Fluid resivior leak?

[Suburban]

Last night coming down the mountain my brake light came on on the dash and the pedal went to the floor. I could still stop the truck. Looked under the hood and fluid was leaking all aroun the resivior cap. Could it just be the cap leaking? Or the cap gasket?......I went on down the mountain with the pedal on the floor once I stopped in the road ....the light went off and the brakes suddenly felt good.....stayed feeling good the rest of the way home......trying to decide what to fix today....................


Take it easy on the new guy

 

[89Suburban]

Is the level in the reservoir dropped at all from the last time you checked? Did you look around behind all four wheels for any wetness? If they are all dry I would suspect the master cylinder is going out. Usually it will be wet around where it mounts to the brake booster when that happens.

 

[chengny]

For brake fluid to escape from the master cylinder - with the cap on - that's not something you see every day.

Usually only happens while installing new brake pads (when you forget to lower the level before compressing the caliper pistons).

But it can happen under severe braking conditions especially if the fluid is old and has a high water concentration.

How big was this mountain you were coming down? Were you continuously braking for a long time? Did you have a heavy load in the bed (pulling a trailer)?

The only thing I can think of is that your brake fluid is contaminated - it has accumulated an excess amount of water.

Brake fluid is hygroscopic (tends to absorb moisture) by design - to prevent pockets of liquid water which can freeze/boil. But it can only absorb so much; eventually it becomes saturated, and water pockets form in the brake lines and other components.

Due to the heavy braking as you descended the mountain, it became overheated and the water boiled out. Consequently, it's volume expanded and it's viscosity became extremely low. This would explain the temporary loss of pedal. When things cooled down, the viscosty returned to normal and the master was again able to pump normally.


Also due to the steam in the system, the volume was increased. This increased volume caused the fluid to rise and the associated pressure increase made it squeeze out of the gasket.


That's just a theory, but I would do a thorough flush of the brake system.

 

[Suburban]

Thanks for the help.....

I think I will start with the fluid flush it being the cheapest.....then on to the master cylinder....I tried to post some pics with no success.....not wet behind the wheels ....and was continually breaking down the mountain....

 

[Suburban]

Fluid looks terrible

And the fluid looks terrible...............

 

[smurph20]

What i am reading it that it was wet around the cap not the back correct? Then yes sounds like the cap either wasnt on all the way or has a bad spot on it. At an angle coming down the moutain maybe it was enough for it to flow out of it.

 

[philjafo]

And the fluid looks terrible...............

This would be reason enough to replace the fluid, and also what chengy said.

 

[Suburban]

Thanks for the help

New master cylinder....I took the old one loose.....there was a small amount of fluid on the booster..so new master cylinder front brake pads and fluid...truck drove good coming down last night....

 

[89Suburban]

You must be registered for see images attach

 

[TexasOutlaw87Cummins]

Mine does the same thing ... Did it fix your problem ?

 

[Suburban]

Yhea fixed

Yhea it fixed it........but I just can't shake the feeling of not finishing the job with doing the rear brakes too.......