Hydra Boost help needed!
 

Quick run down, 1967 GTO all new brake parts, wilwood discs all 4 corners, 6 piston front, 4 piston rear, CPP Show Stopper hydra boost, their master and proportioning valve. March style track pulley system, type 2 PS Pump that came with kit.
System has been working perfect for months with minimal driving (<40 miles) but lots of starting, stopping and moving the vehicle. Again, has been perfect.
Took it to the alignment shop today for the initial alignment. Afterwards I have no brake pedal. Every 8th or 9th stop I’ll get a firm pedal. Went through the outlined Hydra Boost bleeding procedure again with no change. I watched the alignment being done and the tech used a rod to hold the pedal down while rotating the steering wheel to check caster etc. My guess is I got an air bubble in the accumulator. I have no whine, pulsing or indication of a slipping belt. Fluid level in the PS and brake system are still topped of with no micro bubbles in the PS fluid. The pedal will not pump up like there is air in the brake system. There are brakes at the very bottom. The PS reservoir is the PSC canister in the pic.

Pic included for reference.
Help?

Quite possible you have air in the brake system, not the hydra boost. Possibly have small leak somewhere and with brake pedal depressor on it lost some fluid and sucked in some air?
Love the reservoir on that system.

Thanks for the reply. I just bled the brake system again and got no air. And the peddle got slightly better. But, it will not hold pressure. 5 or 6 pumps of the peddle brings pressure to the top, then it bleeds right off. No visible leaks anywhere. Keep in mind this system has been fully functional for nearly a year. Still scratching my head. Going to start at the master and bleed again. Could be sticky piston or proportioning valve.

Another thing to try is light clamp off the flex hose, one wheel at a time, then try pedal.
might give you an area to start with.

Tried that, steel braided, won’t clamp tight. I have a brake tech stopping by shortly, I’ll let you know what we do or don’t find.

Ya the stainless lines won't clamp.
What type of P/s pump are you using, small style with no reservoir? Nothing to do with brakes pedal, just interested in the
pump and reservoir. Have Hybraboost on my 64, but using pump with reservoir and T on return line. Not happy with T.

Don't shoot me on this picture, LOL. Yes it has a SBC in it. Been harassed already about it. It's a Canadian Pontiac Motor, LOL. Just a pic of the booster system.

Sounds like the master went bad

Yes, the pump is one of the type 2 pumps. What I really liked about the reservoir is that both return lines connect independently. Then the return to the pump is the third. I can get part #s if needed.

That’s exactly what my tech buddy told me. I just finished pulling and disassembling. Only thing I found was a nick in the forward most seal/cup. It almost looks like a factory notch.

In the pics the close up of the secondary piston you can see the notch. The other pic shows the orientation they came out. Would a blown seal in this area cause my symptoms?

Ya kinda figured it would be that style pump, Mine is a whole different aftermarket set up so will have to figure something out. works ok for now.
That front seal really doesn't look right. But haven't and one of those apart for years. Might want to send CPP a picture and ask them if this is right.

I had a second return nipple added to my reservoir years ago vs using the "T" in the return line to the reservoir. Now I see that I made the right decision.

Tom V.

Front half of the master cylinder won't make/build pressure with that cup damaged..

That nick ain't factory. It's a busted cup.

Better check the bore good.
Clay

When I put my hydroboost system on (with a CPP master), I had tons of problems - brakes failing, etc. After tons of troubleshooting, I gave up and took the car to a mechanic. After tons more troubleshooting, he took the master cylinder apart, and found that it had been assembled with the wrong parts. (I forget the details.) I would have never figured it out, but he is a CPP dealer and spotted it right away.

CPP Master rebuild.
 

Thanks again for the replies.
I’m glad that we determined the “notch” to be the smoking gun. My brake tech told me the master looked like the 68-76 Corvette. After looking for a rebuild kit online, I confirmed his guess. No luck finding a kit locally. Amazon lists one for 66 bucks, but delayed till next month because of prioritization of orders. Summit listed one also but still Wednesday before I could get it.
My local Napa had a brand new MC on the shelf for 50 bucks. Has the same bore size (1 1/8 inch) so I took a chance. Upon disassembly, it’s a prefect match with one exception, it is designed for the deep bore on the pushrod end. The CPP unit is too, but comes with a metal “piston” to make it a shallow bore. The new unit from Napa has too small of a bore on the pushrod end to use the piston. I have access to a lathe that I could use to open the bore or turn down the piston. In the end I decided it wasn’t worth it. I plan on either reusing the primary piston from the CPP unit as is or swap the cups onto it from the new unit. Stay tuned.

In the pics the parts on the right are from the new MC. I’d use calipers to measure difference in the bore diameter, but they’re in storage out of state.

Success!!!
Aside from a little scuffing, the bore looked brand new. Using the new secondary piston with cup and the primary piston from the CPP unit, brakes are outstanding. I tried to remove the cups from the new units primary piston. I wasn’t confident in being able to replace all the cups without damaging them. As the cups from the CPP unit were still in good shape, I reused the entire primary assembly. If I ever have to do this again, I will turn down the small piston that goes in the rod end so all of the guts from the 68-76 Corvette unit can be installed in the CPP master.

Hope this is informative for someone down the road ��