93 Brake pedal very hard to push

[tim1]

I just joined the vet world and am amazed at the knowledge you guys have. My 93 Vet brake pedal is extremely hard to push for normal braking. I have yet to pull the rims off to start checking pads and rotors, its in a body shop right now. What should I check for besides calipers and pads? My better half does not like to drive it because the brakes are so difficult to press. Any suggestions on were to start?

 

[John Robinson]

Two thoughts come to mind.

1. The vacuum line is off on the vacuum booster for the brakes. Or it is not working.

2. The previous owner put very hard competition brake pads on the brakes.

 

[tim1]

I am going to check the progress at the paint shop today. I will look at the vacuum lines then also, hope its that essy. The PO did nothing to the car other than let his high school daughter drive it. Maybe I should redefine hard to push as you almost have to stand on the brake pedal to get what is suppose to be poer brakes to slow you down to a stop. If I had to stop quick it might be a bad thing or a bigger accident.

 

[John Robinson]

What you describe to me is what the pedal is like when the brake booster fails and all you have are mechanical brakes without assist.

 

[tim1]

I just got off the phone with the body shop. They want to deliver the car today. He checked the booster and said "the vacuum line is connected, and master cylinder is full to the top with fluid."
Is there a way to test the booster to see if it is functioning properly? The car has a few issues but not being able to stop correctly is fast becoming issue #1. Once I get it back, draining some of the brake fluid to the correct level and then taking it for a test ride to see if that helps.

 

[tim1]

I just read a similiar post and c4cruisers reminded me that my service ASR light is on also. He stated it might be a stuck caliper or piston. This might be another thing for me to check out in the next few days, and then drain refill and bleed the system.

 

[John Robinson]

A stuck caliper or piston would cause the car to pull to the right or left when the brakes are applied.

When you apply the brakes to stop does it seem like nothing is happening and then all of a sudden the car seems as if the brakes have crabbed?

Again the ASR (Automatic Spin Reduction) does utilize the brakes to help control wheel spin but if you had a stuck caliper the car would pull right or left. You could try to turn the ASR off.

 

[tim1]

I have only owned the car for a few weeks and it has been in the body shop most of this time. When the brakes are applied the car does not pull to either side. It is just takes allot more pressure to make the car stop. Nothing like power braking at all.

 

[John Robinson]

How long have you had the car?

How many miles on it?

Do you know the previous owner of the car?

 

[tim1]

I have owned the car for about a month and it has 107000 miles on it. I do not know the PO but I know the service ASR light was on when I bought it. The guy told me him mechanic check the car and found no problems with it. So since I got it the ASR light ahs been on and the brakes have been very hard. I put it in the shop because the left rear quarter panel had a crack in it, they are fixing this and repainting it. I should have it back home in the next couple days, but I can get into the shop and check on little things there. I wont be able to pull rims and chaeck the calipers though.

 

[John Robinson]

One of the things some people do when changing the brake pads is to go for the high dollar competition brake pads. Those pads are very hard and take heat to activate them. They really are not a good choice for a daily driver because they will have a lag in stopping the car until they get some heat in them. With 107K on the car it is safe to figure someone has had to change the pads.

 

[tim1]

I hae tried turning the ASR off and it made no differance it the pressure required to the brake pedal. Hopefully I can get the car back in the next couple of days and check the calipers and pads out. I might even replace the pads just to see if new ones make any change at all in the braking pressure. I will keep you posted and am open to any ideas anyone has. Thanks for helping.

 

[Hib Halverson]

A stuck caliper or piston would cause the car to pull to the right or left when the brakes are applied.

When you apply the brakes to stop does it seem like nothing is happening and then all of a sudden the car seems as if the brakes have crabbed?

Again the ASR (Automatic Spin Reduction) does utilize the brakes to help control wheel spin but if you had a stuck caliper the car would pull right or left. You could try to turn the ASR off.

I agree with "John Robinson". If there's a "stuck" brake piston, the car is going to pull to the opposite side under braking. My guess is this problem with high pedal effort is a brake booster issue.

With respect to "ASR"...

It stands for "acceleration slip regulation" not "automatic spin reduction" and "rear brake intervention" IS one of the stratigies it uses to control rear wheel spin. When the ABS/ASR module detects rear wheel spin, in the case of VIN P engines, the first "step" is spark retard. If the wheel spin continues, ASR will enable throttle opening reduction. Finally, if the wheel spin continues and vehicle speed is below 30 mph, ASR will apply the rear brakes as necessary.

If the service ASR light is on, the first step it to determine what fault code is set in the ABS/ASR controller. There instructions on ABS/ASR diagnostics at:
Corvette Action Center | Tech | Stop to Match the Go - All About C4 Antilock Brakes and Traction Control

 

[John Robinson]

Hib After I sent that post I read my FSM and noticed I had incorrectly written what ASR stood for. Being lazy and old I let it go.

Since he did not have the car handy I thought I would bring up the codes issue later but in retrospect if he goes to the body shop he can pull the codes while there and let us know if he has any.

 

[tim1]

Well I went to the body shop today to have a look. The guys there are bouncing off the walls busy. The body work and paint look great, they are waiting for a left rear quarter panel marker to come in and there is a probelm with the drivers window. They are going to look at the window tomorrow, it is going up farther in the front then it shoudl causing the window to seat outside of the vert top.
Prior to putting it in the shop I took the car to an auto parts store and had them pull codes for me. The only thing that showed up was a 26 QDM fault which when looked up in their manual said it is a Quad Driver Circuit. Nobody has been able to tell me what that might be or what to check. GMJunkie said I should check all chassis grounds before anything else. So when the car is out of the shop thats where I will start. I also plan to reread the FSM on how to pull my own codes and give that a shot.
So another unproductive day but starting to get more help from you guess the experts.
Thanks for all your assistance.
Tim

 

[tim1]

Here is the before pic. I hope this works.

 

[John Robinson]

Window problem

There is a peace that is fastened to the window that locates the corner of the window in the track. It is probably broken.

They should be able to remove the window and fix it. The problem may be getting the part.

Ignore the third picture.

 

[tim1]

John, They expect to open up the door panel tomorrow and find out what needs to be done to fix it. I will keep you posted. I just found a company that can reclear coat my wheels so they stay original and look like new wheels. The restoration has begun and will continue.

 

[93Rubie]

It sounds like you have a problem with the vacuum booster. Here is how I might check it. Start the engine and then shut it off. Press the brake pedal you should hear some hissing noise. Just about all of them do it when you apply the brake. IF the pedal is easier to push and then gets hard, that means it is working normally. Next, I would then take the vacuum line off, make sure you got vacuum going to the booster. Then plug the line with a golf tee or something. Then with the line off the booster and plugged, drive the car, if the brakes feel the same I think you definitely have a bad booster. FYI, they are kind of a PITA to change. One needs to be flexible or young. I got the young part covered and it was not fun for even 23 year old. Lying on ones back under a C4 dash with your feet hanging above your head stinks. I also suggest you remove the drivers seat makes it easier. This is a patience job.

 

[tim1]

Just got an update from the body shop. The window regulator appears to have been replaced recently. He said there is a hook on the back part of the window that stops the back of the window from going past its natural stopping point and there looks to be a place for a hook in the front portion of the window. There is no hook there to stop the window from going past its natural stopping point. He is making some calls to try to locate what the part is and were he can get his hands on it so the window regulator will be complete and make it stop once it is closed at the point it is suppose to be to seal properly. I will let you know more when I find out more info.