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Let me start off by saying yes I know how to bleed brakes.
Now that that's out of the way, here is the issue I'm coming across. I have an S4 GTU, and am in the process of rebuilding the entire braking system. I have the calipers off the car, and have just rebuilt those. I noticed on my rear calipers, I have 2 bleeders. Everything I've ever worked on has 1 bleeder in the rear, and all the FC documentation i can find, even from Mazda, only mentions 1 bleeder.
Is this a T2 thing, since the S4 GTU's came with the T2 accessories? How do I go about bleeding this? Thank you in advance for any advice
The top bleeder screw is used for bleeding the air out of the system, and the bottom bleeder screw is used for replacing the brake fluid.
From the 1986 Mazda FSM, page 11-11:
"Rear brake:
After brake fluid replacement:
Bleed air by using the upper bleeding screw.
Air bleeding procedure is done in the same manner
as air bleeding of the front brakes."
The top bleeder screw is used for bleeding the air out of the system, and the bottom bleeder screw is used for replacing the brake fluid.
From the 1986 Mazda FSM, page 11-11:
"Rear brake:
After brake fluid replacement:
Bleed air by using the upper bleeding screw.
Air bleeding procedure is done in the same manner
as air bleeding of the front brakes."
Gotcha. So in the above picture, "upper" is the one on the left, correct?
It also states:
Rear brake
After dissembling the caliber:
Bleed air by using the lower bleed screw
Air bleeding procedure is done in the same manner
as air bleeding of the front brakes.
I always use my Motive pressure bleeder to bleed the brakes & replace all the fluid in the system with fresh fluid. When doing the T2, I use that bottom bleeder screw on the rear calipers first to purge out all the nasty old fluid in the caliper/lines, then close the bottom screw and bleed the air out of that rear caliper from the top bleeder screw.
It also states:
Rear brake
After dissembling the caliber:
Bleed air by using the lower bleed screw
Air bleeding procedure is done in the same manner
as air bleeding of the front brakes.
You're right. It does mention that too.
Kind of odd because air will always rise to the top.
Alternatively, my '89 FSM (electronic copy) mentions nothing about the two rear bleeder screws.
I always use my Motive pressure bleeder to bleed the brakes & replace all the fluid in the system with fresh fluid. When doing the T2, I use that bottom bleeder screw on the rear calipers first to purge out all the nasty old fluid in the caliper/lines, then close the bottom screw and bleed the air out of that rear caliper from the top bleeder screw.
That's the same way I've been doing it but with my Mityvac. Never had any issues.
04-17-23, 02:47 PM
