another brake problem on my 92
Thread Starter
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Joined: Apr 2012
Posts: 87
Likes: 16
From: Midway Ga
another brake problem on my 92
I flushed most of the fluid from my brake system today and bled all the brakes. As I had stated in a previous post , my brakes started getting mushy last saturday and found that the fluid had turned very dark.
During my test drive the dash brake light came on and now stays on . I assume that the sensor is activated by a certain pressure.
I hit the brakes hard several times before the light stayed on and was wondering if there might have a temp sensor as well.
The only circuit that I was unable to flush was the line to the abs unit, I found a bleed fitting on the part behind the drivers seat, but I am unsure of the procedure .
During my test drive the dash brake light came on and now stays on . I assume that the sensor is activated by a certain pressure.
I hit the brakes hard several times before the light stayed on and was wondering if there might have a temp sensor as well.
The only circuit that I was unable to flush was the line to the abs unit, I found a bleed fitting on the part behind the drivers seat, but I am unsure of the procedure .
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
Unless your parking brake is on, the only other thing that should turn on the red brake light is the fluid level sensor in the master cylinder reservoir.
I'm not looking at mine so I'm generalizing here, but usually they have a float inside of it and the sensor is underneath it. I've seen the floats get stuck from all the crap, and I've seen the crap cause the sensor to sense low fluid even though it was fine.
Make sure the float (if it has one) is not stuck. You might try unplugging the sensor and plugging it back in. I did this and even removed it one time, and it fixed it. Not sure why, but it did.
Obviously, make sure you actually have enough brake fluid in the system.
I'm not looking at mine so I'm generalizing here, but usually they have a float inside of it and the sensor is underneath it. I've seen the floats get stuck from all the crap, and I've seen the crap cause the sensor to sense low fluid even though it was fine.
Make sure the float (if it has one) is not stuck. You might try unplugging the sensor and plugging it back in. I did this and even removed it one time, and it fixed it. Not sure why, but it did.
Obviously, make sure you actually have enough brake fluid in the system.
Thread Starter
Advanced
Joined: Apr 2012
Posts: 87
Likes: 16
From: Midway Ga
Thanks 93rubie
I got back in the car last night and no more light. I also noticed another sensor on the bottom of the mc as well. I think I'm gonna pull the sensors and make sure that the ports are not plugged with debris.
I got back in the car last night and no more light. I also noticed another sensor on the bottom of the mc as well. I think I'm gonna pull the sensors and make sure that the ports are not plugged with debris.
Melting Slicks
Joined: Jul 2005
Posts: 2,649
Likes: 863
On the LT1 Vettes - there are actally three things that can make the Brake Light come on:
1. Parking Brake Switch
2. Master Cylinder Warning Switch
3. Master cylinder Fluid Level Switch
I would STRONGLY suggest that you don't try to bleed the ABS unit unless you just replaced it. If the system doesn't have air in it, and you're just flushing the brake fluid, you can just bleed the brakes the conventional way - that will get the lions share of the old fluid out. There will still be a little old fluid in the ABS unit - but if you really want to get that out - the easiest thing is to to go for a ride after a conventional bleed, get the ABS active a few times, then re-bleed the four calipers.
I would also not recommend trying to pull that fluid level sensor in the MC reservoir. While the service manual does not say that you have to bleed things after changing either the warning switch or the fluid level sensor out - it look like the fluid level sensor replacement will empty the master cylinder - so there is certainly Risk of getting air in the system. if the brake light is on and you want to find out why - pull the connector from that fluid level sensor and see if it goes off. If it does - you just found the problem.
1. Parking Brake Switch
2. Master Cylinder Warning Switch
3. Master cylinder Fluid Level Switch
I would STRONGLY suggest that you don't try to bleed the ABS unit unless you just replaced it. If the system doesn't have air in it, and you're just flushing the brake fluid, you can just bleed the brakes the conventional way - that will get the lions share of the old fluid out. There will still be a little old fluid in the ABS unit - but if you really want to get that out - the easiest thing is to to go for a ride after a conventional bleed, get the ABS active a few times, then re-bleed the four calipers.
I would also not recommend trying to pull that fluid level sensor in the MC reservoir. While the service manual does not say that you have to bleed things after changing either the warning switch or the fluid level sensor out - it look like the fluid level sensor replacement will empty the master cylinder - so there is certainly Risk of getting air in the system. if the brake light is on and you want to find out why - pull the connector from that fluid level sensor and see if it goes off. If it does - you just found the problem.
