[Woody '04]

I came across this when searching for something different.
http://www.endwrench.com/current/summer02/brakefluid.pdf
I also see it has been mentioned a number of times in this forum.

Does anyone know why Subaru recommends a different bleeding order than what is traditionally done? Traditionally you start farthest away from the master cylinder and then do closest first.

For many cars it might be:
1) Passenger Rear
2) Driver Rear
3) Passenger Front
4) Driver Front

Subaru Recommends:
1) Passenger Front
2) Driver Rear
3) Driver Front
4) Passenger Rear

I'm sure many Subarus have been bled per "standard procedure" rather than "Subaru procedure" over the years. I can't help but think that if it would cause any damage or operational issues there would be many more posts about the topic.

 

[philbytx]

Subaru's split circuit braking system

Could be because of the Subie dual braking circuit set-up.
I use the "old style' method on my 1995 BMW E34 and the Subie system on the Foz. No probs with either....

 

[BAC5.2]

I think many cars have a parallel-redundant braking system, where if the driver front brake fails, both passenger side brakes still work.

Subaru's use cross-redundant braking, so if the drivers front fails, you have the passenger front and driver rear still operational.

I believe the "bleed order" comes from how the ABS unit mixes fluid.

 

[funkymonkey1002]

Its because the master cylinder has 2 different circuits which are separate through the ABS unit as well. You'll see 2 hoses on the master cylinder and then "MC1" and "MC2" on the ABS block in line with the corners they feed. Each circuit does diagonal corners. IMO it probably won't make much of a difference what order you bleed them in.

Also, the service manual says to cycle the solenoids in the ABS unit when bleeding the brakes (can only be done if you have a subaru select monitor), which most people don't do.

 

[Woody '04]

well, that makes sense. it's hard to tell the exact plumbing from the diagrams. i was thinking about looking at it pretty closely the next time i bled things.

i'll have to review the manual. looking at the endwrench article linked, my impression was the stuff associated with the ABS unit was a test procedure, separate and apart from the bleed procedure.

 

[funkymonkey1002]

well, that makes sense. it's hard to tell the exact plumbing from the diagrams. i was thinking about looking at it pretty closely the next time i bled things.

i'll have to review the manual. looking at the endwrench article linked, my impression was the stuff associated with the ABS unit was a test procedure, separate and apart from the bleed procedure.

I just looked again at the service manual. In the periodic maintenance section on brakes it says to just bleed them, in the service section for "air bleeding" the brakes it calls for doing the ABS cycling. Interesting.

The plumbing is a little convoluted. 2 lines from the master cylinder goto the ABS unit, those are the MC1 and MC2 lines at the ABS unit, then on the ABS unit it breaks off into 4 lines labeled with which corner they run to.

 

[Northwest Tan]

Also, the service manual says to cycle the solenoids in the ABS unit when bleeding the brakes (can only be done if you have a subaru select monitor), which most people don't do.

I get around this by getting the ABS to kick in on a safe road. Then bleed the brakes again. :biggrin: