Am I supposed to turn the car on when I bleed my brakes?

 

Ignition on with the engine off is required of suggested for most cars with ABS brakes.

 

Thanks. But found out my calipers are out

 

Car off, key off for most cars, not sure about Lexus but some older GMs with 1st gen abs need a special procedure.
What does "my calipers are out" mean?

 

car off..key off. if u run the system dry with the key on ur screwed.

 

Is it even safe to bleed these cars ?? I mean, given our 15 - 20 year old boosters

 

Why would the booster be a concern?

 

booster only works when the car is on. it's the master cylinder that does all fluid transfer as well as the ABS module.

calipers out meaning they are stuck or seized i assume?

 

sry guys, I meant Master Cylinder

 

lol if it wasn't safe to bleed what makes you think it would actually work at all?

 

If the fluid in the master reservoir is black and is loaded with gunk, sure you may have issues bleeding your brakes, because of such poor maintenance habits of you and/or PO(s).

Pumping that crap through a master is a good chance of damaging seals.
Additionally, such crap in the reservoir is also an indicator that there is a good chance of corrosion/pitting on the master cylinder sleeve. this is an issue when bleeding as full stroking the master will often drag the seals over the rough sections outside the normal stroke and rip up the seals, resulting in a bypassing master.