Brakes No Bueno

[Jp-oh]

Hi. I was driving along recently and NEEDED some hard braking and was disappointed to find the brakes were way less effective than I expected. They slowed me mostly but felt spongy and would not even come close to locking. This is a new symptom as they previously worked as expected. The brakes would not have been close to hot so not fade.

A few months ago I repaired the front calipers and put new rotors and pads on the front.

I also find the brake light comes on only after a bit of pressure and pedal travel. I have not noticed the pedal gradually going down if I leave my foot on with light pressure but the top inche of pedal travel is light. Pumping doesn't seem to build up more pressure.

I have good fluid level and haven't found any leaks.

Master cylinder?

[Drisump]

Was it the first drive of the season? Heavy rust on discs will be slippery. Also if you haven't allowed a bedding in time for the new pads to conform to the discs they will likely "underwhelm". If none of those concerns are pertinent, investigating the MC would likely be my next move. These are very simple systems. No ABS, no traction control. If the pedal is not generating proper stopping force, the pedal doesn't feel hard (servo problem), all pads are good and no evident external leak it seems internal pressure leakage is likely the culpit. Cheers

[RedCoupe]

Yes, an internal leak in you master cylinder can cause a loss of pressure in the front brakes and reduced stopping power. But, how old are the flexible brake hoses? Brake hoses that are old and starting to soften can swell under pressure and reduce the amount of energy sent to the calipers.

[Jp-oh]

Not close to first drive, brakes have been great for months. This is a sudden onset symptom. I was going to pull of the wheels and check the lines and maybe do a bleed for good measure. The lines are original as far as I know.

[fanaudical]

If the rubber brake lines are original it's time to change them.

You might also look for any signs of contamination on the pads/rotors. Sometimes some road spray can carry some nasty stuff with it (oil and such).

[Reiver]

30 year old rubber brake lines would be the place to start...they can swell internally over time. One of the first things I change out on a used/PO car...always.
Since you'll be bleeding the system check around your booster area for fluid too.

[Joe Bob]

If fluid level is consistent then the next fix is brake lines. Flush fluid system as well.

[Jp-oh]

I'll do the lines and bleed first. Any use in braided or just go Porsche parts rubber.

[Joe Bob]

Make sure the braided lines are the DOT approved ones. Most racers replace them after a season of use.