how come the engine has to be running while bleeding the brakes?

[Kiiii]

i've looked at the repair manuals for the eclipse 90-99 (NON ABS) and it says to start the engine and bleed in the sequence they've stated.

i've heard that its okay to do it without the engine running but i'm wondering why does the engine have to be running while bleeding the brakes? WTF

thanks in advance..

 

[whe3ls]

vacuum assist brakes, with out the engine on there isnt any vacuum

 

[MidShipCivic]

You don't have to do that, you can bleed them normally with the engine off.

 

[Kiiii]

well then its killing me to know why mitsubishi stated in their manual to have the engine on..?

 

[MidShipCivic]

What manual are you reading from ?

 

[Deuce_three]

i always bled my cars with the engine off.

 

[Kiiii]

the official service manual of mitsubishi
this information was also in all data

 

[concreteTSI]

im a mechanic and its rare we start cars to bleed brakes. With the engine off it doesnt have the vac. assist which makes it a little easier to push the air out, atleast makes it easier to feel in the pedal. But in rare cases we may have trouble and the pedal will feel good with the engine off but with the assist its soft and sinks, in that instant we may bleed with the car running to help determine if there maybe a booster problem

 

[MidShipCivic]

i always bled my cars with the engine off.

If you turn the car on its vacuum assisted booster as you bleed the brakes the pedal will get harder, however I never have issues with completely getting clean fluid coming out.

You can leave it off.