why is my brand new master cylinder seeping?

[txchainsawgogi]

its clean on the inside, fluid looks good. for some reason its flash rusting in some spots and it looks like its leaking from the top AND around where it connects to the booster. why is it doing this? am i gonna just not have brakes one day?

[Irish_Alley]

make sure the gasket is on the cap right

[beastie_3]

cant that reservoir be swapped out for a newer model? The aluminum and plastic one?

[txchainsawgogi]

I don't know if it can be swapped. Id like to since this new one will just be covered in rust in a few months...it hasn't rained in texas much what with the 105+ degree heat.

[beastie_3]

i have the same one and it rusted quickly too.

[VileZambonie]

Brand new or remanufactured? Either way replace it. If you don't like the look of rust paint the new one before you install it and make sure after you install it that there is no brake fluid residue on it.

[txchainsawgogi]

that one was new! And I rustoleum'd it haha. I don't get it... I guess my only option is a plastic one.

[paniolo]

If it is leaking around where the base mounts to the power booster it has bad seals and needs replaced.

The top was probably just spilled when you were taking it off, but double check the rubber seal on the top to make sure it isn't ripped anywhere.

[txchainsawgogi]

The seals were good though... I cleaned the heck out of the mounting area too. Could it have anything to do with the booster? That thing is original.

[TxFiddler]

I had same problem.  I found that the bar that holds the top down was not putting enough pressure down to seal the cap.  Pop the top off and remove the hold down bar.  Bend the angle of the bar so that it will fit tighter.  The angle of the cylinder is causing it to leak out of the rear of the rubber gasket.  Mine has not leaked since and it was also brand new and messed up my paint job as well.
Fidd

[paniolo]

The seals were good though... I cleaned the heck out of the mounting area too. Could it have anything to do with the booster? That thing is original.

No it can't be the booster cause that has no break fluid in it ... just a vacuum.  Fluid in that area could be leaking down from above if the rubber is ripped or the bail is not tight enough.  Or else it is coming from the bore and getting around the seals when pressure is applied.  How did the bench bleeding go? 

[VileZambonie]

Brand new or remanufactured? Either way replace it.

Don't waste too much brain power on it. Just replace it.

[txchainsawgogi]

Bench bleeding was fine... can anyone tell me if they make a plastic version for our trucks?

Seems like the plastic ones would be for modern applications only.

[VileZambonie]

A quick take up master cylinder uses the plastic reservoir and yes you can get them for our trucks.

[1980c10]

I replaced mine with a booster and master cylinder from an '85 k10
The '85 master would not bolt up to the old booster, but the '85 booster bolts up to the truck. So I swapped both.