Brake light on/soft pedal issues
Thread Starter
Instructor
Joined: Oct 2016
Posts: 100
Likes: 0
From: Las Vegas NV
Sounds good. Thanks for your help! I live in Vegas and tomorrow there is a big car show benefiting the victims of Sunday. I really wanted to go. So glad I'll be able to now!
Instructor
Joined: Aug 2017
Posts: 140
Likes: 19
So I ended up ordering a new booster and master cylinder from Vetteco.com. They are really nice, stamped on the MC, and I ended up ordering the booster now rather than later because the new one does have the insert for the deeper hole. The booster and master that were on the car were apparently not as original as I thought.
Anyway, yesterday I got everything installed, including the upper left nut on the booster! Not easy, but with a little patience, it actually didn't take me long. I bled the system, and today, low-and-behold, I stomped on the brake and the brake light flickered. I did it again and went out for good!!! So when I thought the valve was plugged or not working, guess it's all good. Only thing is now, the brake light won't come on when the parking brake is engaged either. Weird. I don't care about that, but I just hope everything is working properly.
Regardless, she runs great, stops better than ever before. I'm very happy today!!
Anyway, yesterday I got everything installed, including the upper left nut on the booster! Not easy, but with a little patience, it actually didn't take me long. I bled the system, and today, low-and-behold, I stomped on the brake and the brake light flickered. I did it again and went out for good!!! So when I thought the valve was plugged or not working, guess it's all good. Only thing is now, the brake light won't come on when the parking brake is engaged either. Weird. I don't care about that, but I just hope everything is working properly.
Regardless, she runs great, stops better than ever before. I'm very happy today!!
Thread Starter
Instructor
Joined: Oct 2016
Posts: 100
Likes: 0
From: Las Vegas NV
So, I spoke a little too soon. Went to a car show last night about 20 miles away. When I got to the exit, began braking and my brake well ALL the way to floor. Scared the crap out of me. It wasn't even like that before I did the work. Then the damn brake light came back on. When I got there, I noticed the MC is leaking around the top (top doesn't look like it was tight and the brand new paint on it corroded off.) I'm hoping it's just air?? Since that brake light went out when I stomped on the brake, maybe there was a bunch of air in that area? I really hope that's all. I've spent too much time/money on these brakes. Everything is new!
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
I wish I could say, ya that's all it was, a pocket of air. We know better. Back to the drawing board. I assume the MC is still full? Something let go, no doubt, scares the hell out of ya. You may not find a wet spot at any of the four corners right away. I found out you can have a leak and not a drop on the floor at first. You need to get the car up on ramps and take a look at all the lines and PV. Then keep pumping the pedal. Now check the calipers REAL CLOSE! Maybe something simple like a defective brass fitting at the MC. You didn't ruin the threads did you?
And WTH? about the paint. Why can't a company that paints a MC use brakefluid-proof paint? That's a no brainer. I was so mad, the paint just wiped right off with a rag on my rebuilt MC. Unacceptable.
Good Luck
And WTH? about the paint. Why can't a company that paints a MC use brakefluid-proof paint? That's a no brainer. I was so mad, the paint just wiped right off with a rag on my rebuilt MC. Unacceptable.
Good Luck
Thread Starter
Instructor
Joined: Oct 2016
Posts: 100
Likes: 0
From: Las Vegas NV
I wish I could say, ya that's all it was, a pocket of air. We know better. Back to the drawing board. I assume the MC is still full? Something let go, no doubt, scares the hell out of ya. You may not find a wet spot at any of the four corners right away. I found out you can have a leak and not a drop on the floor at first. You need to get the car up on ramps and take a look at all the lines and PV. Then keep pumping the pedal. Now check the calipers REAL CLOSE! Maybe something simple like a defective brass fitting at the MC. You didn't ruin the threads did you?
And WTH? about the paint. Why can't a company that paints a MC use brakefluid-proof paint? That's a no brainer. I was so mad, the paint just wiped right off with a rag on my rebuilt MC. Unacceptable.
Good Luck
And WTH? about the paint. Why can't a company that paints a MC use brakefluid-proof paint? That's a no brainer. I was so mad, the paint just wiped right off with a rag on my rebuilt MC. Unacceptable.
Good Luck
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
There is always that very slight possibility of a bad (new) master cyl. I have heard it happens. I sent my first replacement back. Would not hold pressure, so I never got to drive it like you did. Second unit I paid a little more and its on the car now.
On the front and rear line ports of the master, you didn't put a hardware bolt in there as a plug, did you, to test the MC?
On the front and rear line ports of the master, you didn't put a hardware bolt in there as a plug, did you, to test the MC?
Last edited by HeadsU.P.; Oct 9, 2017 at 04:44 PM.
Thread Starter
Instructor
Joined: Oct 2016
Posts: 100
Likes: 0
From: Las Vegas NV
Update:
After all of the above issues, I went ahead and bled the heck out of the system again. Ran about 3 or 4 quarts through it. Air seemed out so I went and did it again, and the rear right still appeared to have bubbles coming out, but I wasn't sure. Anyway, I went and test drove it and the brake felt really good. And the brake light went out when I stomped on it. So, good to go right? Wrong.
I just went to another car show. I was driving down the highway like last week and when I got to my exit, brake pedal to the floor, brak light back on. I'm at a loss. I don't know what the heck else I can do. Has anybody had anything like this?? Oh, and HeadsUP, my MC looks like even more crap now. The cap wasn't super tight so I was able to bend it a bit in the middle to make it snug, but oil is still leaking on the sides. The paint is total crap now. I feel defeated at this point. I've worked so hard and I'm worse than when I started. I'm at a loss.
After all of the above issues, I went ahead and bled the heck out of the system again. Ran about 3 or 4 quarts through it. Air seemed out so I went and did it again, and the rear right still appeared to have bubbles coming out, but I wasn't sure. Anyway, I went and test drove it and the brake felt really good. And the brake light went out when I stomped on it. So, good to go right? Wrong.
I just went to another car show. I was driving down the highway like last week and when I got to my exit, brake pedal to the floor, brak light back on. I'm at a loss. I don't know what the heck else I can do. Has anybody had anything like this?? Oh, and HeadsUP, my MC looks like even more crap now. The cap wasn't super tight so I was able to bend it a bit in the middle to make it snug, but oil is still leaking on the sides. The paint is total crap now. I feel defeated at this point. I've worked so hard and I'm worse than when I started. I'm at a loss.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Just remembered you saying that it seemed like air was leaking past the bleeder screw threads when you were bleeding that particular caliper. I had the same issue on two out of six bleed screws. Went to NAPA got a few new ones. When I installed, I applied a dab of anti-seize on the threads. Then snug it down. When you go to open the screw again, just barely crack it open. Any farther and air will leak past the threads. That was when using the vacuum tool.
On the MC lid: I have found that some companies that make the rubber gasket, made it just a tad too small. Had to search and buy a couple brands to get the proper fit. And I have seen the Bails of different heights also. Had some really nice chrome ones but they wouldn't seal the lid, too short.
Paint: Summit Racing has a "chassis" paint that so far is unaffected by brakefluid. Its satin black and will make that new MC look better.
Leak: You still have a "pisser" somewhere. I suspect the piston seals in one of the calipers. But which one? Which one had air at the bleeder screw? Keep at it!
On the MC lid: I have found that some companies that make the rubber gasket, made it just a tad too small. Had to search and buy a couple brands to get the proper fit. And I have seen the Bails of different heights also. Had some really nice chrome ones but they wouldn't seal the lid, too short.
Paint: Summit Racing has a "chassis" paint that so far is unaffected by brakefluid. Its satin black and will make that new MC look better.
Leak: You still have a "pisser" somewhere. I suspect the piston seals in one of the calipers. But which one? Which one had air at the bleeder screw? Keep at it!
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Le Mans Master
Joined: Aug 2006
Posts: 7,427
Likes: 1,560
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Hi Danny,
You may have a case of 'rotor run out'.
A warped rotor or bad bearings can cause a 'good' firm pedal to get soft.
How to check:
https://www.nucapperformance.com/bra...gn-install.php
You may have a case of 'rotor run out'.
A warped rotor or bad bearings can cause a 'good' firm pedal to get soft.
How to check:
https://www.nucapperformance.com/bra...gn-install.php
Thread Starter
Instructor
Joined: Oct 2016
Posts: 100
Likes: 0
From: Las Vegas NV
Just remembered you saying that it seemed like air was leaking past the bleeder screw threads when you were bleeding that particular caliper. I had the same issue on two out of six bleed screws. Went to NAPA got a few new ones. When I installed, I applied a dab of anti-seize on the threads. Then snug it down. When you go to open the screw again, just barely crack it open. Any farther and air will leak past the threads. That was when using the vacuum tool.
On the MC lid: I have found that some companies that make the rubber gasket, made it just a tad too small. Had to search and buy a couple brands to get the proper fit. And I have seen the Bails of different heights also. Had some really nice chrome ones but they wouldn't seal the lid, too short.
Paint: Summit Racing has a "chassis" paint that so far is unaffected by brakefluid. Its satin black and will make that new MC look better.
Leak: You still have a "pisser" somewhere. I suspect the piston seals in one of the calipers. But which one? Which one had air at the bleeder screw? Keep at it!
On the MC lid: I have found that some companies that make the rubber gasket, made it just a tad too small. Had to search and buy a couple brands to get the proper fit. And I have seen the Bails of different heights also. Had some really nice chrome ones but they wouldn't seal the lid, too short.
Paint: Summit Racing has a "chassis" paint that so far is unaffected by brakefluid. Its satin black and will make that new MC look better.
Leak: You still have a "pisser" somewhere. I suspect the piston seals in one of the calipers. But which one? Which one had air at the bleeder screw? Keep at it!
Thanks for the tip on the paint. Honestly, I don't even care anymore about that. If I can get to it one day I will. Right now, I just want to damn thing to stop without scaring the crap out of me!
Thread Starter
Instructor
Joined: Oct 2016
Posts: 100
Likes: 0
From: Las Vegas NV
I just remembered something...when I bought the car, he told me that his mechanic recommended the right wheel bearing be replaced soon. Any chance that has something to do with this?! That's the wheel where the air bubbles kept coming out.
Pro
Joined: Mar 2005
Posts: 635
Likes: 118
From: Lakemont, GA
Danny,
Yes, it very well could. Anything that makes the rotor move back and forth inside the caliper will shake the caliper pistons and introduce air into the system. On both the occasions that your pedal hit the floor you were coming off an exit, which makes me think that you had been running on the highway - the place that this will happen.
Do you have a pulsing pedal when you stop? Maybe more brake dust on one wheel?
You can jack it up and see if there is any movement in the wheels, if there is this could be your problem.
Good luck and keep it up, these cars are a little finicky but when you do get it right they are very rewarding.
Yes, it very well could. Anything that makes the rotor move back and forth inside the caliper will shake the caliper pistons and introduce air into the system. On both the occasions that your pedal hit the floor you were coming off an exit, which makes me think that you had been running on the highway - the place that this will happen.
Do you have a pulsing pedal when you stop? Maybe more brake dust on one wheel?
You can jack it up and see if there is any movement in the wheels, if there is this could be your problem.
Good luck and keep it up, these cars are a little finicky but when you do get it right they are very rewarding.
Thread Starter
Instructor
Joined: Oct 2016
Posts: 100
Likes: 0
From: Las Vegas NV
Danny,
Yes, it very well could. Anything that makes the rotor move back and forth inside the caliper will shake the caliper pistons and introduce air into the system. On both the occasions that your pedal hit the floor you were coming off an exit, which makes me think that you had been running on the highway - the place that this will happen.
Do you have a pulsing pedal when you stop? Maybe more brake dust on one wheel?
You can jack it up and see if there is any movement in the wheels, if there is this could be your problem.
Good luck and keep it up, these cars are a little finicky but when you do get it right they are very rewarding.
Yes, it very well could. Anything that makes the rotor move back and forth inside the caliper will shake the caliper pistons and introduce air into the system. On both the occasions that your pedal hit the floor you were coming off an exit, which makes me think that you had been running on the highway - the place that this will happen.
Do you have a pulsing pedal when you stop? Maybe more brake dust on one wheel?
You can jack it up and see if there is any movement in the wheels, if there is this could be your problem.
Good luck and keep it up, these cars are a little finicky but when you do get it right they are very rewarding.
Oh, as far as pulsing, could you describe what a "pulsing" would feel like? At this point, I don't know what it should even feel like if it where perfect.
Melting Slicks
Joined: Jul 2010
Posts: 3,176
Likes: 633
From: perth western australia
Pulsing pedal , is when you push your foot down hard enough to engage the brakes to slow the car , you can feel the pedal pushing back up in a rhythmic pulse .
What causes this is when you push down , you put a force on the brake fluid (which doesn't compress) so something has to give , so the brake pistons get pushed into the brake rotor and squeeze it . Now if the rotor is warped it will try to push the piston(s) back up into the caliper as the warped part of the rotor goes past it (them) so it sends a pulse of extra pressure back up the brake line and into the master cylinder bore and ends up against the rod from the brake pedal ,which pushes back on your pedal/foot .
That's why air in the system ruins it as air IS compressible.
Last edited by bazza77; Oct 22, 2017 at 05:49 PM.
Pro
Joined: Mar 2005
Posts: 635
Likes: 118
From: Lakemont, GA
Pulsing pedal , is when you push your foot down hard enough to engage the brakes to slow the car , you can feel the pedal pushing back up in a rhythmic pulse .
What causes this is when you push down , you put a force on the brake fluid (which doesn't compress) so something has to give , so the brake pistons get pushed into the brake rotor and squeeze it . Now if the rotor is warped it will try to push the piston(s) back up into the caliper as the warped part of the rotor goes past it (them) so it sends a pulse of extra pressure back up the brake line and into the master cylinder bore and ends up against the rod from the brake pedal ,which pushes back on your pedal/foot .
That's why air in the system ruins it as air IS compressible.
What causes this is when you push down , you put a force on the brake fluid (which doesn't compress) so something has to give , so the brake pistons get pushed into the brake rotor and squeeze it . Now if the rotor is warped it will try to push the piston(s) back up into the caliper as the warped part of the rotor goes past it (them) so it sends a pulse of extra pressure back up the brake line and into the master cylinder bore and ends up against the rod from the brake pedal ,which pushes back on your pedal/foot .
That's why air in the system ruins it as air IS compressible.
Melting Slicks
Joined: Jul 2010
Posts: 3,176
Likes: 633
From: perth western australia
I bought my 2001 commodore cheap because it had all those symptoms , new rotors and pads all round and its good as new now.
Thread Starter
Instructor
Joined: Oct 2016
Posts: 100
Likes: 0
From: Las Vegas NV
Pulsing pedal , is when you push your foot down hard enough to engage the brakes to slow the car , you can feel the pedal pushing back up in a rhythmic pulse .
What causes this is when you push down , you put a force on the brake fluid (which doesn't compress) so something has to give , so the brake pistons get pushed into the brake rotor and squeeze it . Now if the rotor is warped it will try to push the piston(s) back up into the caliper as the warped part of the rotor goes past it (them) so it sends a pulse of extra pressure back up the brake line and into the master cylinder bore and ends up against the rod from the brake pedal ,which pushes back on your pedal/foot .
That's why air in the system ruins it as air IS compressible.
What causes this is when you push down , you put a force on the brake fluid (which doesn't compress) so something has to give , so the brake pistons get pushed into the brake rotor and squeeze it . Now if the rotor is warped it will try to push the piston(s) back up into the caliper as the warped part of the rotor goes past it (them) so it sends a pulse of extra pressure back up the brake line and into the master cylinder bore and ends up against the rod from the brake pedal ,which pushes back on your pedal/foot .
That's why air in the system ruins it as air IS compressible.
It could be those rear bearings or rotors. I can't believe I'm basically back to square one.
Pro
Joined: Mar 2005
Posts: 635
Likes: 118
From: Lakemont, GA
Keep going, this is a great hobby, but can be trying at times.
Thread Starter
Instructor
Joined: Oct 2016
Posts: 100
Likes: 0
From: Las Vegas NV
You are not at square one, you have a solid booster and master (that are installed properly) and understand where you are getting air in the system. I understand your frustration and have been there myself.
Keep going, this is a great hobby, but can be trying at times.
Pro
Joined: Mar 2005
Posts: 635
Likes: 118
From: Lakemont, GA
Here are some things that you can do to isolate the source of the air:
- Fully bleed the brakes (you are probably an expert at this by now).
- Inspect all brake lines, hoses and fittings for leakage.
- Drive on some back roads (not a lot of traffic) and try to run at some different speeds. apply the brakes and see if you have any vibrations or pulsing. Compare the pedal feel to the just bled brakes.
- If the pedal starts to get soft get back home. Bleed the brakes and look for bubbles from each cylinder.
- If the bubbles start immediately when bleeding from a caliper, the source is that caliper, if it takes a while to get bubbles it is from a line or fitting most likely.
- If it is from one of the rears, you could have a leaky seal, bad bearing or warped rotor.
The brakes in a good working C3 are really very good brakes and should feel as smooth as a new car. My current project has brakes from a 1984 and they have considerably less stopping power.
Keep going, we're pulling for you!