stuck hydrobooster

[Pirana]

I've been busy for two evenings now trying to locate a problem with a hydroboost brake system.
A friend of mine bought a '70 1/2 camaro wich is totally restored.

Beatiful car ,......but it also had the stock mastercilinder without booster.
So we updated it to a hydroboost system from a late 90's astro van,complete with mastercilinder.

At first it performed flawlessly,with good braking,but after some 100 miles he complained about the brakes not getting loose after braking.
I've driven the car two days ago and it feels like some residual pressure.
After braking it takes a second or two to come loose,it just like your still braking a little.
There's no difference in normal or hard braking when it occurs.
We've taken of the master and cleaned it,put another (slighly heavier)spring in the hydroboost to help the rod inside get back a little,but no succes.
Braking with your right foot and immediatly helping it upwards with your left helps a little,but not as expected.
The only thing not used from the astro van was the prop valve,but we still have it.

Any comments on this problem?


thanks,Louis

[6'9"Witha69]

Did the Astro Vans have the QTU (Quick take up) which steps the release of pressure? I can't remember off hand.

Is there a return spring on the pedal? There should be.

[CarlC]

How are your return lines routed for both the booster and box? If a "T" is used near the box there is a chance the booster will experience a pressure feedback through the return line. This feedback through the booster return line will lightly apply the brakes. Start the engine, apply the brake by hand, release, then rev the engine. Watch the brake pedal and rod to see if they move. The higher the engine speed, the more fluid is moved, the greater the feedback, the more the pedal moves.

Re-routing the booster return line close to the PS reservoir or cooler will fix the problem.

[terryr]

The return line from the hydroboost has a restriction in it that slows down the release. I've been fiddling with mine.

http://members.shaw.ca/pekpress/HydroboostSwap.html

[Pirana]

Thanks guys,i had some ideas that are the same as mentioned.

there is no T in the return line,both hydroboost and steering have their own return.
Only the hydroboost and mastercil. were purchased,there were no lines with it.
We tried a return spring on the pedal and this helps quit a lot!
Adding a bigger return is one option were gonna try...

I don't know if it has the QTU...

[79T/Aman]

well GM started using QTU masters in 81 if I recall, at least on the F-bodies, and the calipers have to match the QTU master this was one of those things the factory came up with to reduce drag and improve fuel economy.

[6'9"Witha69]

well GM started using QTU masters in 81 if I recall, at least on the F-bodies, and the calipers have to match the QTU master this was one of those things the factory came up with to reduce drag and improve fuel economy.Yeah, I was thinking he may have a mismatch b/e MC and Calipers if it was a QTU MC.


Glad to hear the pedal return helped out.