I know this was covered before countless times, but seriously I need some help.

I have the standard problem, soft break pedal and thus crummy break performance.

Here is the jiffy.
When I bought the car, the break pedal was soft so that in order to stop the car I had to depress it about 1/2 to 2/3 of the way in. Eventually it got worse and I had to press it to the floor.

I took it too a shop to have the breakes bled and master cylinder replaced.

It was better for a while but after a while the breakes started getting worse. I had the car bled and calipers checked... mechanic said everything was in order.

It kept happening, i took it to another shop. Same thing - no leaks.

This happened several times with few different shops.

I eventually took it to a GM dealership they confirmed that there is no leak and said that maybe the air is getting into the system through the booster (?) and suggested replacing master and booster together.

After that I had the brakes bled by a 'corvette shop' - they couldn't find a leak.

So... could it... could it possibly be that my break performance can be improved by a new booster? And if not, what else could be wrong. I guess I can keep having my breakes bled every 30 - 60 days, but even then the performance of breakes is not that great.

How can I improve the performance of my breakes without installing a brand new hydroboost, super titatnium plated, superman enhance break system (ie.. with standard corvette parts)?

PS. when I press on the breakes I definitely hear a 'pressure noise' (pads on a rotor being loose?) coming from the rear.. I had the pads replaced about a year ago and I don't drive that much so I know it's not pads.

Sorry for long post but my magical breakes baffle me.

 

Motive Bleeder.

 

This is assuming all your parts are good.
Probably the least expensive route would be to have all 4 rotors turned true with an "on the vehicle brake lathe", and then as mentioned get a motive bleeder and do it yourself.
No fancy conversions required.

A lot of new cars have the same runout problems with the separate rotors and this is what the manufacturers recommend.

To test the booster, simply apply a hand vacuum pump with gauge to the booster, if it holds a vacuum, it's good.

 

Sounds like you haven't found a real Corvette Shop. Anyone with any experience with these would know how to correct that problem. First of all, you most likely have plenty of runout in the rear rotors. Beyond that a good bleed job will probably fix the problem. The idiot that thinks the system is getting air through the the booster needs to be working on a bicycle.

 

Usually a bad booster causes a hard pedal since it is not "boosting", or the car will start idling poorly or not at all if the booster is bad and leaking vacuum.

If you don't see any leaks and have already replaced the MC, did you replace the flexible brake lines? If not, how old are they? They can go bad on the inside and not be leaking on a visual inspection. A bad one can expand like a balloon when you step on the brakes, causing soft pedal. Eventually it will rupture and leak.

The good news is they are not expensive. you might want to consider replacing them with the SS braided lines like the ones made by Goodridge. Not much more in cost than the flexible rubber lines.

Just a thought on something else you can look at if you haven't already.

 

From responses and what I read on the forum, it definitely is not the booster. Leaky booster will make the braked pedal hard, vs mine is soft.

So this probably means there is a leak or the air is getting somehow. I know that the calipers are not leaking (no leaks around them) but could air be getting in somehow?

Also, any recommendations for shops in Massachusetts (I live in Boston) that would do a good job with a break lathe and bleeding?

 

Have your rear wheel bearings checked for wear. loose rear wheel bearings will cause the rear brake system to slowly fill with air. leading to the problem you just described. How come nobody commented on run out???

 

See www.idavette.net/hib/vette_bbfh.htm part 12 & 13 PG.

 

So the general consensus that it's probably the rear rotors? (and maybe wheel bearings)?

 

Some complain about the caliper original lip seals pumping air in like from rotor runout. Check rotors.

VB&P has O-Ring seal kits to replace the lip seals & a sale on this month.

 

I'll relate a little story,, when i first got my Vette, one of the first upgrades was all new rotors and calipers, i would bleed the brakes to a rock hard pedal, then take it out for a drive. By the time i got back the brakes were always mush, leaving me scratching my head. Every time i bled the brakes after this, i got a ton of air out of the rears, but the fronts were good. I changed the rear calipers to O-ring, which Pretty well solved the problem, then i started getting a grinding noise above 40, one rear bearing failed, it had been bad before, but not bad enough to make any noise. Got both rear trailing arms rebuilt on the car at a local Chevy dealer, while i was there, I had the new rotors machined on the car for run out. That was that, brakes have been perfect since then. Bottom line was, changing the rears to O-rings just masked the problem of the 1 rear rotor wobbling, which causes air pumping on lip seal (original) style calipers. Bleed them and see where the air is. If it's in the rear circuit, 10:1 it's excessive run out on the rear rotors, most common cause for this is a rear wheel bearing going bad. C.

 

This was really helpful. Thank you few questions.
You say you got new rotors - why did you have them machined if they were new, there shouldn't be any runout on new rotors? Or am I missing something.

Assuming it's a runout issue, which it must be after everything i read - can I just get new rotors and then have the bearings replaced? I read that if I have bearings replaced I should replace a spindle nut (what the heck is the spindle nut?)

Here is the deal - after going to several shops that sucked (one 'Corvette' shop forgot to tighten my bolts on my wheels, some of which fell off when I was driving so my wheel almost fell off) I'm most satisfied and happy with my little 'family' shop. They are small, mostly old schoolers that worked on these cars back in the day. The good thing is that he let's me bring in my own parts because sometimes he can't find them in his computer and can't be bothered to chase them down and if he did find them he'd charge me dealer prices. He's happy to work on anything I bring in. So maybe they are not corvette pros, but they do good work, always on the look out for problems, know me and my car so I'll probably go there to get this work done.

To do this can you recommend the things that I should replace. So far I'm thinking:

Bearings from zip
http://www.zip-corvette.com/Zip/prod...893CF4DEC2E125

Rotors from zip
http://www.zip-corvette.com/Zip/prod...893CF4DEC2E125

Should I get anything else to complete the job like they suggest here?
http://www.mamotorworks.com/corvette...-157-1416.html

Thanks for the help.

 

It takes someone that knows what they are doing to setup the rear wheel bearings on these cars as well as a few special tools.

 

Forget the dealership that thinks air gets in from the booster. A Corvette shop that can't find a leak and didn't mention run out, forget them too! If you can you remove the trailing arms your self it will save you some labor charges but either way find a pro. Where do you live, someone will tell you who's good in your area.
You might want to get new SS parking brake parts and SS trailing arm shims and new front TA bushings. PG

 

er, agh

 

I agree with RunningMan on everything but the last statement. Runout is not usually caused by bad wheel bearings. It is caused by bad machining and a lack of knowledge. Most of the time the rotors have already been turned. That is the problem in itself. They have taken a machined unit and split it apart just to machine error into an individual part of the unit, causing runout that wasn't there originally. This is the most common cause of brakes sucking air. If you don't need wheel bearings, there is no use in changing them before you check out the rotors.

 

I would hold up and not try new parts. best is to dianose the problem, and then deciede the route to go. The rear wheel bearings can only be done by a pro, with the correct special tools, they're not like normal bearings, at all. I had my rotors turned because i was sick of messing with the brakes

Rear bearings are also killer expensive, no matter what route you go. I think checking the run out would be your best course. If you can find a decent mechanic at a Chevy dealer, or an old timer at a brake shop, call and ask them if they know how to check the runout on C3 rear brakes. You have to drop the wheels side of the half shaft, then hook up a dial indicator. You or the mechanic will be checking for two things, rotor trueness- or lack there of which can have several causes, and end play, that's where the bearing would show up as being bad. As far as rotor trueness-runout problems go, you can go two routs, 1, you can have them shimmed, or 2, the easier route, you can have them turned on the car with one of the NEW 'bolt to hub' rotor turning machines, both routes are effective, with the 'bolt to hub' machines you need to mark one rotor hole/stud with spray paint or something, because they're now one location only. I would find a competent mechanic to diagnose the runout / endplay issue, then proceed form there. The trailing arms are one of the somabeach jobs to do, for even shadetrees way more experienced then me, i don't know your level of experience, or depth of your pockets, but a good shop i talked to asked for 300 a piece to just pull both T/As. I had mine rebuilt on the car, looked like too much pain for me, but my T/A bushings were serviceable, and I wanted to drive. C.

 

I took a look at the rotors last night and they seem pretty groooooovey and probably need replacement/machining.

Assuming the issues with brakes are because of the runout on motors is there a reason why I should try get them machined rather then just replace the rotors itself. It seems that depending on what quality shop i find there is potential in them doing a crap job - while new rotors will take care of the runout issue. Am I right here or am i missing something?

 

There are two factors that effect rotor trueness, when on the car,, how flat and true the matting surface that makes contact with the hub- if it's skewed the rotor will wobble,, and how flat the rotor is on a 360° rotation. Machining them on the car with one of the NEW bolt to hub machines (not the old machines) solves both problems at once. That's why I had the dealer do mine. Up to you, if you want new rotors or not. If your old rotors are still riveted to the hubs, that might effect your decision, thought removing the rivets is really pretty straight forward. Even if you buy new, you could still be out of spec. C3 brakes are a PITA. fix 'em right, and forget ab out them!!!

 

you might be better off and purchase an assembled unit, less the trailing arm...might be less expensive and might save you time...that is your car won't be appart for any length of time..and you can R&R the assembled spindle yourself...