When was the last time you changed the brake fluid?

Most (DOT3) brake fluid is highly hydroscopic (IE it absorbs water easily) and just 3 % water in your fluid will drop the boiling point of the fluid by 100F...creating bubbles and loss of braking power.

Try having the fluid replaced with DOT 4 synthetic (Not Silicone, I repeat NOT SILICONE) which doesn't have the affinity for water like the DOT 3 does.

 

I've never changed the brake fluid. If that was the issue would it be an intermittent problem?

 

Yes, especially after the brakes are hot. Change the fluid every two years.

 

Ive never changed the brake fluid on any of my cars unless changing out the calipers. Never had an issue. Maybe I just got lucky.

Earlier this year I drove a brand new 2016 Scat at a dealer. Came back from the test drive and and noticed the brake peddle all of a sudden went to the floor. Felt the the master cylinder gave out. Sure enough, dealer called a few days later and said the master cylinder had to be replaced. Might be worth checking out if a brake fluid flush and fill doesn't help.

 

Correct--if the fluid flush doesn't work then the master cylinder is likely at fault. However, when a master cylinder fails it is not normally an intermittent problem, just a big all the time problem!

 

That is true.

 

I've had master cylinders fail intermittently. They will seem fine most of the time, but with certain pedal pressure...right to the floor. Release it and/or pump it and it comes back to normal.

It's usually the result of the piston seal failing, catch it just right and the seal folds and the pressure bleeds by.

If I feel it just once, it's new master cylinder time.

I wouldn't waste any time trying to just replace the fluid and see if it works. A new master cylinder is cheap compared to having no brakes at a critical moment. You can always change the fluid while you are doing it.

 

I concur...why chance it?

 

Our 2013 Dart had a similar problem with the clutch master cylinder. It had a seal that was bad and would occasionally fail to keep pressure. It started about a year after we had it. It was repaired on a recall notice and all is well,. but it makes me think that it may be a similar thing with your brake master cylinder. Perhaps over time it is starting to fail a well. It doesn't take muck to lose pressure.

 

Sorry I've been out for a while...New development on the brakes now. The problem is now constant, the pedal is very mushy. When I pump it up with the engine off it slowly sinks down. Master cylinder for sure? Battery just took a dump the same time the brake issue became constant. Unrelated? Replaced battery and brakes are still mushy.
On an unrelated issue having problems with the back up cam going in and out and the A/C recirculate not working. Any tips for those???

Trade in the car? I'd hate to do that as I haven't even done a burn out in it yet. Wife put new tires on it while I was out of town and I can't bring myself to destroy them.

 

Once again. As far as the brakes are concerned...

You need a new master cylinder. Replace it and the fluid and solve the problem.

 

Most definitely replacing the master cylinder. How do I flush the old fluid from the Lines? I want replace with synthetic but don't know how to purge the system. Is it as simple as bleeding out the fluid at the furthest point and work back to the closest?

 

Gotta love university of you tube!! Looks like I need to buy a mighty vac vacuum pump kit to bleed out the old fluid and air. This looks to be much easier then replacing the A/C clutch and pulley on my ford 6.0 w/o removing the compressor. Thank you all for your input, will let you know how it works out. UT is playing tomorrow and I still haven't located the new part so it will probably be next weekend before I get to this. Thanks again for the help!

 

I wouldn't bother with synthetic brake fluid. Just do DOT4.

 

DOT 4 is synthetic... I think you meant the troublesome Silicon fluid that race cars use (doesn't work well on the street, too hard to get all the air bubbles out of it).

 

No, actually I was unaware that all DOT4 was synthetic. Learn something new every day.

 

Got the master cylinder replaced. Here's the weird part, Bled all four wheels and got all the air and old fluid out. Went for a test drive and the pedal was still mushy. Decided it was time to trade in my broken car and I could now ruin my tires. Turned off traction control and ripped out some donuts. I'll be damned if the f@#$%^*g pedal didn't firm up! What the hell? The next day my ABS light and traction control light came on for all of two minutes then cut out. Dirty sensor? Any ideas why the pedal would stay limp then firm up? Haven't had any issues since then...

 

Solved mine...Had the same problem..no fluid leak..and no errors codes ...pedal to the floor.
It happened at idle or down shifting and worse intermittent..I thought it was
a vacuum leaks so i replaced hose.. nothing found..until I learned hemi
have an issues with gaskets in the intake manifold...so I tighten the bolts
and it went away for months until it came back...so I bought new gasket
and spent 4 hours changing them...and you can’t tell unless you remove the gaskets.
And one fell apart...Bingo