DOT4 Brake Fluid Change and ABS
 

After a move last year, I don't have many track/race experienced mechanics in my area, so I thought I'd ask about changing brake fluid.

I need to change the stock DOT3 fluid to DOT4 fluid for the track. My mechanic did not know if the FR-S required a release of the ABS system to completely flush the old DOT3 fluid. Does anyone know if this is an issue? Does the clutch need to be cycled at the same time because it uses the same fluid and reservoir?

Wait wut?

We just did a "normal" bleed and we've been fine... I wasn't aware there were extra steps (and if they were taken, I'm unaware of that as well)

A normal bleed will suffice. DOT 3 and 4 don't have any harmful interactions with each other. I don't happen to know if the clutch uses the same reservoir though.

Edit: I see what you're asking. I believe someone posted a pdf of the factory service manual, this question should be answered in there.

I have seen this before but only on older cars (90 300zx and an early c5 vette). Those ABS modules looked very different than the one in our cars though. I searched around and couldn't find an answer so I just did a normal bleed. If you do find out let us know. And the clutch and brake cylinders are separate so you can drain the brakes without affecting the clutch.

It should be in the manual. On even recent Subaru ABS models it was sometimes necessary to cycle the ABS pump to properly bleed the brakes, although I never ran into issues with not doing it on my WRX.