Brakes lose pressure over night?

[wander2039]

Recently replaced the MC on the Festiva because of all the obvious symptoms. One problem remains though. Sometimes when it sets over a long period of time you won't have any brakes unless you pump it or just start the car. After that it's fine. Drove it in Branson on all those hills and the brakes were solid the entire time. No fluid leakage and fluid level hasn't changed. Any idea's? It's almost seems one of the calipers are decompressing.. not sure how that's possible.

 

[40Deluxe]

Does it feel like the power brake booster has lost it vacuum?Or is it an actual pedal going down to the floor feeling,if the pedal goes to floor then it is a hydraulic problem,and would suspect the master cylinder,did you bench bleed the master cylinder before install.

 

[wander2039]

The pedal goes pretty much all the way to the floor. I bench bled it along with bleed all four sides. This first MC I got was bad. This one I installed in under an hour. The other worked on it over 8 hours and wouldn't do anything. If it does need to bleed again why is it working fine otherwise?

 

[MrBeachcomber]

All this is a shot in the dark because you need to describe the problem more fully, i.e., how long does the car need to sit before the symptoms occur, does the brake pedal go to the floor, do you have a vacuum booster, have the calipers ever been rebuilt, etc.

Given the above, try marking the fluid level in the master cylinder. If you're not leaking fluid, it sounds like air in the system that needs to be compressed before "normal" braking occurs. Did you bench bleed the master cylinder before installation? Did you bleed all four brakes after the installation?

I've had this type of problem before on both my '67 and '72 Corette; and my suspicions are that the seals on the caliper pistons are shot and allowing air to enter the calipers after the brakes have been applied. Hope this helps.

 

[40Deluxe]

Where are you getting the master cylinders at?If all else fails try a motorcraft master cylinder,How do the pistons react to being compressed in the calipers?Can you move them back into the calipers easily with a c-clamp?

 

[Cause4Alarm]

a leak somewhere else?

 

[mechtech2]

From what you describe, it may be drum brakes that are too far loose and out of adjustment.
They need to be pumped up to get to where they should be.
If you booster was leaking, the pedal would rise up and be hard.

I am not ruling out some internal hydraulic part that is faulty/leaking.

 

[wander2039]

Not sure on the rear brakes but if you go by the emergency brake they should be adjusted right. The MC is from OReillys the first one was from Autozone. The calipers on the front are fairly stiff. Didn't use a c-clamp only a big pair of pliers. No leaks.. I'm positive on that compared to the Aspire it has a visible leak but holds pressure fine.

Beachcomber you might be on to something. When I was messing with the first MC I used the drivers front caliper to see if I could get it to bleed properly. Granted it was defective but every time you'd apply pressure it would come out a little and draw back in. With the next MC it didn't do it so didn't much of it. I have greased all the pivot points on all the calipers but on that particular caliper one of shafts for the bolts is rusted so it's a bit tighter. It can still slide some but it's not as free as the other. Soundss like I need to replace that caliper but it only does it once a week or every 2 weeks... probably wait till it gets worse.

 

[unDummy]

Bleed again. If you vacuum bled, pressure bleed. If you pressure bled, vacuum bled.

 

[sciphi]

The power brake booster I had go bad on me let the pedal travel right to the floor with zero braking power, just like a bad M/C. Disconnecting the brake booster and depleting the vacuum let the brakes function again without power assist. I went through a M/C and several brake bleedings before twigging to the brake booster. A replacement solved my braking issues.