Have a few questions some of you may have answers to. Renewed the brake fluid on my TS V6 on weekend. Some (not all instructions tell one to have engine running on cars with ABS). wHY??? The cap on the brake fluid reservoir has black rubber bellows. Anyone know why? Td

Have a few questions some of you may have answers to. Renewed the brake fluid on my TS V6 on weekend. Some (not all instructions tell one to have engine running on cars with ABS). wHY??? The cap on the brake fluid reservoir has black rubber bellows. Anyone know why? Td

I think it helps for the following reason.
If the engine is running it helps to circulate the brake fluid out of the tiny capilliary lines to and from the ABS unit. It helps to fully flush the system out.