Bad master cylinder?

[bigjae46]

No way!! A buddy of mine in Texas knows I have an e46 and sent me this photo the other day. I knew it had to be a forum member! Small world!

I was wondering where you got that pic. Yea...small world! Lol


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[eacmen]

You’ll need 2 fittings to screw into the brake line ports to bench bleed the master cylinder. Not sure if a regular brake caliper bleeder screw will work. Put the master cylinder in a vise and then run hose from the ports back to the reservoir. And then fill and them pump the piston with your hand.

Install the master cylinder. Bleed in the system, actuate the ABS pump and bleed some more.

I used Walmart DOT 4 and once everything was good bled Motul into the system, actuated the ABS pump, bled some more.


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Did you use a pressure blender or two person?

How much total fluid did you need to push through the system before it was bled?

Crack the bleeders while actuating the ABS pump?

[SteelGreyM]

It is


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No way!! A buddy of mine in Texas knows I have an e46 and sent me this photo the other day. I knew it had to be a forum member! Small world!

[bigjae46]

Dude is this your car??

It is


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[SteelGreyM]

You’ll need 2 fittings to screw into the brake line ports to bench bleed the master cylinder. Not sure if a regular brake caliper bleeder screw will work. Put the master cylinder in a vise and then run hose from the ports back to the reservoir. And then fill and them pump the piston with your hand.

Install the master cylinder. Bleed in the system, actuate the ABS pump and bleed some more.

I used Walmart DOT 4 and once everything was good bled Motul into the system, actuated the ABS pump, bled some more.


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Dude is this your car??

[bigjae46]

Will do. Starting to understand where “break my wallet” comes from...

Will do. Starting to understand where “break my wallet” comes from...

You’ll need 2 fittings to screw into the brake line ports to bench bleed the master cylinder. Not sure if a regular brake caliper bleeder screw will work. Put the master cylinder in a vise and then run hose from the ports back to the reservoir. And then fill and them pump the piston with your hand.

Install the master cylinder. Bleed in the system, actuate the ABS pump and bleed some more.

I used Walmart DOT 4 and once everything was good bled Motul into the system, actuated the ABS pump, bled some more.


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[SteelGreyM]

Yeah its really annoying ATE doesnt sell this in the aftermarket.

Let me know if it works for you op.

Will do. Starting to understand where “break my wallet” comes from...

[eacmen]

Ordered the MC. Still in disbelief. Will update in a week

Yeah its really annoying ATE doesnt sell this in the aftermarket.

Let me know if it works for you op.

[SteelGreyM]

Ordered the MC. Still in disbelief. Will update in a week

[bigjae46]

Its either air in the brake lines or a bad MC.

[eacmen]

Just “for fun” (I totally didn’t forget to reconnect it) today i disconnected the vac hose going to the brake booster.

The pedal got super hard and the engine had erratic and lagging throttle response.

tl:dr a vac leak that affects the brake booster should be very noticeable!

[eacmen]

I re-read this and the idea of a potential vacuum leak has me thinking...

Where could this leak that effects the braking system be coming from?


The only thing I could think of is maybe this little hose that attaches to the air rail could have unattached without me noticing. I’ll have to check when I get home.

I am just in disbelief that the MC failed this badly this quickly. The more I think about it seems like a vacuum leak.

Then again, with the engine off the brake pedal goes to the floor easily... so probably not vacuum leak right?

Based on that statement its not a vacuum leak. But if there was one it really could be anywhere.

Only thing i can think of is that the brake fluid that was in there was old and caused the seals to degrade while the car was sitting.

[SteelGreyM]

1. Check for fluid on the ground and around the seals between the brake fluid reservoir and the MC.
2. To see if the MC is bad, with the engine off press the brake pedal a few times to remove the vacuum from the booster. Then apply constant pressure to the pedal. If the pedal continues to the floor with constant pressure applied then the MC is bad and needs to be replaced.

My gut is telling me that you just need to bleed the system or there is some intermittent vacuum leak that is affecting the brake booster performance. But I would think you'd be getting a lean condition if you had a vac leak.

I re-read this and the idea of a potential vacuum leak has me thinking...

Where could this leak that effects the braking system be coming from?


The only thing I could think of is maybe this little hose that attaches to the air rail could have unattached without me noticing. I’ll have to check when I get home.

I am just in disbelief that the MC failed this badly this quickly. The more I think about it seems like a vacuum leak.

Then again, with the engine off the brake pedal goes to the floor easily... so probably not vacuum leak right?

[SteelGreyM]

Will bleed the system on Sunday. Thanks for the tips guys. Hoping it’s just some stray air.

[liam821]

Yeah, I would bleed the system again. It took me a few times to get all the air out. Use a power bleeder too, it's a big help.