Issues After Hydroboost Swap

[Supercharged111]

Depends on which seal is leaking. If it's the output seal or football seal those are easy, and hour or 2 and done. Just don't tear the seal like I did. $20 for the kit I think from A Team on Ebay.

 

[Schurkey]

Cast-iron master cylinders are easy to rebuild. The seal kit costs a good share of what a rebuilt master cylinder costs, and the parts kit doesn't have a warranty. There's little savings in rebuilding your own cylinder compared to getting a "rebuilt".

Aluminum master cylinders should not be honed. You'd destroy the hard coating in the cylinder bore. So if the cylinder bore isn't PERFECT--no corrosion, no wear-spots, no wavyness to the bore walls--you're going to waste the money you spent on the seal kit.

In addition, if you happened to have a Quick Take-Up master, you'd have to assure that the pressure-relief valve in the rear reservoir is working properly, bypassing at the correct pressure.



I don't know what an "ABS bypass valve" is.

 

[Jesse_Wenting]

In addition, if you happened to have a Quick Take-Up master, you'd have to assure that the pressure-relief valve in the rear reservoir is working properly, bypassing at the correct pressure.

I didn't think the Hydroboost was ever paired with Quick Take-up MCs, or even compatible with any for that matter? I did consider the possibility that one or both of the remanufactured callipers I used could be Quick Take-up though, but if that were the case I don't understand how I could have had a good pedal feel immediately after the swap from vacuum.

Admittedly I don't understand much about the actual valve function differs in each style of MC. I do know the Quick Take-up has a higher initial volume of fluid

I don't know what an "ABS bypass valve" is.

I don't actually know if that's what I'm feeling, more of an educated guess.

When the pedal is about 3/4 the way to the floor there's a noticeable "click" in the pedal as it travels maybe 1/4 an inch with 0 resistance before regaining pressure. When this happens the brake warning dash light comes on (same one as when you have the park brake engaged) and there is immediately more pressure at the brakes.

This is why I was so convinced my issue was air in the ABS system. Once I'm moving again I can tap the brakes again lightly, I'll feel the same "click" in the pedal, and the brake warning light will turn off. There is noticeably more braking pressure when the dash light is illuminated, but by the time it comes on the pedal is so far through its travel there's practically no boost left

 

[Jesse_Wenting]

Thought I'd give an update to help anyone experiencing this issue in the future. The culprit was indeed the master cylinder, specifically a worn seal in the front piston.

Very easy replacement. Didn't even bleed the lines between the cylinder and the ABS until (I know I should've). Bled the unit in the vehicle with some rubber lines

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It really baffles me that we can't purchase seal kits for master cylinders anymore. A 25¢ piece of rubber cost me a little over $100 in parts.