ABS light slow to turn off

The time for the ABS light to go off is the time that the ABS electric pump needs to fill-up the pressure reservoir (the pear shaped thing attached to the pump). This time can vary a lot depending on:

1. Whether you turn the key to the first position and pause for a while before turning the key to ign. & start (the ABS pump starts running as soon as the key is turned one click). The longer you keep the key in the first position, the shorter the time for the ABS light to go off after the start-up.

2. Whether you press the brake pedal after you have switched the engine off. Each press will release some fluid from the reservoir and it will later take longer for the ABS pump to re-fill it.

3. The system might have developed a slow internal back-leak of the fluid under pressure in the reservoir causing the reservoir to empty itself over a longer period of time so, every time you turn the key the pump has to fill-up the empty reservoir (longer time). A slow back-leak will not be a problem to the brakes as long as the ABS light stays off and the brakes feel good.

In any case, check the short high pressure hose connecting the ABS pump assembly to the metal brake pipe for any leaks.

 

When did you last change the brake fluid?

My 348 used to do that until I had cause to do a complete fluid change/bleed brakes. Drasticly reduced the time for the light to go out which I put down to a bit of air in system.

 

Thanks so much for the details.
I find that in my 348 the abs light can also take a while to go out when I start it for the first time after a few days. If I turn engine off and start again it goes out much quicker. Sometimes even after an hour or so it's still much quicker.

 

Mine also takes a little longer if not used for a while but taking an hour is definitely not right.

One of the other symptoms I used to have before the fluid change was that the ABS light would randomly come off and on.

I'd do that first as a bttle of fluid to do it yourself is only about £10

 

Something else to check out:
http://www.ferrarichat.com/forum/348-355-sponsored-bradan/360495-abs-brake-accumulator-101-a.html

 

Great information, thank you also.

I too was wondering about this. I hadn't yet formulated a theory as to when it took less or more time for the lamps to go off. Now you've provided some parameters I will do some testing myself.

 

Pressure accumulators were also used on BMW's in the 80's and failed often. The symptom was a very hard pedal. You still had brakes, but the pedal was very hard. Maybe they added a pump to the system as a backup to a failing accumulator?