itseybit

We have a problem we have new brakes and have had rotors turned and have bled brakes several time and still we have a soft pedel,don't know where to go from here.which included master cyl.hoses etc. Has anyone had this problem. Thank you for any help you can give ITSEYBIT

Warp70

I had the same problem on mine. I had the front calpiers rebuilt but it did not resolve the issue. I finally had to have the master cylinder and Combination Valve replaced as both were bad. Good Luck!!!

Ken73

90% of the time it seems to be the lousy lip-seals on the original calipers. Best bet is to spend a few bucks (especially since brakes are such an important piece!) and get the Vette Brakes O-ring calipers. I realize they cost a bunch more, but in the long run you WON'T regret it. I'm hoping I can get all three of our Vettes on the O-ring calipers soon. I already have them on my '82 and can't imagine it without them.

If it tells you anything, I used to have to bleed my calipers once a month and eventually once a week - before I finally got fed up and replaced them with the O-ring design. If you already have stainless-steel sleeved calipers, you can buy just the O-ring piston kits and save a lot of money.

redvetracr

Ken73,
It has been said (by smarter people than me) that o-ring pistons simply mask the true problem, which in many cases is air pumping either by out of spec rear rotors or poorly adjusted (or just worn out) rear wheel bearings. I honestly don`t think the problem is the "lip seal" but the corrosion on the pistons under the seal. ...redvetracr

Rockn-Roll

How did you bleed the brakes? Did you attach a hose to a bleeder and stick the other end of it into a jar to catch the fluid, then open a bleeder and pump the brakes? Or, did you just open a bleeder and let the fluid leak out? One of these methods is basically the same as a leak in the system which causes a soft pedal...the other actually gets all the air out of the system and gives you reliable brakes. It seems on this forum everyone has their own opinion on which procedure is a leak.

Ken73

I agree about the air pumping. Someone also had mentioned that the calipers are not "floating" like they are on most other vehicles, so they can't really adjust back and forth for a warped rotor as well as a floating one could. (Anyone have any ideas how to make the calipers float? Bush the bolts?)

Still, the O-ring design may be a "mask" as you say (and I don't argue that either) but it does work, and quite well. I feel it's far superior to the original lip seal design. Also, as far as corrosion, you'll notice that all O-ring setups have stainless-steel sleeved calipers to prevent that.

If anything, Autozone sells stainless-steel-sleeved calipers with the original lip-seals in them for $80 a piece, but for that kind of money could get the O-ring ones from Vette Brakes (although you'd have to send in a core to Vette Brakes and wait for the return, as where you can drop your cores off at Autozone.)

If you *REALLY* want to do it right, get your rotors turned and then put a dial indicator on them to make sure the runout (in place, on the car!) is very low. Shim the studs. This is a very tedious task and I'm not sure how worth it, it is.

gerry72

We've all had the "soft brake pedal" syndrome following what seemed like everything done right in a brake job. If your rotors meet the parallelism specifications, then most likely the problem is going to be in the master cylinder. These cylinders require a very vigorous bench bleed to get all the air out. You won't be able to bleed the cylinder through the calipers. It must be done using the proper method and tools.

Chinaski

what about installing a new master cylinder...how do you bench bleed it?

Ken73

Stick it in a vise, clamp it down tight, and ram a screwdriver in where the pushrod normally goes. There's a little kit that they sometimes provide with the new M/C that has a hose meant to go into your resevoir. That way the fluid just gets pumped back into the M/C while you get the air out.

bigvette1

Needless to say Vette brakes are either very good or very bad. Before you spend anymore money let me suggest:

1. Get a magnetic dial indicator and check the rotor runout on all 4 wheels. Turn the rotor slowly and watch the indicator. If runout is more than spec you will always have a problem getting a bleed that holds. You will get a hard peddle but it will pump air as soon as you start using running.

2. On a new MC, bench bleed it slow slow slow or you are aerating bubbles internaly. When you put it back on check the rod length from the booster if you power brakes. You shoud have about 3/4" free travel before you contact the MC piston. If not adjust it. Just because it worked with an old one does not mean the pistons are the same and rod length will be affected.

3. Did you use silicon or Dot 5 fluid. Frankly you will not get a hard peddle with silicon.

4. New calipers if they are not leaking should be ok, if all else is ok.

4. Read the posts and the book on bleeding methods and sequence. You might want to consider a power bleed also.

Good luck on this common vette problem.

Barry's70LT1

Hi Jim, very good advice.
I can't totally agree with #3. I can only speak from my own experience.
I converted to silicone fluid over 10 years ago. I have a very firm peddle.
No problems at all since I went to DOT5.

Some people have had difficulties using silicone fluid. I don't know what makes one vette work well with DOT5 and others do not.
Barry

redvetracr

Ken73,
The "corrosion" I speak of is found on the piston under the lip seal.
...redvetracr

dennis

Had that problem for years. Replaced with zero tolerance aluminum pistons and "o" rings seals. Was told not to sleeve, just honed my bores, installed and haven't had a problem for 8 years. I believe ZTI was bought out by a caliper outfit. Good luck.

bigvette1

Barry,
Wish I knew the secret of silicon fluid vs regular. I used silicon with all new calipers and the peddle was ok, but when it was hot out it seemed to fade and get a little spongy. I flushed the silicon out and put in new regular fluid, bled it out and had a very firm peddle - what I guess you expect GM power brakes to feel like. No other changes.

Barry's70LT1

Jim,
When you did your brakes with DOT5, did you rebuild the master cylinder as well??
I rebuilt mine when I replaced the calipers.
Just wondering if maybe the M/C is not in good shape, then the DOT5 may not come up to pressure as quickly as DOT3.

From past posts here on the Forum, looks like a rebuilt unit could be far from perfect.
We may never know.
Barry

Tom454

I've been using DOT 5 silicone in my 66 for over 20 years... non-power brakes, and the pedal is hard as a rock. Absolutely no problems with the fluid itself, no fading, no soft pedal, and no corrosion.

When I installed it, I rebuilt the master cylinder and installed SS sleeved calipers.

The fluid itself has remained perfectly clear, and has outlasted 3 sets of caliper seals.

RE redvetracr.... he is right about the area where the outer dust seal rides. This is the first line of defense, and it is where aluminum pistons always fail. I use SS pistons to avoid this problem.

Silicone fluid, stainless pistons & ss sleeved calipers, and rotors with runout within spec have been a winning combo for me.
If the rotors are within spec, you don't need the special pistons/seals.
As posted, they only mask the real problem.
They are a great product, they work, but you don't need them if your runout is within spec.
In fact, they work so well, that the continuous pulsing of out-of-spec rotors causes the pistons to slam against the caliper bore/sleeve. egg-shaping it and eventually rendering the caliper useless.... before the seal leaks. They shouldn't be used as a repair for out-of-spec rotors, and the manufacturer will tell you that.

My 66 has been "in spec" since I bought it in 1975 and I have standard design (but stainless) pistons & seals..... and no problems.
My 70 is "in spec" as well... again... no problems with the brakes.

The inner seals will always go bad over time, no matter what type you buy.

GaryS

If you are going to that much trouble to rebuild your braking system, did you then also replace the four rubber lines? Often these lines will fail internally and cause problems. Others have already suggested getting the master cylinder rebuild kit and putting it in. This is a fairly simple DIY job. As others have stated, it is also possible that you have a bad caliper, even though it is new.
Gary

bigvette1

Barry,
Actually the MC was the origional. I replaced the calipers and flex lines, then used silicon. What you are saying has merit. An old one with margional seals or a rebuiild with margional seals could do the same. I think Silicon is a lesser viscosity than regular fluid and this may answer the question.
Jim

Noel Carboni

By the way, if original appearance isn't a concern, the stainless steel braided flexible brake lines (e.g., those sold by Vette Brakes and Products) are a good upgrade.

-Noel