Hydroboost brake bleeding?

[brian1115]

I replaced the Brake booster in my truck with a hydroboost unit. The master cylinder is brand new and the proportioning valve is a wilwood valve. The master cylinder is bench bled correctly.

I have bled all the brakes and the pedal still feels a little spongy. If I pump the pedal about 4 times it stiffens up. The truck is not running yet and I am wondering if this is normal for a hydroboost.


Does the pedal feel stiffer with a vacuum booster vs a hydroboost unit? Will turning on the engine and having power steering fluid go to the hydroboost affect pedal stiffness?

If anyone that swapped to hydroboost can chime in that would be great thanks.

[sweetk30]

hydroboost not running or the 2-3 extra pumps stored used up do feel weird .

fire it for a little bit and check pedal . but also they will let you push way down past whats needed as hydroboost has more pressure assist . so you almost need to test drive it in the driveway or parking lot to be 100% sure .

[Corts60]

Originally Posted by brian1115

I replaced the Brake booster in my truck with a hydroboost unit. The master cylinder is brand new and the proportioning valve is a wilwood valve. The master cylinder is bench bled correctly.

I have bled all the brakes and the pedal still feels a little spongy. If I pump the pedal about 4 times it stiffens up. The truck is not running yet and I am wondering if this is normal for a hydroboost.


Does the pedal feel stiffer with a vacuum booster vs a hydroboost unit? Will turning on the engine and having power steering fluid go to the hydroboost affect pedal stiffness?

If anyone that swapped to hydroboost can chime in that would be great thanks.

It will not bleed properly until the power steering pump is running and pumping fluid through it.