355 Loss of brake pressure while driving

Pads,
fluid on pads,
fluid on rotors,
a qualified mechanic.

 

Sounds like a master cylinder.

 

What year is the car? the Teves and Bosch are very different systems with different failure modes.

Initial symptoms do sound like classic overheated brakes (possibly from partly engaged parking brake), but the fact that they didn't come back when they cooled suggests there is another problem...

 

It seems that your brake fluid boiled causing the sinking of the brake pedal. This especially happens if the brake fluid has absorbed a lot of moisture which significantly lowers the fluid boiling point. When did you last flush/replace the brake fluid in your 355?

 

Sounds like you need a bleed at minimum. I'd be doing a complete flush if the fluid is over 1 yr old. When it gets hot the soft pedal might return. Overheating rears with parking brake and having to limp home with sketch brakes seems weird. You did not boil fronts you should have braking. More typical is boiling front brakes from heavy driving. We see that under track conditions all the time but it should never happen at road speeds.

 

Motul RBF 600 (or 660) is a racing brake fluid. The advantage of a racing brake fluid is that it has a high boiling point (when fresh). However, this fluid will absorb moisture faster than the standard brake fluid so, in order to keep its boiling point high, it needs to be flush-replaced more often. I would do it every 6 months or so.

 

Don't you have a red indicator light on the dash that lets you know when the parking brake is engaged? I have one on my 3.2 Mondial.
Alden

 

At the very least bleed the brakes. You have compromised the brake fluid at the caliper level from overheat and boil. Call you mechanic and tell him your story. It's a safety issue.

 

Parking brake on the 355 uses shoes inside the drum and do not use any component of the service brakes. Parking brake left on isnt going to affec the service brakes.

 

Yeh , ( 348 owner here same set up brake wise ) I am struggling to grasp too how the shoes can heat the rotor enough moving only a few miles as reported.
They either jammed on functioning, or loose letting the wheel roll .

If they do stick , let’s call it that then all they do is create a bit of black dust ( blows out of the adjustment hole and maybe squeal a bit .Granted the engine noise might drown the squeal?

Not convinced the heat generated by a sticky shoe is enough to be transferred through the pads , heat the metal mass of the callipers to boil the fluid .
As said if the hand brake wasn’t released the car wouldn’t move you would notice it .

As far as the light on the dash …..vue a ability depends on the steering wheel position and size of the guy driving .
Also the switch ( at the rear of the handle hidden away ) is a bit fickle .

The son probably doesn’t know how to use “ on the fly handbrake s “
You have to push the button in , hold it in all the way as you lift up to release and still hold it in while you drop it down .
If you accidentally take your thumb off the button on the down stroke the light stays on and sometimes depending how far you got the handle down , the shoes don’t properly release . They stick a bit .

Aston Martins are the same btw .

There’s a knack to operating “ on the fly “ handbrakes / parking brakes .

Possibly if you do a 300 mile tank emptying high speed run circa 100 mph + for 3 hours in one stint - then ok partial engaged shoes might just heat up enough to vaporise the brake fluid . I get the theoretical potential. But this wasn’t this type of drive .Assuming you didn’t notice the dash light mind !