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Resolved Can't get brakes to fully bleed after master cylinder install

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dsmcrzy

10+ Year Contributor
1,632
346
Dec 20, 2009
Trenton, Ohio
Hey Guys maybe someone on here can point me in the right direction because I must be missing something.

I bought a new 3g master cylinder from rockauto since my current one was getting bad and I am trying to clean up my engine bay.

So I researched and got all the correct flare to An fittings and decided to switch to ss AN line like Gofer did with his 3g install. I will post some pics of it below.

I bench bleed the master cylinder and then bleed it again on the car before I installed the lines.

Now I have speed bleeders installed on all 4 corners and I have a hand vacuum pump for brake bleeding and I had my gf pumping the brakes for me.

I started at the back passenger side And worked my way closer to the MC just like in the FSM.

Here's the thing though I still don't have any real brake pressure. I bleed and bleed and bleed until there are no more bubbles coming out and then get everything closed up and press the brake and they are mushy until the bottom when they get tight. Now if I go back around I get more sir coming out of the bleeders.

Now I didn't do this once I went around the car at least a dozen times. Clearly something isn't right.

Anyone have any thoughts??

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Solution
Ok so I tried a few things. I got some longer speed bleeders and put some thread sealer on them. I was able to get the system fully bled.

After that my brakes wouldn't fully engage until the pedal was about half way down. I adjusted the linkage as much as I could but came to no success. I ended up buying the 3G 8+9 brake booster. I installed that. Adjusted the linkage and BAM problem solved!

Car is back up and running again. Thanks everyone for the help.
Try using Teflon tape on the bleeder threads.
 
Hey Guys maybe someone on here can point me in the right direction because I must be missing something.

I bought a new 3g master cylinder from rockauto since my current one was getting bad and I am trying to clean up my engine bay.

So I researched and got all the correct flare to An fittings and decided to switch to ss AN line like Gofer did with his 3g install. I will post some pics of it below.

I bench bleed the master cylinder and then bleed it again on the car before I installed the lines.

Now I have speed bleeders installed on all 4 corners and I have a hand vacuum pump for brake bleeding and I had my gf pumping the brakes for me.

I started at the back passenger side And worked my way closer to the MC just like in the FSM.

Here's the thing though I still don't have any real brake pressure. I bleed and bleed and bleed until there are no more bubbles coming out and then get everything closed up and press the brake and they are mushy until the bottom when they get tight. Now if I go back around I get more sir coming out of the bleeders.

Now I didn't do this once I went around the car at least a dozen times. Clearly something isn't right.

Anyone have any thoughts??

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Your brake booster has to biuld pressure before you will have any pressure. You might have air leaking past the check valve.

-Gary
 
Ok I will try that.

The thing that concerns me is that I bleed the system untill I get no more air bubbles coming out. Then I press the brakes to see what kind of pressure I have, which hasn't been good. And then go around to bleed again I get more air coming out.

I just can't see where the air is coming from. There are no leaks at all.
 
A master cylinder can have an internal leak that can add air to the system. In fact, that's what it sounds like in your case. I know it's a new m/c but a new m/c CAN still leak. Even if it isn't leaking internally, air can get temporarily trapped in there (though it will eventually find its way out over time).

By the way, I just want to throw this out there for any potential naysayers:
This spring I replaced my master with a new 3g unit and ALL the hard lines (yes ALL including the rear lines) with ss braided AND I PURPOSEDLY DID NOT BENCH BLEED the master (because it's too big a PITA). I bleed all the calipers once at the start and once again about a week later just for peace of mind. The results: about four months and 10,000 kms later, no air in the system, no leaks, nothing but a firm pedal from day one.

Anyway, what's my point? The point is, even if your m/c wasn't bench bled 100% correctly and you still have some air in there, it will eventually find it's way out (either through the reservoir or out to a caliper). But the fact that you keep getting "new" air after every bleed points a finger at the master introducing some over and over.
 
Ok I will try that.

The thing that concerns me is that I bleed the system untill I get no more air bubbles coming out. Then I press the brakes to see what kind of pressure I have, which hasn't been good. And then go around to bleed again I get more air coming out.

I just can't see where the air is coming from. There are no leaks at all.


Air must be getting sucked in from the bleeders and or the master cylinder.


-Gary
 
I am going to try some Teflon around the bleeders. If that's not it I will probably just swallow the bullet and buy the OEM Mitsubishi part and call it a day.

I will report back with what I come up with.

Thanks for the responses.
 
Ok so I tried a few things. I got some longer speed bleeders and put some thread sealer on them. I was able to get the system fully bled.

After that my brakes wouldn't fully engage until the pedal was about half way down. I adjusted the linkage as much as I could but came to no success. I ended up buying the 3G 8+9 brake booster. I installed that. Adjusted the linkage and BAM problem solved!

Car is back up and running again. Thanks everyone for the help.
 
Solution
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