355 Brakes ineffective after driving spiritedly

If the pedal is stiff but you are not getting retardation, the pads are the likely culprit.
{I had such an event on the race tracks and had to "leave the paved surface" even with fresh (3-day old) brake fluid.}

In my case, the <front> pads taken out of the calipers looks like wood that had been eaten by termites.
Higher temperature pads (Ferrodo DS2500) solved the track temperature problem.

A fluid loss (or boiled fluid) would not result in the brakes "coming back" after a bit of cooling.
A failure of the vacuum pump would not result in a stiff feeling pedal.

 

I would try to get your car into a shop. To me, that sounds like a clog if the pedal was very hard and you weren't getting braking. If the pedal was working normally, I'd suspect that your brakes were glazed over or not bedded properly... or that you chewed through the pads, but you ruled both these out in your description.

Good luck, this one seems a bit dangerous.

 

Gelled clogged fluid?

 

brake booster circuit

 

Fail safe on the ATE Teves anti lock system is to revert to normal passive braking, which could explain the difference in pedal feel, until it kicks back in.

Not sure about the Bosch version but imagine it is the same.

Sounds like glazed pads though, that is the easiest first course of action to resolve initially.

Fluid loss/airlocks would result in a spongy pedal and the abs pump kicking in constantly.

 

That's why I said booster circuit. If your post is accurate that's not glazing because glazing does not come back. Once glazed pads are done.

 

Do you hear the abs prime on start up? and the pedal having a pulsing feel? system failure is usually a seized pump or a faulty sensor, usually attributed to a nick in the loom somewhere or water getting into the joint where the sensor attaches to the loom.

You can attempt to get the glaze off the pads with a palm sander and a low grit pad, but given it is a cheap option then replacement is best, win win really as even if this turns out not to be the cause you have fresh pads and one less item on the list of possible causes.

 

The pump should sound like a servo motor at start up until the system is pressurised then switch off. I am going off another car equipped with the same system so have to assume the 355 operates the same way, hopefully a current owner can confirm for you.

Is yours a ATE Teves or a later Bosch car?

 

If your calipers are sticking it can cause the pads to overheat even without hard braking.

 

The clutch is on a separate circuit, it does not share fluid with the brakes.

There is probably enough fluid in the braking circuit to allow the pump to keep sufficient pressure to provide a solid pedal, but that pump is working overtime in order to do so, and will burn out as a result, time to top it up and that will allow the pump to prime and then switch off, if it then loses fluid again, then yes you have a leak/s

 

When was the last time the brakes were bled? I would start by thoroughly bleeding the system with fresh fluid and checking for leaks - the reservoir being low and pump running extra are major red flags that you have a fluid leak somewhere - unless it's been a really long time since the system was bled.

I've overheated the pads before on track but it took threshold braking from very high speed (140+mph), and street driving should not stress the brakes much unless you're driving like a total lunatic. I moved to Hawk black pads - they generate a lot of dust but are easy on the rotors as those are a lot more expensive to replace than the pads.

 

No brake warning light?

 

Yeah, why take a closer look at puddles of fluid under your car, just drive and enjoy, probably nothing

 

There is a brake line coupler in that area that is disconnected when removing the engine cradle. May be leaking there. However your other thread referenced leakage above that area. Perhaps there are multiple leaks.