Hello I have a 96 LT1 C4 that I recently purchased needing a lot of work and the biggest issue so far is the brakes. This post will be very long but I have tried reading all the existing threads I could find regarding brakes but nothing seemed to fix my problem. When I bought the car it had barely any braking power so after checking some stuff I rebuilt all 4 rotors, changed the pads and rotors, installed steel brake lines, installed a new master cylinder(bench bled), and most recently installed a new brake booster and bleed the system. The issue now seems to be I have power assisted brakes for about the first 2 brake applications and then the pedal becomes very hard and you have to really push down to get brake power. However once you let go of the brakes and say drive a bit more and almost seeming like it needs to repressurize then you get about another 2 power assisted stops. Thinking it was a vacuum issue I checked the hose (good), checked the vacuum coming from the engine at idle (at least 18in), and checked the booster (builds and hold vacuum with the gauge). I also read about checking to see if it's ABS related so I pulled the fuse and tested it out (no effect) and also tried stopping multiple times on gravel to see if the ABS was working (everything works).

Could someone please provide some insight as to what the issue may be as it is getting very fustrating that I have replaced pretty much the entire brake system and it still doesn't seem to work (or at least work as other cars). The brakes work but this issue can be very difficult/unnerving in situations like stop and go traffic where you have to make multiple on and off brake applications in a short time fram.

 

Get a cheap cigar and blow smoke with the engine off in differant lines till you find the leak.

 

It seems like you have basically eliminated having poor vacuum. Make sure the hoses are clear and not clasping under vacuum. If you can check the vacuum at the booster while someone presses the pedal to see if the vacuum is changing radically.

I would also consider the booster being defective. If it is under warranty and easy to return/exchange I would consider (I have had parts and boosters that check good but were bad) replacing it. Consider when you are checking the vacuum at the booster the pedal is not depressed. Something may change when the bladder changes shape and a leak may develop.

Note as long as the calipers are working and retracting properly you can forget about the ABS. Having similar problems as you I had replaced everything multiple times and did not make much headway (could not figure it out). I ended up changing to the J55 13" rotor system which did help a lot (and more expensive to maintain). Finding the right pads that worked for me was another part of the puzzle (and don’t know why it should have been such a selection problem). Few years later my booster went bad with a leak and with the new booster the brakes worked great. Want to call it a weak booster be my guest as it had no defective symptoms at all.

 

I would check the Vacuum Check valve.. this is just a General video non vette specific..

 

Thanks for the suggestions! I'll have to recheck the gauge with the pedal depressed. I was afraid of the "brake booster being bad" bad thing as it was so much of a pain to replace in the first place.

Now that you mention about the calipers retracting properly, do you think if they aren't (such as a bad rebuild) I would be getting similar symptoms with the brakes being harder to engage after one or two applications in quick secession?

 

Ok so after I got home from work I did a test like pcolt94 suggested and connected my gauge to the extra port on the new boosters check valve and made a quick video of what happens when the brake pedal is pressed...

 

You did the test exactly right. Your pedal is getting hard because your loosing vacuum. You can forget about the rest of the car and focus on the booster.

I just had a similar symptom 2 months ago as I was looking for a vacuum leak for a hesitation problem. What I found was a bad booster although I was not having any braking problems at that time. The vacuum gauge should only vary a pound or two for a second and come right back up but never drop to 5 pounds.

Just on principal you can inspect the rubber vacuum hose just to make sure it's good but it's a pretty hefty hose. My money is on the booster.

 

Thanks for the help! I guess I just have to accept it is the booster. Not sure where I'm going to go from here as I'm not sure I want to go through the hassle and pain of swapping the booster again.

 

Pain in the A**, yes.

Get-R-done and you'll be happy.

At least your not hunting for the solution to a problem which could go on for a good while.

You do know the masters brake lines do not have to be removed so no bleeding is necessary.

 

I know I'm going to end up having to replace it but I guess seeing how I'm still recovering physically from installing this one makes me want to do it even less haha.

I've heard of people not needing to unhook the master to do the swap but when I tried it I didn't get much room even after unbolting the ASR and was afraid of bending/breaking a brake line so I just unhooked the master.

 

So just to be clear! two booster's and you have the same symptoms, or; did the original booster act differently?

 

No the brake booster that was on the car when I got it provided no power assist and the new one that was just installed a few days ago provides power assist for only 1-2 brake applications in a short period of time until the booster rebuilds vacuum, such as in the video I posted. Just to be sure I did test the old booster off the car with my vacuum gauge yesterday it it doesn't seem to be holding ANY vacuum.

 

OK it sounds like your going down a good path. I would perform the Vacuum test directly on the manifold as well, just to make sure there isn't some sort of obstruction in the manifold..

 

I hear ya, and caution is always good. Yes the ASR has got to be unbolted from the side fender well and bottom support. Then push ASR to the alternator, snug it in there. I do the same with the master, get an bungee cord or such and tie it off to keep it out of my way. Seems like I loosened up the cruise servo also with adds room.

As you probably know, there is a magical way to wiggle it in.

I realize it's a different car but seems like the hard lines seem to flex OK.

A picture from 2010 when I replaced it the first time.

 

If I pull the line off of the booster and connect the line directly from the engine to the gauge I get about/at least 18in of vacuum so I'm pretty sure I don't have a problem with engine vacuum or the vacuum hose.

I picked up a replacement booster from a different source since the first one doesn't have a lifetime warranty and found one from a local pets store with a lifetime warranty for a few bucks more and since they are local I wouldn't have to deal with shipping.

I won't get around installing it til this weekend at the earliest but I'm considering trying a test to confirm the issue before doing so. I'm thinking I will disconnect the vacuum hose from the booster in the car and connect it and the gauge to the one I just picked up the same way I tested the current one last night and see what different results I hopefully get. At least this way I will have some confirmation of the current one being bad before I go through the hassle of removal/installation.

 

OK cool, not a bad idea to test it prier to install

 

Ok well just got done testing it and unfortunately I think I have some bad news. So I unhooked the vacuum line from the booster installed in the car and Hooke it up to the new one I bought today and hooked the gauge to the spare port on the check valve like I did with the previous test. Well it seems that the new one only builds about 10in of vacuum at most and when I push in the rod it drops down basically as much as the other one did but then again it's not raising as high either.

To be sure it wasn't a gauge issue or what it I swapped the gauge and hose to the booster on the car and once again I got about 18in of vacuum and the same drop when th brake was pressed all the way down.

I'm really not sure where to go from here as both boosters seem to have a big drop on the gauge in vacuum and the new one won't even build up as high of vacuum as the one on the car now. I don't think not having it installed on the car would affect that?

Any ideas?

 

Thanks for the image. I'm also looking to replace my booster as soon as I get her out of storage.

 

The only thing I can think of is that there is a restriction somewhere that only allows vacuum to build slowly. Not sure but I thought in your video that it jumped to a high vacuum pretty quickly. You should be able to test this by using your thumb over the hose at the booster end and seeing if there is a constant flow of air into the engine.

 

GOOD NEWS!

Ok well after my previous post I was frustrated and decided hey I've pretty much eliminated the booster itself unless I got two duds (unlikely but not impossible) so I decided to go back and triple check everything. So when I got to the booster hose I removed it and said "Hey it looks really good with no damage but let me try blowing through it" so I gave it all my breath and got LOTS of resistance with very little flow on the other end. I know it's a curvy hose but it's also sturdy and thick so I assumed there should be less resistance and more flow through it. So I took some fuel line hose I have and connected the booster to the engine and redid the test. I got about the same vacuum maybe slightly more but when the brakes were fully applied it only dropped about 5 in of vacuum. So I'm not sure how but apparently the hose is bad/clogged even though it looks good. Took the car for a quick test drive and the brakes feel like they are working correctly minus a bit of a soft pedal and what I think may be a bit too much pedal travel but maybe that's cause I was so used to using so much force on the pedal and now there's hardly any resistance.

So looks like I won't have to change the booster out again! YAY! But now I will have to try to track down a proper replacement hose for the booster. Also I will have to figure out how to go about the returns process as the booster I purchased today had a core charge so I just gave them my old one so I didn't have to pay it but the one that's on the car now also has a core charge (even more then the one from the local store) so I'm not sure if I'm gonna be able to get my old one back when I return the new one so I can get the original core back.

I feel like I jumped the gun on buying a new one or at least returning the core today but without the new booster and the testing that resulted afterward I would have never gotten to this point...