Water in slave cylinder.

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Author Topic: Water in slave cylinder.  (Read 1435 times)

Offline coops

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Water in slave cylinder.
« on: April 05, 2021, 09:37:19 am »
This morning I attempted to fit new brake linings to my 69 Mustang. When I stripped it down I noticed rusty water dripping from the slave cylinder. It has damaged the slave cylinder beyond repair. It is on the outside of the piston and the piston still pushes in and out. Where would this water have come from? I have notice for some time that when the car sits for a while and you attempt time move it the rear brake are locked on but free up as soon as you give it a bit of gas. Any advice is greatly appreciated. Cheers Coops and Happy Easter
66 and 69 coupes.

Offline AussiePhil

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Re: Water in slave cylinder.
« Reply #1 on: April 05, 2021, 12:37:59 pm »
Hey coops,
I've always believed that parking on wet or damp grass draws water from the grass and the humidity enters hot items, exhaust and possibly slave cylinders, rusting them prematurely. My uncles told me that 50 years ago!
I'm sure someone will post back it's total bullshit! But I've got big shoulders, and it wouldn't be the first time!
Cheers Phil.
If you've never buggered anything you've never done anything!
But if you've buggered a lot maybe you're not very good at it!

Offline Reborn67

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Re: Water in slave cylinder.
« Reply #2 on: April 05, 2021, 03:58:58 pm »
 Sorry Phil, I'm not calling bullsh!t on that one 'cause I've never heard that one before and nothing would surprise me, but I do know that brake fluid is very "hygroscopic" meaning it will absorb moisture easily. You would think that a sealed Brake line system would prevent this but it Does get in, via seals and the porosity of brake components, I believe some fluids are less prone than others, but failing that it may just come down to bleeding the system out more often, which is not a bad thing anyway...,

Offline AussiePhil

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Re: Water in slave cylinder.
« Reply #3 on: April 05, 2021, 07:18:05 pm »
Hey coops,
Totally agree with reborn67, when was the last time they were flushed and fluid replaced!
Old saying, oils cheap, and it's not a hard job if they're already bleed. Get a good fitting ring spanner!
A lot of people say the repo slave cylinders are rubbish but I haven't found that.
I had a funny thing the other day, I changed my parking brake shoes and realised my calipers were on the wrong sides, with the bleed screws on the bottom, I fitted them that way when I fitted my four link suspension! I must have bleed them off the axles! Anyhow I've put them on the correct sides!
Cheers Phil.
« Last Edit: April 06, 2021, 01:08:43 pm by AussiePhil »
If you've never buggered anything you've never done anything!
But if you've buggered a lot maybe you're not very good at it!

Offline AussiePhil

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Re: Water in slave cylinder.
« Reply #4 on: April 05, 2021, 07:24:05 pm »
This morning I attempted to fit new brake linings to my 69 Mustang. When I stripped it down I noticed rusty water dripping from the slave cylinder. It has damaged the slave cylinder beyond repair. It is on the outside of the piston and the piston still pushes in and out. Where would this water have come from? I have notice for some time that when the car sits for a while and you attempt time move it the rear brake are locked on but free up as soon as you give it a bit of gas. Any advice is greatly appreciated. Cheers Coops and Happy Easter
Hey coops,
As for the shoes grabbing check your shoe return springs are ok!
Cheers Phil.
If you've never buggered anything you've never done anything!
But if you've buggered a lot maybe you're not very good at it!

Offline coops

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Re: Water in slave cylinder.
« Reply #5 on: April 05, 2021, 07:54:58 pm »
Thanks Guys. I have had this Mustang for about ten years and have never thought to flush out the brake fluid when the brakes were working fine. I'm trying to identify the front brake caliper and when I do I'll be ordering new slave cylinders from Griffs and if the caliper are Mustang I'll get a set of pads as well sent up to me. Thanks for all the great advice. Cheers Coops
66 and 69 coupes.

Offline pmb0186

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Re: Water in slave cylinder.
« Reply #6 on: July 30, 2021, 03:53:22 pm »
I had the same problem and as a result rebuilt everything.
Found wheel cylinders and master cylinder corroded(replaced) luckily the front callipers were fine but had to disassemble so put a seal kit through them.
I now own a brake fluid tester and replace fluid regularly 
does anyone remember laughter

Offline minipete

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Re: Water in slave cylinder.
« Reply #7 on: July 31, 2021, 09:07:06 pm »
Water in the brake fluid comes from water vapour in the air that is ingested via the breather hole on the master cylinder. 

Modern MC's have a rubber membrane that allows the fluid to drop with brake shoe/pad wear without air getting in but it still does every time you open the master cylinder to check it.

It's only a small amount of water so if you change the fluid every 2 years it never becomes a problem.

Offline pgold

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Re: Water in slave cylinder.
« Reply #8 on: August 01, 2021, 08:53:39 pm »
Coops, If you take disk pads from one side to your local REPCO they have a catalogue with actual size drawings of disk pads they sell. If there is no part number on yours just overlay your pads to matching drawing. I did this a couple years ago for brake pads for a boat trailer with unknown brakes.
Also check your drums are within wear limits. From memory 10" + 60 th. Mine had been machined oversize and weren't working correctly. Replace springs while your at it - kit with pins, clips and springs is about $25.

Offline 66FBK

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Re: Water in slave cylinder.
« Reply #9 on: August 04, 2021, 10:36:26 pm »
Phil I have had the same thing with corrosion inside the master cylinder causing sluggish brake feel. The brake fluid was rusting brown. All brake components (master cylinder, lines, calipers, slaves) were replaced 7 yrs ago. That's what you can expect if your car is not a daily driver. Brake fluid absorbs moister and your master cylinder breathes outside air every time you but your foot one the brake. I had to rebuild the master cylinder and flush the whole system and it is now good for now. I will now flush the fluid every year or so. I am not sure if synthetic brake fluid is any better but brake fluid is a strange  science.
He, with the most toys wins.

Offline AussiePhil

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Re: Water in slave cylinder.
« Reply #10 on: August 05, 2021, 06:35:11 am »
Hey all,
Been a few years now since I fitted my brakes.
I’ll put on my to do list to replace all the brake fluid.
It’s not as if we have anywhere to drive at the moment! :sick:
Oils cheap, it’s just a horrible product to use and cleanup!
All the chemicals used to make it anti boil, not good for your health and takes the paint off.
Thanks for the reminder!
Cheers Phil.
If you've never buggered anything you've never done anything!
But if you've buggered a lot maybe you're not very good at it!