on it the master cylinder is bypassing (leaking internally). If you remove the master cylinder and there is any oily substance it's from the master cylinder there is no oil in the brake booster. 

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So finally looked at the master cylinder that I got from Rock Auto. Beck Arnley so I thought it would be a good one But. The master cylinder looks right but it's got a reservoir with no sensor. That can't be right. Reservoir looks smaller than mine too. I'm going to send it back but how could this happen. They even show correct Toyota part numbers as equivalent. Can't get by without that sensor can I.

Linda S

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Linda,

I just put the rock auto beck arnley mc in last week.

I bench bleed it before I put it in and it's working great. It did come with its own sensor but the connectors were a little off( same shape but would not fit without some trimming) so I just reused my old sensor and float and cap. Didn't notice if the reservoir size was a little different but I don't think it really matters. It was new not rebuilt, good deal for $55,. Much cheaper than OEM. I kept my old original aisin and am gonna rebuild it for kicks.

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Yes the year is what matters. Looks like the bore size got slightly bigger in 1989. Checked with some other 4 cylinder owners and they all have the sensor like my original one. Installing a no sensor one would have meant my brake warning light would have been always on. Beck Arnley dropped the ball on this one. I returned it and have already purchased a Dorman one that looks exactly like mine with the sensor. No trips planned so I have time to wait. Just lucky I checked it. It's just like me to not even look until I'm ready to do the work.

Linda S

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