Topic: Contaminated Brake Lines

[kkupec02]

What would cause contamination in the brake lines to erode the seals of the master cylinder and wheel cylinders in 5 months? I just had the master, booster and distribution block rebuilt. The car then had the engine rebuilt over the past 5 months for a no vacuum cam shaft. During that time, the new master seals broke down and leaked into the new booster. The wheel cylinders began to weep. I wish I had drained the system. What could have contaminated the system? Fortunately, it doesn't look like the new rebuilt caliper pistons are leaking

[Bob Gaines]

What would cause contamination in the brake lines to erode the seals of the master cylinder and wheel cylinders in 5 months? I just had the master, booster and distribution block rebuilt. The car then had the engine rebuilt over the past 5 months for a no vacuum cam shaft. During that time, the new master seals broke down and leaked into the new booster. The wheel cylinders began to weep. I wish I had drained the system. What could have contaminated the system? Fortunately, it doesn't look like the new rebuilt caliper pistons are leaking

It may have to do with the brake fluid acting on the seals. For example I have had some rebuilders tell me that the Dot 5 silicone is not compatible with some seals and will leak. They will not warranty them for that reason . Dot 3 is the typical Dot 4 is supposed to be higher temperature. I would think that the seals would be made for Dot 3 and 4 .Just some thoughts. 

[Murf]

Like Bob, I would suspect DOT 5 brake fluid is the culprit.  Most rebuilders of brakes caution against using silicone brake fluid and will not honor a warranty if it is used.  Tons of reading on this subject if you care to investigate.  I have been the victim of a master cylinder seal leaking into a Midland-Ross booster and causing a troublesome (as in expensive) repair.  Hard lesson to learn!  Please give some details of parts and fluid used in your repair.  Normally, the smaller the diameter of the seal the sooner it will fail.

[67gtasanjose]

For what it is worth, regarding previous comments on using DOT 5 (silicone) fluid:
I rebuilt all my brake cylinders myself and used DOT 5 as my assembly lube. I also rebuilt my distribution block and my disc brake residual valve, using DOT 5 as the assembly lube.
Zero issues after 1 year.

[Bob Gaines]

For what it is worth, regarding previous comments on using DOT 5 (silicone) fluid:
I rebuilt all my brake cylinders myself and used DOT 5 as my assembly lube. I also rebuilt my distribution block and my disc brake residual valve, using DOT 5 as the assembly lube.
Zero issues after 1 year.

I have used DOT 5 before too with no problems. I can only assume that there is something to the compatibility with some seals however given the apprehension of many rebuilders that you send Masters, wheel cylinder , proportioning valves and calipers to. I am not condemning the silicone just trying to make sense of the OP?s problem.

[kkupec02]

I got the car from California with a shot master which bled into the booster and wrecked that as well. The prior owner said that he refilled the master several times as it was getting ready for transport. Filled with what? Whatever was on hand like Dot 5? I got the car and spent $600 to get the master, booster and distribution block rebuilt by Karp's Power Brake Service. I installed the parts with a new container of Prestone Dot 3 only to find that I still had no brakes. I found that the cam in the engine was producing no vacuum. That cam was put in by the prior owner then the car was put back in storage. I don't have the skills to take an engine apart. So, I bring it to Cobra Automotive. Down the rabbit hole I went. $10k later, I have vacuum with a totally rebuilt engine, rebuilt carbs and a new correct exhaust system. But, while the car was there for 4 months, my Dot 3 must have interacted with whatever the prior owner had in the system. My mistake was in flushing the radiator, changing the oil, but not flushing the brake system when I worked on it. So, I now lost all of my rubber parts in the system. The only issue left that Cobra Automotive is fixing today is a chatter in one of the front disk brake pads while braking. Total now probably $11k with replaced master, booster parts. Wanted to understand so I at least get a lesson for the future.   

[Bob Gaines]

Dot 5 and Dot 3 or 4 do not mix. The fluid has a tendency to gel up when in contact with each other. Yes if in question flush the system how ever if suspected Dot 5 you would need to flush with alcohol first to get rid of the dot 5 and add Dot 3 /4 . Same if going the other way . Also calipers ,wheel cylinder, master and proportioning valve should be re assembled using the brake fluid to be used to get rid of any trace. I have done it successfully without disassembling the mention items but that is not the best way.

[Dan Case]

For what it worth I tried two brands of DOT 5 in two cars (1965 GT350 and a Cobra) twice each in the 1980s.  Between the two cars six (6) total overhauls of hydraulics got me back to standard type fluids.  With DOT 5 fluids something was leaking past a rubber seal somewhere or another all the time. That included starting of with new old stock Ford cylinders and proportioning valve in the GT350. I also had issues with locking the brakes up when brake master cylinder pistons would not retract. The Cobra had an issue with the clutch slave cylinder piston not retracting.

In 2003 we bought a car that somebody put silicon based fluid in. One wheel's brake barely worked. The other three were locked up. Silicon fluid from leaks contaminated part of the engine bay and all the underside of the car, front suspension, and rear suspension. Every "rubber" seal had hardened and some literally had tiny cracks in them.  Another issue was there was a small amount of liquid water in everything. (Anywhere brake fluid can get out, water can get in.) Everywhere water was there was red rust. The backs of caliper pistons were so rusty I didn't think I was going to be able to get them out (rust had locked up three calipers). I had never seen that much corrosion in a hydraulic system before.

It is my understanding that chemical resistance all depends of what the "rubber" was exactly. Girling(R) rubber compounds from the 1960s-1990s started off as tree sap and reacts poorly with silicon based fluids.

Girling started including this warning leaflet with new hydraulic components after user issues surfaced.




Yes, some people have had great success with their cars and "silicone" fluids. The problem is that not all "rubbers" people might buy are the same and not all the fluids are chemically the same to the last additive.  Just buying parts and fluids may or may not come up with a compatible 'system'. I tried two cars twice each and that was a lot of work just to have the same failures repeat.

[kkupec02]

Thanks. My seals swelled and leaked after 17 weeks of putting in new parts.

[67gtasanjose]

...fluid can get out, water can get in.) Everywhere water was there was red rust. The backs of caliper pistons were so rusty I didn't think I was going to be able to get them out (rust had locked up three calipers). I had never seen that much corrosion in a hydraulic system before..

...Yes, some people have had great success with their cars and "silicone" fluids. The problem is that not all "rubbers" people might buy are the same and not all the fluids are chemically the same to the last additive.  Just buying parts and fluids may or may not come up with a compatible 'system'. I tried two cars twice each and that was a lot of work just to have the same failures repeat.

I attribute the success that I experienced (DOT 5) with the use of all newly-manufactured rubber products (excepting the brake hoses). Master Cylinder kit bought through my Napa store and wheel cylinder/caliper kits are Raybestos products.
The distribution block seals and the residual valve kits both came through WCCC's site. I imagine the old EIS branded Single-Crimp hoses I used are of the "old rubber" line of products...I will keep an eye on them.

I do occasionally drive my car. The brake pedal is fine (not spongy). The best advantage of using this fluid is that the fluid helps to PREVENT corrosion from water absorbing into the fluid. Time will tell.
A few years ago (when building these components), the use of DOT 5 was said to be a better product for a rarely driven car.

There was a thread on it at this site:
https://www.concoursmustang.com/forum/index.php?topic=17855.msg112808#msg112808

[Dan Case]

To keep a dried hydraulic brake system completely free of water means nothing can leak. I have opened up systems with ?silicone fluid? that had considerable liquid water inside and rust corrosion just because of defective cap seals or caps that did not fit correctly.  Hot air expands to leak out of reservoir head spaces and then during cool down cool damp air is drawn in.  Just having DOT 5 fluid alone does not equal a dry system in every car automatically, just too many variables. I have helped quite a few old Ford owners finding water then their silicone fluid filled systems because reservoir and or cap seal issues.  When you drain these water contaminated systems into a clear container the water droplets are easy to see. Rust, not every brand of DOT 5 fluid seems to have the same corrosion inhibitors and or levels of them.  (Yes, in Cobras aluminum hydraulic cylinders can suffer corrosion also.)

Any situation that allows "wet" air into the head space of a reservoir sets up a situation for water to condense out as liquid droplets on all upper head space surfaces if the temperature is reduced enough. I would not expect droplets, they can be quite tiny, to "absorb" into a silicon based fluid. They can migrate down under vibration and gravity to the fluid below them. Lots of microscopic droplets can gather and form larger droplets.

[69supercj]

I ran DOT 5 Rabestos silicone fluid in my car for 12 years with zero issues. Then the car sat for 15 years. I just recently tore the master cylinder apart and it still looked like new and the seals were pristine. I'm gonna put the DOT 5 back in it.