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Discussion Starter #1
Hey everybody,

So I recently got finished with installing all new cobra disk brakes on all four, and also installing a hydro-boost system on my Mk 3. I've bled brakes on my different cars but not one with hydro boost on it. So recently what is happening is that i fill up the reservoir and and start with the passenger rear break since it is furthest away. I'm barely getting any fluid at all and its very inconsistent. So I moved up front and im getting fluid but its not enough pressure to even push the cylinders of the breaks in.

Is there a special process with hydroboost? or is it a possibility my master cylinder is bad.

1997 Cobra brakes
1997 hydroboost
 

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1st RFM/FFR Legacy Winner
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Hydroboost has no effect on the bleeding process.

Greg
 

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Cobra Poor
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You have to bleed the hydroboost first....at least that's what I did. The rest of the bleeding is just like normal.
 

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What do you mean, bleed the hydroboost. Fill the system with hydraulic fluid and turn the PS pump?

Greg
 

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1. fill the reservoir
2. bleed the hydroboost master cylinder same as you would bleed a brake (bleed screw usually on outboard side of MC).
3. then bleed the brakes individually, topping off reservoir at each step.

I kept the ABS from my donor which added a few steps for those who do:
If you have a Ford dealer's computer, they can cycle the solenoids and valves in the ABS pump and bleed it that way. As I am not a Ford dealer, I had to do it the more interesting way. While a go kart, brake multiple times to engage the ABS each time, then bleed the brakes. Then repeat.
Believe me, as light as it is as a kart, need the 5 point harness on very securely or you will be launched over the engine :)>
 

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There is a bleed bolt on top of the HB unit (not on master cylinder) but I never used it. I bled brakes normally with engine off and the HB bled itself with the engine running. It should cycle the air out just like the power steering rack does.
 

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Is it a new M/C or an old one from a donor?

Do yourself a favor, don't do as I did!
For anyone building a car, DO NOT PUT OLD PARTS on your new car! When I built mine, I installed new brake-lines, new fittings, new braided/flex lines, and turned in my old parts as cores and got new calipers, new rotors, and new booster. The ONLY thing I didn't replace was the Master Cylinder. I thought about it at the time, but decided to save the $100. DUMB DUMB DUMB. Don't do it!
Do it before the body goes on! :yes:

First Trailer ride!
:blink:
 

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I kept the ABS from my donor which added a few steps for those who do:
If you have a Ford dealer's computer, they can cycle the solenoids and valves in the ABS pump and bleed it that way. As I am not a Ford dealer, I had to do it the more interesting way. While a go kart, brake multiple times to engage the ABS each time, then bleed the brakes. Then repeat.
Believe me, as light as it is as a kart, need the 5 point harness on very securely or you will be launched over the engine :)>
To clarify, ABS has no effect on the brake bleeding process if you use the 94-95 controller. For controllers made at some point after 1995, heartstarter is correct.

Greg
 

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There is a bleed bolt on top of the HB unit (not on master cylinder) but I never used it.
You need to leave that one alone unless you have the tool setup for that.

As stated before the Hydro boost bleeding procedure is the same as on most vehicles.

Good luck and have fun.
:wrench::wrench::wrench:
 

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Discussion Starter #11
to clarify, i already have the powersteering/hydroboost bleed and it good to go. but the problems that i am having is that, i have my master cylinder filled up. and i started with the furthest tire. but i cant seem to get any significant pressure to build up anywhere.

Im using a fox pedal box, does the plunger that is attached to the break need to be modified or lengthened?
 

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to clarify, i already have the powersteering/hydroboost bleed and it good to go. but the problems that i am having is that, i have my master cylinder filled up. and i started with the furthest tire. but i cant seem to get any significant pressure to build up anywhere.

Im using a fox pedal box, does the plunger that is attached to the break need to be modified or lengthened?
MOST people utilizing hydroboost start with an SN-95 pedal box and a hydroboost specific pedal fits best of the pedal choices available.

Have you eyeballed the pushrod movement to see if it is straight and not bound up on something preventing it from pressurizing the MC? It doesn't take much misalignment to cause a problem here.

Sean
 
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