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Old 02-22-2021, 01:38 PM   #1
NeoJuice
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Where's the brake fluid coming from?

Just finished bleeding all the lines a couple weeks ago and finally have no leaks. I've been testing for leaks every couple days giving the pedal about 10-20 pumps then checking all my lines/connections after that.

Checked the underfloor booster yesterday and found two drops under the master. I checked it a couple weeks ago and had the same drops in the same place. Just as I did a couple weeks ago I cleaned everything up and made sure everything was dry and lid on tight & I'm wondering why this is happening and where the fluid is coming from.

Since its an under floor booster there is nothing above it that could be leaking down onto the master. If fluid was coming from the little weep hole it would be on the master next to the booster and not on the other protrusion.

Could the fluid be slowly seeping down and collecting on those two posts from the lid? Could I have the two fluid bowls to full and as the system relaxes cause a leak? The fluid looks a little darker I believe because there is a small amount of rust on the master even though it's brand new.

Any thoughts would be appreciated. Thank you.
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Old 02-22-2021, 02:04 PM   #2
mr48chev
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Re: Where's the brake fluid coming from?

It's real easy to over fill an under floor master cylinder.

I've never heard or read anything on any master cylinder having a weep hole.
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Old 02-22-2021, 05:12 PM   #3
Wrenchbender Ret
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Re: Where's the brake fluid coming from?

Sounds like the MC is leaking at the piston seal. Can you unbolt the MC & pull the MC back a ways to see if fluid is in there?
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Old 02-22-2021, 06:47 PM   #4
NeoJuice
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Re: Where's the brake fluid coming from?

I didn't know if that was a weep hole or not lol.

I can pull off the master cylinder to check if the fluid is coming out of the rear of the piston shaft. If that was the case, fluid should be dripping down the booster onto the ground and onto the bottom/back part of the master. (if that makes sense)

The thing that doesn't make sense is how the fluid got onto the second 'nubby' I'll call it. So I would suspect that the fluid must be weeping down from the lid.

I'll have to pull the cover off the floor and the lid off to see how full the bowls are. If they are to full that might be the problem?

Any thoughts appreciated.
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Old 02-22-2021, 07:25 PM   #5
geezer#99
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Re: Where's the brake fluid coming from?

Splash some baby powder on the master and booster and any leak tracks will show up.
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Old 02-22-2021, 10:59 PM   #6
dsraven
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Re: Where's the brake fluid coming from?

I would loosen the master from the booster and check for dampness in that cavity. grab some brake clean and dry the area up. then tighten it back up and pump the pedal a few times like you were. then go back under and loosen/recheck. if it is dry then do the baby powder trick and leave it for a few days, pumping the brakes like you have been doing. if it is a lid seal leak that will show up easily. sometimes the lid seals on rebuilt units aren't that awesome and the little fountain of fluid that happens when when the brakes are released can sometimes cause enough disruption in the reservoir so the fluid makes it's way out the lid seal. the lid should also be vented so you could check that too.
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Old 02-23-2021, 11:35 AM   #7
NeoJuice
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Re: Where's the brake fluid coming from?

Thanks for the suggestions and I'll give them a try. I'll report back when I have a chance to follow the suggestions.
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