Help - Brake Problem

[Bigblue73]

I finally got my wifes Cuda running the other night, I took it out on the road and noticed nothing, everything was fine. I popped the hood and found brake fluid dripping from the master cylinder cover. I pulled another master cylinder cover off of my Challenger and same thing. The master cylinder never did this before. Problem? Any Ideas?

The brakes are the stock power disc brakes that have been gone thru prior to all this swapping. Any ideas? I'm sick cause it trashed the paint on the inner fender. The car has headers - but the header are pretty far away from the master cylinder, at least 8 - 10 inches.

Thanks, for any advise.

[MrQuick]

are you running line lock?

[Railing68]

When I did my last swap (a couple of months ago) I used a rebuilt mc the first time and it leaked from the cap badly. When I bled the brakes the gasket didn't suck down as the fluid was expended!

Since the bad mc wouldn't do this it appears to an indication of the problem. I ended up replacing the MC, Sorry I don't have a quick fix. SS

[Bigblue73]

No line lock....Thanks for the help. It just seems odd that it would leak from the cap though.

[LTorres]

You never know.

Is the MC located in the OE position firewall/booster?

[Bigblue73]

Lamarie - Stock OE position with booster. What are your thoughts?

[LTorres]

Lamarie - Stock OE position with booster. What are your thoughts?

Both cars......same problem? hmmmm......I would be checking into system contamination. As embarrasing as it may seem to the offender, who, when, and what was installed for fluid (perhaps it was topped off within the last few months).

As you may know system contamination of the worst kind happens when any petroleum based product is introduced into the system. When this happens every rubber component in the system swells or bloats and will do all of the following.

1. Since the system is a closed circuit hydraulic system any swelling of rubber will cause brake drag at the wheels.
2. In a brake system rubber components upstream of the combination valve, prop valve or metering valve will cause pressure at the MC. The easiest route for this pressure to escape is right out of the MC lid.
3. Since the seal used in the MC is also rubber a swollen part will not allow a perfect seal, thus escalating the problem and allowing the fluid to be visible outside the MC.
4. There is more but I'll stop here.

How do you find out without buying any expensive test equipment?

Try this:
1. Remove the MC cap and check rubber for any abnormalities or swelling. If your not sure that swelling is present have a qualified brake tech check it for you. Most will do this FREE since they merely open the hood and check it.

2. If there is enough swelling to cause fluid to esacape out of the seal, then you most likely have contamination as far down as the rubber hoses and or calipers. Jack the vehicle up, depress the pedal like you would in a panic type stop, release all pressure from the pedal, step down and rotate each wheel. All 4 wheel should rotate freely with no bind.

It is just too uncanny that 2 vehicles suddenly have the same problem. Doesn't it make since that since both MC lids are leaking at approximately the same time that abnormalities in the MC seal are highly unlikely to have occured without the introduction of a petroleum based product?

Easy mistake to make.....if this is the problem feel free to ask and I can explain how you go about resolving it. Good luck.

If this is not the issue then I am stumped without inspecting each vehice myself.

Hope this helps

[fuzzyonion]

Also 2 things which will make a poor cap seal seem worse:
Make sure you dont overfill. If you have a service manual for the vehicle, check the filling instructions. It can often be a good 1/2" from the top as the spec.

If there is any air in the system, there will be a significant fluid geyser inside the master when you release the brakes.

An easy way to check for oil contamination in the brake fluid is to take a teaspoon of the fluid and drop it in a jar of water. It should turn cloudy. If it separates, it is most likely oil contaminated which will swell the seals (or it has DOT 5 fluid in it). DOT 3,4 and 5.1 will turn the water cloudy.

[Bigblue73]

My Challenger is fine. I just swapped the master cylinder cover from my car to hers.
My wifes 'cuda is the problem child here. I'm pulling the master cylinder tomorrow night after work.
As far as contamination....I'll try that thanks.

[LTorres]

Also 2 things which will make a poor cap seal seem worse:
Make sure you dont overfill. If you have a service manual for the vehicle, check the filling instructions. It can often be a good 1/2" from the top as the spec.

If there is any air in the system, there will be a significant fluid geyser inside the master when you release the brakes.

An easy way to check for oil contamination in the brake fluid is to take a teaspoon of the fluid and drop it in a jar of water. It should turn cloudy. If it separates, it is most likely oil contaminated which will swell the seals (or it has DOT 5 fluid in it). DOT 3,4 and 5.1 will turn the water cloudy.

Good call Fuzzy Onion......when I used to check for contamination via water test I would use styro-foam cup. It seemed as though contaminated fluid would not only show the oil floating in the water, but it would eat through the cup, very quickly.