No Brake Pedal

[vetteboy86]

First let me tell you that this is a friends 72 without power brakes. We were told that it had stainless calipers. There is no pedal at all, even when they are pumped rapidly. The fluid looked a little cloudy.

I thought bleeding them would make a noticeable difference but it didn't. I got good fluid flow from all four calipers. I started at the right rear, then the left rear, then the right front then the left front. Good flow out of all of them.

I told him to buy a master cylinder. I blead the master cylinder prior to putting it on the car until no air bubbles were present. Put the master cylinder on the car, re-blead the brakes, and there is no change in the resistance of the pedal. I am getting good fluid flow once again. What else is there? I dont see any leaky calipers! Does the proportioning valve have anything to do with brake pedal resistance? Or do I need to bleed them a whole lot more?

On the initial bleed, The first few times I opened each bleeder a little air came out but we kept going until it was steady fluid. Maybe we didn't bleed enough fluid the second time through, as I would assume the air now is right at the master cylinder and would need to be pushed all the way through the lines.

Thanks,
Craig

 

[vetteboy86]

Okay, so I did some research into this issue and found some interesting things out. I should have done this before posting, but I was in a hurry!

I didn't know that the rears had two bleeders. I only knew of the ones located on the top of the caliper. I will bleed the brakes once again tomorrow and bleed at these bleeders as well. Can someone confirm the sequence of bleeding the two bleeders on each of the rear calipers?

Also, I stumbled across the run out problem with these cars. I don't believe this to be my issue, not yet at least. As that problem tends to give good pedal for a few miles then as more air is sucked in the worse the pedal gets.

 

[minifridge1138]

Well my 1982 actually has 3 bleeders on the rear. 1 inner and 2 outer.

The shop manual specifies this bleed order:

Left Rear Inner, Left Rear Outer.
Right Rear Inner, Right Rear Outer.
Left front.
Right front.

I was surprised when it had me do the left first, but I did as it recommended.

Good Luck!

 

[6880 Mike]

Your recurring brake problems are most likely leaking calipers (check all four regardless of whether you see any brake fluid on the ground) or rotor run out. Check the run out on all four corners.

 

[vetteboy86]

I came across the rotor run out idea while I was searching. However in those cases, the symptoms were momentary brake pedal, for 50 or so miles of driving. In my case I don't have pedal regardless of bleeding them.

From my reading I believe the run out occurs as you drive the vehicle, where the piston travels with the disc. Due to differences in the surface of the disc, and disc thickness, the piston turns into an air pump moving in and out which results in sucking air past the seals, and not allowing fluid the other way. Is this a fair description of run out? This may be a problem with this car, but I cannot confirm that yet because I don't have any brake pedal after bleeding with the car on jackstands sitting stationary.

I'm having a hard time believing that bleeding the other two bleeders on the rears will make that much difference.

 

[LVMYVT76]

You can go to CORVETTE MAGAZINE.COM, look up brake overhaul, there is more information than you you need at first in the article, but towards the end it tells how to bleed the new master cyclinder and brakes. If youare bleeding the brakes, get all the old fluid out until new fluid comes out. Good luck.

 

[vetteboy86]

Thanks

 

[petes74ttop]

I'm having a hard time believing that bleeding the other two bleeders on the rears will make that much difference.[/quote]

Yes it will make a difference, you have to bleed both the inner and outers. PG.

 

[vetteboy86]

Yep, I was 100% wrong. After bleeding the inners and outers correctly we now have good pedal. I guess the next step is to see how long it lasts. Thanks for all the help.

 

[6880 Mike]

Yep, I was 100% wrong. After bleeding the inners and outers correctly we now have good pedal. I guess the next step is to see how long it lasts. Thanks for all the help.

Wouldn't hurt to check run out while you've got the wheels off.

 

[White75]

I'm having a hard time believing that bleeding the other two bleeders on the rears will make that much difference.

Yes it will make a difference, you have to bleed both the inner and outers. PG.[/quote]
If memory serves me right, the other single bleeder is so that calipers could be used on either side of the car. simply replace the brake line with the bleeder.