Have you ever tried to replace a MC without bench bleeding and see how it goes.

Well here is my experience.

1. Remove all brake fluid from MC
2. Remove brake lines from MC
3. Plug brake lines to prevent fluid leaking on to car.
4. Remove MC from car.
5. My MC is a wilwood (260-8556) failure leaking from push rod location.
6. Check push rod lenght dimensions.
7. Install New wilwood MC
8. Connect lines to MC.
9. Fill MC front and rear reservoir.

So here is the big first step.

1. Lift the back of the car until the level of the master cylinder is where the front the MC is lower than the rear of the MC.


2. Then I bleed the MC to remove air following my proceedure I always use when changing / bleeding brake fluid.
https://www.corvetteforum.com/forums...-cylinder.html

3. Well doing this without blench bleeding was like bench bleeding while on the car. A lot of air is bled via the bleed holes in the bottom of the MC.

4. once no air is coming out of the bleed holes, then I do a pressure bleed via the calipers. This removed the air introduced in the lines from removing the brake lines.



Well results where 100% sucess. Brakes where rock solid. Went to the road course track a week later, and brakes where the same as before.

So overall I was 100% happy trying this. No messy brake fluid experience at all. Every step was nice and clean.

Now without bleeding the MC FIRST THIS WOULD BE A FAILURE.

Yes you can bench bleed first (Messy) but you will still need to bleed the MC while on the car. So skipping the bench bleed step on my MC didn't affect the end result.

 

I think your first step is the most important - the rear of the MC must be higher than the front. I suspect many folks don't realize the air trap the standard mounting creates at the front of the bore. I have used this technique ever since I read it here - probably one of your posts years ago - thank you!

 

I bench bleed on the car. Use the hoses and fittings in the kit.Small half stokes on the brake pedal being careful not to bury my foot in the pump and break the shaft seal. I have never jacked up a car and have done this many times. Firm pedal, no air every time. Just done a friends 77 corvette.

 

Well without getting the MC in the proper level there will always be trapped air. Doesn't mean the pedal isn't firm, (This depends on a person's impression of firm) when you drive your car for track days every little bit of air makes a big difference as the brakes heat up.
When its trapped at the MC piston bore it never bleeds via the calipers. You always trap air disconnecting the MC Bleeding kit and adding brake lines. This air usually makes it to the MC Bore piston area.

Only way to remove this air is

Bleed the MC in the correct level

or drive down a very steep hill slowly braking / release.

But try it after you do your bench bleed on the car, lift the car and you will a few more bubbles from the MC Bleed holes.

 

Probably, I wouldn't attempt to replace a MC on a a steep incline or decline anyway. I'm OCD about brakes. Can't stand a spongy pedal. Mine stops on a dime as all my cars have but I'll try it next time.

 

This was super helpful. The brakes are bled, but I still had a slightly soft pedal. I slow down great from say 45mph down to 5mph, but the full stop I need to push hard.

I lifted the front up as mentioned. Hit the brake lightly. The front reservoir shot right out, and the rear reservoir did nothing. Not even bubbles. Of course, I did this in my work cloths as I was walking out the door this morning, but I have a starting point after work tonight. Going to assume it is plugged first.

 

Yup, no problem bleeding the master cylinder in the car. I just pulled the car down my driveway (I live on the side of a hill) until the top of the master cylinder was tipped to the front using a spirit level just like you show. I did tap the side of the master cylinder with a plastic hammer to make sure the last bubble of air was out.

JT