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Old 08-01-2008, 07:14 PM   #1
z28fan
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74 vette brakes go to floor - car dangerous to drive

just got a 74 vette

Runs and drives good

BRakes have a problem - pedal goes to the floor

Supposedly, new master cylinder - it doens't look to old, brake fluid in it is clean , supposedly had a new caliper on the rear too. Don't know for sure what is new since I just got the car last night.

He told me that the brakes needed bleeding. I tried to bleed them - and had no luck. Are these hard to bleed and is there a special trick to them?

Why would the brakes go to the floor? Don't see a leak, the master cylinder seems to stay full and the brake light does not come on.

Help please
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Old 08-01-2008, 08:02 PM   #2
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First, DO NOT DRIVE THE CAR.(Had to say it,sorry)

Second. I suspect more issues.

Third. Get a friend to help you, or get 6 speed bleeders at Autozone, or better yet, buy a Motive pressure bleeder.
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Old 08-01-2008, 08:10 PM   #3
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Is there more than one bleeder on the calipers?

Any trick to bleeding these things?

What other problems you think there could be with it?
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Old 08-01-2008, 08:28 PM   #4
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Quote:
Originally Posted by z28fan View Post
Is there more than one bleeder on the calipers?

Any trick to bleeding these things?

What other problems you think there could be with it?
Fronts have 1 each. Rears have 2. If you have ever bled brakes, nothing special.

If there is air in there, it got in there somehow..................
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Old 08-01-2008, 08:35 PM   #5
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So where are the two on the rear calipers? I found the one up in the front near the top. They are hard to get at with the tires.

I think if there is air in there it happened when he changed the Master cylinder.
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Old 08-01-2008, 09:03 PM   #6
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It could be master cylinder related, Sometimes people forget to bench bleed them before installing.
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Old 08-01-2008, 09:05 PM   #7
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Could be, is there a way to bleed the master?
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Old 08-01-2008, 09:27 PM   #8
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Make sure you bleed the calipers in the write order
Also are the calipers the original caliper if so the old seals might be bad

On my 71 the o ring calipers solved the soft pedal problem
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Old 08-01-2008, 09:29 PM   #9
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O ring caliper? Ar ethese something sifferent than what comes on the car?
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Old 08-01-2008, 09:50 PM   #10
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master should have been benched bled
and to bleed the brakes ITS BEEN A LONG TIME [ but its right rear to front left to left rear to front right sound like a dumb ass way but it works

im sure someone that heard that b4 will please chime in
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Old 08-01-2008, 10:15 PM   #11
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I am to understand that the original calipers came with lip seals
If the car sets for long periods of time the brake pedal will get soft
You can buy oring caliper from most of the corvette venders

Get that motive brake bleeder
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Old 08-01-2008, 10:44 PM   #12
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Quote:
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Could be, is there a way to bleed the master?
The easiest way is in a vice. You buy a length of brake line, cut in half, and bend them so that the out lines curve up and into the reservoir. You then pump it till it runs clear, then install it.
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Old 08-01-2008, 10:48 PM   #13
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Quote:
Originally Posted by bojvette View Post
master should have been benched bled
and to bleed the brakes ITS BEEN A LONG TIME [ but its right rear to front left to left rear to front right sound like a dumb ass way but it works

im sure someone that heard that b4 will please chime in
The books say furthest from the master, working toward the closest.
The GM books from the 30's say to do the closest, then work towards the furthest
I imagine it just doesn't matter.
GM manuals of the day recommend power bleeding. I would bet that is more about saving shop time more than anything. It IS the fastest, and most thorough, since you expell and change the fluid.
Being hydroscopic, it's best to do it anyways every other year.
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Old 08-02-2008, 09:50 AM   #14
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I agree that the Motive Bleeder is a GREAT investment. For $90 it's well worth it. (http://store.summitracing.com/partde...5&autoview=sku)


One tip when using it: get a 4" or 6" C-clamp and use that to hold the plate on top of the master cylinder. The chains and hooks never worked too well for me.

Can you ask the guy when the problem started and if it got worse or better after he replaced the MC? It's tough to narrow down the source without more info.

Do you notice any fluid around dripping on your wheels or splashed on the underside of your fenders? If your lip seals are bad (they get flat spots from sitting for extended periods) then you should see evidence of leaks. Especially if you have no pedal pressure.

Then I'd bleed the MC. Just do a google search and you should find some decent instructions with pics. It will involve disconnecting the hard lines from the MC, so be careful not to spill that brake fluid all over your engine compartment and fenders! Once the MC is bled, move on to the rest of the system. Go in this order: right rear, left rear, right front, left front. Furthest to shortest distance to MC.

Give that a shot and let us know how it works out for you

Oh yeah, and congrats on the new car! We like pics
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Old 08-02-2008, 12:09 PM   #15
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Since you don't who worked on the car in the past or what was really done to it I suggest you start from the beginning.
First be sure you have the correct M/C. The bores are different between manual and PB cars. Take off the cover and look at the BF, is it clear or muddy? If muddy then you have moisture in your system and it hasn't been worked on in a while.

Remove the M/C and bench bleed it. The best way is to go to NAPA with it and get the metric steel line conversions. The tapped hole are 2 different sizes. Once you the line with the correct flared nut, cut the other end off and bend them up into the chambers so you can bleed the M/C with a plunger,screwdriver,punch etc.


Lip seal calipers are fine to use and once the system is setup correctly will work for years. Be sure the calipers are in good shape, just because they may be SS lines doesn't mean they won't lock up with bad BF. You may want to get a seal kit and open them up and clean them out with CLEAN dot3 BF. You don't need DOT 4 or 5, 3 will work you just need to bleed the system if you store the car for a few months.

Now check your rubber hoses, if they are older then 5 years or you don't know, replace them.

Look at the rotors, mic them. They should be in the 1.215- 1.250 range. I toss them if they are under 1.225" Do they have the rivets in them? If so that's good no one was in there. If they're gone then who know what hack laid his hands on them.Check the rotor runout and bearing endpay both should be under 003" If you need rotors you do NOT need slotted and drilled rotors, send me your cash if you want to throw it away. I use both USA and imported rotors with the rivet holes,not all have them. I hate imports but the ones I used are good and sad to say as good as the USA rotors. Do not expect new rotors to dial in without help. Some may but most will be out. I've found both import and USA out as much as 012. This is where someplaces will tell you the spindle is bent and you need a new one.

Then assemble with organic pads. You don't need metallics for the street, if you're going to be road racing and laying on the brakes then use the metallics.

If you follow all the above and use the Motive you should have brakes that stop on a dime- just like they did 40 years ago before the hacks started working on them.

Good luck
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