Master Cylinder leak?!

[suki243]

I think i have a master cylinder leak; A few months ago the level was completely fine, filled up to the brim. Then the other day while trouble shooting my power steering (another thread) i happened to check the brake fluid level , and my god it was almost dry and all the way to the bottom the outside of hte cylinder is partially. wet, and if i look down i can see the paint corroding off the apron.

I looked at the grommet rubber thing underneath and it was kinda messed up so i fixed it and put it back in, now i'm wondering if it was in the right way or not. is the flat surface supposed to be pointing town to the bottom of the car after screwed in; or should it be up? I put it pointing down, and drove back to school, and when i popped the hood just to check the master cylinder was covered with brake fluid, soaking wet (pic below), and the level had decreased. I drove around and added some fluid, and now i put it the other way, with the flat surface pointing up to the sky after it's screwed in.

The cap is on tight btw.

View attachment 259557

 

[Steve S]

Hi,

I saw your other thread and i think i could see some fluid on the under side also, i don't know about the single bowl set up but the dual bowl is not supposed to be full but only about 3/4 from the top. I guess the rubber gromet you are talking about is the thing under the lid, once again if it is the same as the dual then it should be pointing upwards.

Get the fluid cleaned up and identify exactly where the fluid is coming from. It might not be the master, check the inside of the wheels from under the car, if you can see fluid on the backing plates then you probably have a slave leaking.

Steve

 

[suki243]

I only filled it 3/4ths this time cause when i switched the grommet around to the flat level up it made the cylinder overflow. so i scooped some out and closed it again. But i just went to get dinner came back and checked and it overflowed again. I checked the manual and it has the flat side down. Yah I'm talking about the thing under the lid

(if anyone's confused what i mean the flat side up or down, in the figure below it is what i've been referring to as the flat side down.)
Perhaps its a bad cap
View attachment 259554

This is a pic of the cap after i got dinner.
View attachment 259555

TIA for all your help.

 

[2+2GT]

Clean it very carefully, so that there is no trace of fluid, and check to see where it becomes wet. That's a LOT of leak, so it should be easy to spot. It will either be a connecting line, or the rear of the cylinder. The cap seal cannot do this.

 

[2nd Mustang]

Does the car brake okay? Sometimes if the MC is leaking internally or a brake line is blocked, instead of the fluid going to the brakes, it will bubble up like a geyser back into the reservoir.

 

[suki243]

Hmm, I felt that when the fluid was low the brake pedal was spongier, but as soon as i refilled it it became stiff as i used to remember it. Besides that Braking is normal. The spongier braking is actually what made me drive around for 20 minutes trying to find somewhere that sells brake fluid that late, I hear that air bubbles get into the system = catastrophe.

I'll try this week to clean it up really well and put the car up to see how it is underneath. It's definitely leaking somewhere cause if you look carefully at the bottom you can see the fender apron's paint coming off, and steering column is usually wet in places.

It might be that hard line in the front, cause a few times the outside of the cap itself was wet, could it be a very very small leak there that is causing fluid to shoot backwards? as well as a bad cap? cause i'm not sure how else it could spew out like that, when you open the cap the groves are soaked as well.

 

[suki243]

Hey guys, a little update; I took it to a few mechanics and most agreed that it was just the cap. So i went to NPD bought a scott drake repro cap, it's metal. I put it on and no luck it's actually worse it spews out, my dad drove the car for a week and i came home hte other day and turned the car on to circulate the fluids and noticed that the brake pedal goes to the floor! I immediately check the resevior and its almost bone dry. I quickly fill it up, go for a test drive and its leaking enough to drip to the floor, it runs down to the frame rail and drops down slowly. I changed the cap to the original plastic one and went for another test drive and practically none came out. Idk what to do... any suggestions?

Edit: I crawled underneath and i checked the cable behind the wheel, and it seems fine, but i followed the trail of fluid and my god the whole thing is wet, the steering shaft, the side of the engine bay wall that comes down, the side of the power steering ram, the frame rail ont he bototm, and the entire underside of the master cylinder and brake booster.

My reasoning for thinking the cap is the culprit, it looks as if its coming from underneath, when you unscrew it the threads are soaked.

Also it potentially has bubbles in the lines, should i take any precautions?

 

[suki243]

Sorry for no 56k warning

With the new cap

Without a cap on

This is where its dripping to the floor

Following the trail

Looking up to the power and master cylinder.

 

[2nd Mustang]

Being such an older classic car, I wouldn't fiddle too much with small things here and small things there.

I did that with my braking system and regretted it. I eventually just bit the bullet and replaced all components, even some of the corroded hard lines. I'm on my second MC/brake booster combo, second new calipers and rotors in the front. new shoes and drums in the rear along with new spring kit and cylinders. New distribution block, etc.

I do like to drive hard but stopping is also important.

Good luck.

 

[Grabber70Mach]

I'd get rid of the single bowl M/S (jellyjar) and go with a safer dual bowl setup.

 

[suki243]

Has anyone done a single to dual bowl switch? How much $$ and time does it take?

As for an update, my grandpa was over the other day and i told him teh problem, we popped the hood looked at the two caps and noticed the new one's gasket is flimsy as heck, we then looked at the bowl itself and he noticed that top had some rust on it, we sanded down the rust spots down a bit, cleaned it back up, closed it up, went for a test drive and gosh darn it no leak so far, i'll keep an eye on it and let you guys know how it holds together in a few weeks

 

[Grabber70Mach]

Here's a link to one kit.

http://www.parts123.com/parts123/yb.dll?Parta~PartSort~A0~~~~~A30~A21

I'm not 100% sure, but I think you can use a manual MC setup from a 70's Maverick. I'm sure someone with more knowledge will chime in about that.