Hey I have a 68 Camaro with a brand new zz383 motor, th350 AT, edelbrock rpm air gap manifold, and 750 VS speed demon. The car has 4 wheel wilwood disc brakes with wilwood calipers and braided brake lines. The booster appears to be a 7 or 8 inch dual diaphragm, and the proportioning valve is the correct one.

Most of the time, the brake assist from the booster is there, but it is definately lacking. It is not as hard to depress the brakes as when the car is off and the assist has been used up, but there is definately too much effort imo. At one point in time, I randomly started the car and for that day there was plenty of brake assist, comparable to a modern car. Now, especially when the car warms up, the brakes are a pain to push, but I know there is some assist there because the pedal is not rock hard.

I'm looking for some suggestions to fix this problem. I already took the check valve out and it seems to work properly, the booster line goes from the check valve to a brass 90 degree fitting on the intake manifold. The line is brand new and is not cracking. When i move the check valve around in the booster, air hisses so there is SOME vacuum in the system.

Any suggestions would be greatly appreciated.

Thanks, Matt

When i move the check valve around in the booster, air hisses so there is SOME vacuum in the system.





This statement leads me to believe that it's NOT a power booster issue!:noway:.....It's either a restricted brake line or hose or a bad caliper!:yes:

This statement leads me to believe that it's NOT a power booster issue!:noway:.....It's either a restricted brake line or hose or a bad caliper!:yes:

What would be the procedure to troubleshoot it?

Is the pushrod clevis pin positioned in the lower pedal hole? Is the rear center hose new too? They tend to clog over time.

Hey I have a 68 Camaro with a brand new zz383 motor, th350 AT, edelbrock rpm air gap manifold, and 750 VS speed demon. The car has 4 wheel wilwood disc brakes with wilwood calipers and braided brake lines. The booster appears to be a 7 or 8 inch dual diaphragm, and the proportioning valve is the correct one.

Most of the time, the brake assist from the booster is there, but it is definately lacking. It is not as hard to depress the brakes as when the car is off and the assist has been used up, but there is definately too much effort imo. At one point in time, I randomly started the car and for that day there was plenty of brake assist, comparable to a modern car. Now, especially when the car warms up, the brakes are a pain to push, but I know there is some assist there because the pedal is not rock hard.

I'm looking for some suggestions to fix this problem. I already took the check valve out and it seems to work properly, the booster line goes from the check valve to a brass 90 degree fitting on the intake manifold. The line is brand new and is not cracking. When i move the check valve around in the booster, air hisses so there is SOME vacuum in the system.

Any suggestions would be greatly appreciated.

Thanks, Matt

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I would make sure you have the correct bore master clyinder for Wilwood brakes with booster. I would call Wilwood and see what they recommend. I went thru this same issue with Baer brakes and a Wilwood master cylinder. Come to find out it was the master cylinder bore was to big. My problems was it would run thru the brakes. If I pressed real hard they would work fine.

The thing is, the brakes HAVE worked properly before. There are times where they will temporarily be very easy to depress, and have a very good pedal feel. But most of the time, the pedal feels tough, mushy, etc, though with some assist from the booster because the pedal is not AS hard as with the car off and the booster bled.

Also, the pedal return when releasing the brake is slow and mushy. Furthermore, cruising down hills at ~50mph, 1500-1700 rpm closed throttle, the brakes will be tougher than usual, and will not have that much stopping power.

I did not replace the brake hardlines, only the flexlines, I will also double check on the rear-end flex line to see if its new or old.

Is the pushrod clevis pin positioned in the lower pedal hole? Is the rear center hose new too? They tend to clog over time.

I checked over the rear-end of the car today. Interestingly enough I found what I believe is an axle leak; the brake caliper and pads, the inner side of the wheel, and the inner part of the rotor (the hub, not the rubbing surface) are covered in dirty black grease.

Also, the flex-line which connects the body hardline to the rear-end is original. Should I replace it with a braided flexline? Furthermore, most of the hardlines are original, should I replace them as well?

P.S. yes the pushrod clevis pin is in the lower hole.

Thanks for the help,
Matt

I've heard of brakes locking up due to a bad rubber line, and I suppose brake apply problems could result as well. I imagine what is happening is that the inner liner of the rubber line tears loose and acts like a check valve in the line preventing fluid from flowing into or out of the caliper. So it would be a good idea to replace them if they're suspect.

My first thought on this was to ask "what is your idle vacuum reading"?

Just for grins.... measure your vacuum.... I would guess its low and not enough.

I've heard of brakes locking up due to a bad rubber line, and I suppose brake apply problems could result as well. I imagine what is happening is that the inner liner of the rubber line tears loose and acts like a check valve in the line preventing fluid from flowing into or out of the caliper. So it would be a good idea to replace them if they're suspect.

My first thought on this was to ask "what is your idle vacuum reading"?

Idling - Out of gear 15-16 in/lbs

In Gear 13-13.5 in/lbs

Like I said before, the brake assist does work and HAS worked well in the past, just it is very inconsistent. Especially down a long descent/grade (speed approx. 55-60 mph), I press the brakes and there is not much booster power (shouldn't this be where vacuum is highest? - 2000rpm cruise downhill throttle shut). The pedal return is slow and unsatisfactory.