Brake Problems

If fluid isn't exiting the system, this is a bad sign for the MC internal seals (regardless of the electrial failure light -- which I think is just a natural consequence if the forward chamber of your MC isn't working properly).

 

Either you still have some air in the system that you cannot get out, or the brake master cylinder is defective. Have you tried pressure bleeding the system while having someone pump on the pedal? If you have pumped a quart of fluid through the system, and it comes out clean with no air from all of the bleeders, then I would say that your brake master cylinder has a problem.

The next step would be to remove, disassemble and inspect the master for damaged/worn seals or corrosion in the bore.

 

Bob,

The system on the 308s is a very basic system. It's not like you've got ABS or dual masters, or anything like that. There are only a few things that can cause that symptom. First, you can have a leak somewhere. You say that nothing is leaking, but double check each wheel to be sure and all fittings. Also, check to be sure the pads are not excessively worn down, as this will increase pedal travel.

Next, it could be air in the system. I would recommend doing a very careful bleed, the old fashioned way: Make sure the reservoir is topped up; have someone push the pedal for you; start with the right rear, left rear, right front, left front, bleed each corner. Have your helper push on the pedal, open the bleeder, as the pedal nears the floor, close the bleeder. Repeat a few times to be sure there are no air bubbles, and close the bleeder as your helper is pushing the pedal down for the last time. Do all 4 corners that way, topping up the reservoir between each wheel. The pedal should be nice and firm.

If you STILL have a sinking pedal, IMHO it can only be one thing -- the MC seal. Even though White Post just did it for you, it is possible the seal has gone bad, especially if some dirt or corrosion got in the MC and scored the seal. The MC is easy to rebuild, and change the seal yourself if you want to give it a go, assuming the cylinder itself is in good condition and not corroded or scored.

 

Its possibe that the brake fluid may be leaking into the brake booster.I found that out the hard way as well

 

That's true, but if he is not seeing any loss of brake fluid from the reservoir, leaking into the booster probably isn't very likely.

 

I vote for air in the system. Dragracer don't use brakes what does he know? Just kidding. 5 ways the wrong way does no good. I have noticed the threads on Ferrari bleed screws are poor. They allow air in as you bleed sometimes if you open them too much during a bleed. quarter turn is all you need. Some calipers also have an inside bleed screw so you have to take the wheel off to bleed well especially if you sucked air the first time by allowing the reservoir to get too low with the motive bleeder. Under those conditions you may have to prime the master and then bleed at each wheel two man style no motive! You will need to now move air all the way from the master! Also you can trap air in nooks and crannies and not purge the air in a slow constant pressure bleed. Try this trick at the right rear first. Tell your buddy to pump pump pump and on the forth pump he goes to the floor and holds there and you crack the bleeder 1/4 turn on the count of 4 at the same time. The momentum moves the air/fluid fast and sometimes you will be greeted with a blast of air and fluid. If you get air after doing this a few times you know what's wrong. Air! This trick also works great on clutch purges. A master seal is possible and you can diagnose it by severing the master outputs and screwing in a plug. If you press the pedal and the pedal moves you got a master seal blown up. If it is rock hard you still got air in your lines down stream. Before you do this make sure to purge air in the master by making a loop from the master outflow to the master reservoir and pump it up a few times until you get good flow. Then all the air will be out of the master and it can do its job. This is why it is so important to make double damn sure you don't suck air at the master when you bleed. I have seen this and fixed this issue too many times to count. Good Luck!

White post does a good job BTW and should last longer than 2 years easy. heck the seals in your calipers could be be 20 and are probably fine.