73-87chevytrucks.com

73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: txchainsawgogi on August 21, 2011, 10:11:02 pm

Title: why is my brand new master cylinder seeping?
Post by: txchainsawgogi on August 21, 2011, 10:11:02 pm
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?

Title: Re: why is my brand new master cylinder seeping?
Post by: Irish_Alley on August 21, 2011, 11:53:01 pm
make sure the gasket is on the cap right
Title: Re: why is my brand new master cylinder seeping?
Post by: beastie_3 on August 22, 2011, 10:18:19 am
cant that reservoir be swapped out for a newer model? The aluminum and plastic one?
Title: Re: why is my brand new master cylinder seeping?
Post by: txchainsawgogi on August 22, 2011, 11:27:09 am
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.
Title: Re: why is my brand new master cylinder seeping?
Post by: beastie_3 on August 22, 2011, 11:34:09 am
i have the same one and it rusted quickly too.
Title: Re: why is my brand new master cylinder seeping?
Post by: VileZambonie on August 22, 2011, 11:41:03 am
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.
Title: Re: why is my brand new master cylinder seeping?
Post by: txchainsawgogi on August 22, 2011, 12:50:59 pm
that one was new! And I rustoleum'd it haha. I don't get it... I guess my only option is a plastic one.
Title: Re: why is my brand new master cylinder seeping?
Post by: paniolo on August 22, 2011, 01:29:59 pm
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.
Title: Re: why is my brand new master cylinder seeping?
Post by: txchainsawgogi on August 22, 2011, 03:52:57 pm
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.
Title: Re: why is my brand new master cylinder seeping?
Post by: TxFiddler on August 22, 2011, 03:53:41 pm
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
Title: Re: why is my brand new master cylinder seeping?
Post by: paniolo on August 22, 2011, 07:43:01 pm
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? 
Title: Re: why is my brand new master cylinder seeping?
Post by: VileZambonie on August 22, 2011, 07:47:49 pm
Brand new or remanufactured? Either way replace it.

Don't waste too much brain power on it. Just replace it.
Title: Re: why is my brand new master cylinder seeping?
Post by: txchainsawgogi on August 22, 2011, 08:37:02 pm
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.
Title: Re: why is my brand new master cylinder seeping?
Post by: VileZambonie on August 23, 2011, 08:19:45 pm
A quick take up master cylinder uses the plastic reservoir and yes you can get them for our trucks.
Title: Re: why is my brand new master cylinder seeping?
Post by: 1980c10 on August 23, 2011, 10:51:16 pm
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.
(http://i686.photobucket.com/albums/vv222/titera1/DSCN0591.jpg)
Title: Re: why is my brand new master cylinder seeping?
Post by: 1980c10 on August 23, 2011, 10:55:33 pm
btw; if the master cylinder leaks out of the back it needs to be replaced, if you dont the brake fluid will get in to the booster and ruin the diaphragm and you'll need to replace that as well.
Title: Re: why is my brand new master cylinder seeping?
Post by: beastie_3 on August 25, 2011, 12:25:23 pm
So to upgrade, you need both the booster and master cylinder for a 85? Is there any braking benefit from upgrading, or is it just looks/style?
Title: Re: why is my brand new master cylinder seeping?
Post by: 1980c10 on August 25, 2011, 12:52:27 pm
The newer booster is physically bigger and the top doesn't leak on the master. My brakes felt fine with the older style as well. So I don't really know if the newer style better or the same but the fact that it doesn't leak and looks better was enough for me.
-The 85 master would not bolt up to the 80 booster. I had the 85 booster so I installed that as well.
This is an easy salvage yard find as long as there are no signs of leakage.
I consider it a nice little improvement for little money and little effort. It was a good time for me to re-do my brakelines as well.
Title: Re: why is my brand new master cylinder seeping?
Post by: txchainsawgogi on August 27, 2011, 04:03:26 pm
so is there a direct fit plastic reservoir replacement for a 1978 2WD 350 c10 silverado? i cant seem to find one. will another year bolt up ok or am i stuck having to go find a booster from an 80's blazer?
Title: Re: why is my brand new master cylinder seeping?
Post by: 1980c10 on August 28, 2011, 05:36:01 pm
I think it would be easier to just find a newer booster than trying to find something aftermarket and if you needed to replace it in the future it would also be nice to pick one up locally. These are not hard to find and you can buy them new if you choose. I think the boosters are about 99 and the master cylinders are about 40.