Brake light on/soft pedal issues
Thread Starter
Instructor
Joined: Oct 2016
Posts: 100
Likes: 0
From: Las Vegas NV
Rear bearings are a pain, if you need to replace them I would recommend removing the entire trailing arm and sending them to a reputable vendor (there are several on this forum).
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!
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!
Thread Starter
Instructor
Joined: Oct 2016
Posts: 100
Likes: 0
From: Las Vegas NV
So I haven't had any time since this past weekend to do anything, but I just jacked the right side of the car up and for the heck of it, I grabbed both sides of the rear right wheel and there is a decent about of play in it. Now everything I've learned lately about this car is from this forum, and I didn't know a whole lot before I got it, but to me this doesn't seem right. As a novice, I'd have to say that it's starting to make sense with the rear bearings being bad? And this could be a cause of air continually getting into that caliper? Does that kind of make sense?
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Danny,
As posted some time back, someone said when pressure testing the master to block off the two line ports at the master with bolts inserted to see if the MC will hold pressure. He went on to say that the inner ports were cast iron and a bolt would not hurt anything. Looked at my original MC today, off the car, with a bright light. Both front port and rear inner ports are BRASS tapered inserts. So, out of curiosity and looked at a rebuilt unit I had lying around. It too had brass inserts. So please tell me you didn't shove a couple bolts in those ports to test the MC and ruin the brakeline seal.
As far as the rear bearing runout. I really doubt that is the cause of air in the caliper. On the fronts, maybe. On the rears, doubtful because of the trailing arm bearing support.
As posted some time back, someone said when pressure testing the master to block off the two line ports at the master with bolts inserted to see if the MC will hold pressure. He went on to say that the inner ports were cast iron and a bolt would not hurt anything. Looked at my original MC today, off the car, with a bright light. Both front port and rear inner ports are BRASS tapered inserts. So, out of curiosity and looked at a rebuilt unit I had lying around. It too had brass inserts. So please tell me you didn't shove a couple bolts in those ports to test the MC and ruin the brakeline seal.
As far as the rear bearing runout. I really doubt that is the cause of air in the caliper. On the fronts, maybe. On the rears, doubtful because of the trailing arm bearing support.
Last edited by HeadsU.P.; Oct 24, 2017 at 08:02 PM.
Pro
Joined: Mar 2005
Posts: 635
Likes: 118
From: Lakemont, GA
When you get a chance jack up the left side and compare the play.
If you are getting air immediately when you are bleeding the right rear caliper it is most likely caused by bad seals (which would leak as well) or the rotor moving excessively inside the caliper. This movement can be from bearings or from rotor runout. The problem with bearings is that they can behave differently at different speeds.
Not trying to butt heads with HeadsU.P. but bearing slop will cause runout between the caliper and rotor which can lead to air in a caliper.
Thanks, Chris
If you are getting air immediately when you are bleeding the right rear caliper it is most likely caused by bad seals (which would leak as well) or the rotor moving excessively inside the caliper. This movement can be from bearings or from rotor runout. The problem with bearings is that they can behave differently at different speeds.
Not trying to butt heads with HeadsU.P. but bearing slop will cause runout between the caliper and rotor which can lead to air in a caliper.
Thanks, Chris
Thread Starter
Instructor
Joined: Oct 2016
Posts: 100
Likes: 0
From: Las Vegas NV
Thanks guys. Headsup, no, I never did that and put any bolts in there. Plus, I purchased a new MC anyways, so everything is new in there.
I'm going to jack up the other side today to compare. I did the front on the same side and there was no play at all. I have a feeling there won't be any in the left either. So I'll check on that. I feel like the bearings need replacing regardless, because the previous owner told me they would. But, I just hope that's what's causing this issue. I don't want to go through all of the trouble of getting that fixed, and then still have a crappy brake.
I'm going to jack up the other side today to compare. I did the front on the same side and there was no play at all. I have a feeling there won't be any in the left either. So I'll check on that. I feel like the bearings need replacing regardless, because the previous owner told me they would. But, I just hope that's what's causing this issue. I don't want to go through all of the trouble of getting that fixed, and then still have a crappy brake.
Thread Starter
Instructor
Joined: Oct 2016
Posts: 100
Likes: 0
From: Las Vegas NV
So I just jacked the other side up and no play in the weels. The front did very very slightly, but I went back to the rear right and it has about 1/4" of play. It's the worst when I hold the wheel at 12 and 6. When I hold it at 3 and 9, it's has play, but not nearly as much at 12 and 6. Any idea what that means? Bearings or something else?
Either way, I'm not sure if this is what's causing my brake issues. smh
Either way, I'm not sure if this is what's causing my brake issues. smh
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
H-m-m-m-m. At 12 & 6. Maybe bushing at trailing arm or bushing at strut rod. And yes, I agree, not air in brake system related.
Last edited by HeadsU.P.; Oct 25, 2017 at 06:23 PM.
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Pro
Joined: Mar 2005
Posts: 635
Likes: 118
From: Lakemont, GA
So I just jacked the other side up and no play in the weels. The front did very very slightly, but I went back to the rear right and it has about 1/4" of play. It's the worst when I hold the wheel at 12 and 6. When I hold it at 3 and 9, it's has play, but not nearly as much at 12 and 6. Any idea what that means? Bearings or something else?
Either way, I'm not sure if this is what's causing my brake issues. smh
Either way, I'm not sure if this is what's causing my brake issues. smh
https://www.muskegonbrake.com/corvette/technical-faqs
Thread Starter
Instructor
Joined: Oct 2016
Posts: 100
Likes: 0
From: Las Vegas NV
Can you tell when you have movement at 12 an 6 if the rotor is moving in the caliper? If it is bushings in the strut rod, there should be no relative motion but if there is a bearing issue there will be.
https://www.muskegonbrake.com/corvette/technical-faqs
https://www.muskegonbrake.com/corvette/technical-faqs
Pro
Joined: Mar 2005
Posts: 635
Likes: 118
From: Lakemont, GA
I just jacked the rear end up, took the wheels off and put the lug nuts back on to hold the rotors. The right one, which is the one in question, does move a little in the caliper and the axle moves. Also, looking down into the caliper where the piston meets the brake pad, there is oil! So it looks like there is definitely a leak there. I'm at the point where this might be getting over my head. I'm considering just taking it to somebody. Thoughts? I am getting somewhere, but I just don't know how many things need to be repaired!
Without looking at your car it sounds like you do have a bad bearing. This is an issue that needs to be addressed, I have seen them come apart and it is not a good situation. The best fix is to have the trailing arms rebuilt. If you remove the trailing arms there are several very good companies that will rebuild them. If you want to take it to somebody I would start looking for reputable shops in your area. There are a lot of members in your area and they may be able to point you in the right direction.
Once you have the bearing taken care of you can rebuild the caliper and you should be in good shape.
Thanks, Chris
Thread Starter
Instructor
Joined: Oct 2016
Posts: 100
Likes: 0
From: Las Vegas NV
Here is a good video on removing the trailing arms, the assembly he has at the end is what you will send off and get back.
https://www.youtube.com/watch?v=7MaZGAOejGA
https://www.youtube.com/watch?v=7MaZGAOejGA