Street Rat

No red light but no pedal either. '81 with power brakes. Recently put Wilwood calipers on the front. I was careful to bleed them totally vertical also I never have gotten a rock hard pedal. It's mushy won't pump up when I pump the brakes. I checked the booster and it was holding vacuum. I've bled the mc on the bench too. I'm getting ready to plug the mc ports and see if the mc is holding pressure. I ordered a mc kit just in case. The booster was replaced about six years ago. I don't want that job again. I guess it's possible that I still have air in the system but hard to believe. Too much brake fluid has gone to waste.
Help,
Craig

kansas123

How about your rubber hoses, any chance they are old and collapsed? I suspect that they are pretty new since you put the new system on. Good luck with this, mine have frustrated me much in the years I've owned it.

Street Rat

The brakes have been the worst thing about working on this car. I can't get them right. At least removing the trailing arms had an END POINT.

This is a perpetual problem since I have owned this car.

I am the King of the brake fluid reserves in my state probably.

Craig

Goody

Might want to post your bleeding procedure for others to review. Maybe what you are doing is introducing air... This assumes you have carefully inspecting the lines and unions for possible leaks.

Dusky

I've had a problem on a hydraulic clutch system once. No matter what I did, it would get air in the system. In the end I replaced the hard lines and that cured it. Must've pulled air in somehow through one of the flares without leaking.

mrvette

Hoses are the first most failure point on the hydraulics.....so 4 new rubber hoses......after that, get rid of that silly damn brake switch up front, just remove it, and put a splitter fitting in the front brakes, and the line directly to the forward portion of the m/cyl.....rear line goes directly to rear port of m/cyl.....

bleed them the easy way....drill two small holes in the m/cyl metal top....fill the two sections of the m/cyl, put on the gasket and top clamped down snug...then take the air comp and blow air into say the rear hole first, while bleeding one of the rear brake fittings, then do the other one on same caliper....check fluid level in m/cyl, do same for other rear caliper....do same thing in front, and don't forget to check fluid level in m/cyl when you see nothing but fluid, in each case, the brakes really have no excuse now.....just make sure you have the correct m/cyl for the year of car.....later sharks had just a minor divot in the rear for the booster pin to engage, early sharks had a deep hole in the rear m/cyl piston, and a much longer pin from the booster....so make sure you have them compatible.....

but in general, vacuum sux, and as such you are far better off to change the vac booster for a hydroboost system that runs off the power steering pump.....only THEN will you have a ROCK SOLID brake pedal that can easily stand sharkey on his nose.....

Street Rat

All the rubber hoses have been replaced. There are no leaks.

I use a Motive pressure bleeder. I bench bleed the master cylinder at numerous angles. I start bleeding at the furthest to the closest brake bleeder. I use a special tool to hold the prop valve in a neutral position. I use clear hoses leading to a plastic jug at each wheel. I open each bleeder until the air bubbles disappear then close it. Move on to the next bleeder.

Craig

cagotzmann

Did you bleed the MC while on the car ? Try adding this to your procedure.

https://www.corvetteforum.com/forums...-cylinder.html

Bikespace

That is exactly what I do. All I add is to tap the calipers and junctions to dislodge trapped air bubbles. I also have two jugs, so I do both rear caliper bleed screws at once.

PainfullySlow

Craig, your bleeding method seems like it should be working perfectly so I would suggest looking elsewhere. Out of curiosity are you using rubber brake hoses?

I have no first hand experience with Wilwood calipers but I can tell you from other performance brake upgrades on motorcycles (which is the same basic hydraulic system) that going to braided steel hoses really helped to firm up the pedal. My theory is that these calipers provide a lot more clamping force than stock which is why they brake better but it also means that line pressure goes up a bit. The rubber hoses flex a lot even under OEM pressures. Adding to that, even minutely, can really exacerbate the issue. The steel braid helps to constrain the hose flex and results in a much firmer feel at the pedal. It really is night and day, so much so that literally the first thing I did when purchasing a new motorcycle was to replace them, even before riding the bike.

Anyway, I hope this helps and that you can solve your gremlins.

Street Rat

cagotzmann I am glad that you responded.
I have been reading previous brake threads.
You seem to have posted a wealth of information on this subject in the past.

I have not tried bleeding the mc on the car.

I haven't used the procedure that you had previously explained. It was about compressing the caliper pistons inward and holding them there prior to bleeding.

So there are two additional things that I haven't done that I can try!

Craig

Street Rat

PainfullySlow thanks for the response.

The brake hoses have been replaced with Russell stainless lines so time ago.

Craig

Street Rat

mrvette I have been contemplating adding the Wilwood mc and control valve to the system. I think that would do away with the prop valve and allow front to rear brake bias adjustment.

BUT

What am I looking at price wise for a Hydroboost set up? I'm simply curious as I have been reading threads where guys are doing this conversion.

Craig

Kacyc3

Are you driving the car after bleeding them? I had a similar problem and chased my tail to the point I was contemplating switching the calipers for two piston calipers from newer vettes and GTOs. I found calipers leaking after a stalled dash install project after replacing the calipers I now have brakes that feel correct. Check your rear calipers, if they are not oring they maybe the problem.

Street Rat

Hey Kacy3,
I have been driving the car for some time now with less than a full pedal.
It stops fine I just have hardly any pedal.
.

I did initially have a minute leak at a caliper seal and a prop valve connection.
Both of those were repaired prior to the latest brake work.
I'm using factory type calipers with o rings on the rear calipers (for now).
Eventually I will upgrade to the Wilwood calipers on the rear also.

Craig

Kacyc3

same problem I was having, stopping the car required the pedal to be closer to the floor than the gas pedal. I was also concerned about also pressing the gas pedal if I had to panic stop because it was so low. I assumed my problem was the caliper sucking in air from the rotor runout and when I let it set for that project it finally leaked enough out to show the problem. Replacing my calipers resolved the issue and the brake pedal feels much better but still not like a new car.

Street Rat

The issue with this car's rear rotor runout needs attention.
I set the front rotor runout when I installed the Wilwood calipers.
I have yet to even check the rear run out. I was waiting until I put the rear Wilwood calipers on. No chance of that happening anytime soon though.

I believe I'm going to jack this car up and bleed the rear brakes today.
I'll use the techniques posted in cagotzman's previous posts.
Checking the rear rotor runout while I'm there too.

Craig

kansas123

Wishing you good luck today on the brakes Craig. Most frustrating, been there myself...............

Street Rat

Thank you Sir.

I just wonder if I can get her high enough like cagotzman's photo.

Fixing to find out.

Street Rat

This afternoon I got the rear of the car in the air as in the video link in cagatzman's post above.

The first thing that I noticed when I opened the master cylinder was dark fluid in the rear reservoir.

One of the points in the videos were to check the interior reservoir ports for blockage.
Hell I couldn't even see the ports in the rear reservoir. I had to take some brake fluid out to see the ports. I poked a paperclip in the ports and everything felt clear.
I'm suspecting something is wrong with the master cylinder seals in the rear at this point.

I go ahead and check for bubbles coming from the rear interior mc ports with the rear of the car up. No bubbles are released.

I went ahead and bled the right rear caliper with the Motive bleeder. Everything seemed to be going well until I came back to check on the pressure bleeder.
There was a puddle of fluid under the front of the car.
I checked the prop valve connections. All were dry.

The culprit seems to be the master cylinder as I see fluid being released from the rear of the mc mounting area.

I purchased a mc rebuild kit from CSSB and it has arrived.

So the next chapter is to rebuild the mc tomorrow and try things again.

Craig