Bad master cylinder?

[Kdubski]

Have the exact same problem after an engine rebuild. The air in MC noise appeared 300 miles after putting motor in. Dealt with it during break in and now that spring is here going to look into it.

Could it just be a coincidence or maybe assembly error?

[SteelGreyM]

Ok so update.

I’ve been driving the car around for a week now. Put 2xx miles on it. The brake pedal is hard as a rock with the engine off. Engine on the brake pedal is firm 50% of the way through.

I literally haven’t even touched the braking system as my master cylinder just arrived.

Sooo am I looking at air in the lines or do I still need to swap that thing out.

[eacmen]

Ok so update.

I’ve been driving the car around for a week now. Put 2xx miles on it. The brake pedal is hard as a rock with the engine off. Engine on the brake pedal is firm 50% of the way through.

I literally haven’t even touched the braking system as my master cylinder just arrived.

Sooo am I looking at air in the lines or do I still need to swap that thing out.

So with the engine on the brake pedal is firm for the first half of the pedal travel then gets soft?

I think this is due to the vac assist. With the engine off you can’t apply enough force to cause the pedal to go soft.

[SteelGreyM]

So with the engine on the brake pedal is firm for the first half of the pedal travel then gets soft?

I think this is due to the vac assist. With the engine off you can’t apply enough force to cause the pedal to go soft.

Other way around!

The first half is soft then it firms up. Like it needs a really good bleeding! I think you guys may have been right about air in the lines. Still unsure how on earth it got there as I didn’t touch the braking system... but now I’m motivated to do a bleeding (something I should’ve done to begin with).

[eacmen]

Other way around!

The first half is soft then it firms up. Like it needs a really good bleeding! I think you guys may have been right about air in the lines. Still unsure how on earth it got there as I didn’t touch the braking system... but now I’m motivated to do a bleeding (something I should’ve done to begin with).

Yeah bleeding it to see what happens is way cheaper than the $600 MC!

If with the engine off the pedal gets firm and you can keep constant pressure and the pedal does not sink then the MC is okay.

Soft pedal at beginning of travel is air.

[eacmen]

FYI If you end up not installing the MC may want to hold onto it as they are hard to find right now.

[Kdubski]

Any update?

[Kdubski]

bump

[Kdubski]

https://www.youtube.com/watch?v=Knguw0Bdt8c

[SteelGreyM]

Any update?

Hey sorry. Not super active. I never changed my cylinder out as my brakes magically fixed themselves. Your video sounds like air leaking past the brake booster but get a second opinion for sure. I did end up buying a used MC + brake booster with 80k miles if you want. I have no use for it anymore.

[Kdubski]

Update.... replaced MC & Booster... sound returned roughly 250 miles following install, same way it originally came on. Anyone else deal with a brake/MC issue following engine rebuild/install?

[bigjae46]

That sounds weird. Are you sure the check valve and solenoid are in good shape and not leaking?


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[eacmen]

Update.... replaced MC & Booster... sound returned roughly 250 miles following install, same way it originally came on. Anyone else deal with a brake/MC issue following engine rebuild/install?

Sound happens no matter how many times you pump the pedal with engine off?

Would recommend checking for vac leak before and after check valve. Smoke test it.

[Kdubski]

Sound happens no matter how many times you pump the pedal with engine off?

Would recommend checking for vac leak before and after check valve. Smoke test it.

With engine off sound happens until pedal firms up. It doesn't happen with light smooth braking, it happens with heavier pedal pressure. I.e) pump the pedal fast a few times.

Smoke test was clean!

[Kdubski]

That sounds weird. Are you sure the check valve and solenoid are in good shape and not leaking?


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Ill add that to the list of things to check. One thing I noticed is that the brake fluid gets unbelievably dirty quickly in the MC reservoir.