rear brake piston question

[fiatjack]

So....disassembly of the rear calipers is complete. I'm starting with the passenger side and noticed the little channel showing the orientation of the piston is not on the face like in my shop manuals. Anyone experience this before? Do not want to continue anymore if I'm never going to be able to bleed them correctly. Any help would be greatly appreciated.

[18Fiatsandcounting]

I believe the correct orientation is with that scribe line facing up when the calipers are on the car (above the protrusion that pushes against the inner brake pad). I've always done it this way, and I've never had any problems bleeding the rear brakes.

-Bryan

[fiatjack]

Thanks Bryan, unfortunately i dont have a scribe line. I'm not sure how to add a photo here but could email one offline if needed.

[18Fiatsandcounting]

Hmmm... Some aftermarket pistons/calipers do not have that scribe line. If the piston is removed from the bore, you can see that there is an additional cavity on the inside of the bore. That cavity should face upward, and the scribe line (if it were present) would correspond to the side that the cavity is on. Presumably the cavity is there to allow air bubbles trapped inside the piston to be flushed out during bleeding.

If you look closely at the picture in this link, you can see the scribe line (click on the picture to see an expanded view). Basically, it should face the bleeder nipple.
https://www.midwest-bayless.com/p-19308 ... l-new.aspx

If it were me, I'd screw out the piston and mark on the face of it where the inside cavity points. But, since you have a 50/50 chance of having it right, you could try bleeding the brakes. If it seems OK, I wouldn't worry about it.

By the way, that channel in the piston face should be level with the ground.

-Bryan

[davefrancisco]

Does this mean every time the rear brakes are bled that the line on the piston needs to reset? Meaning aligned at the top?

Thanks

Dave

[18Fiatsandcounting]

The piston in the rear calipers moves in and out, but it shouldn't rotate (It's held in place by a nub on the brake pads). So, once you set the scribe line to the top, it should stay there. The adjustment for the handbrake happens internally inside the rear pistons. You can bleed the rear brakes as often as you please and the piston scribe line should stay put.

Hope that helps clarify...

-Bryan

[davefrancisco]

Thanks Bryan... The answer I was hoping for.

Dave

[davefrancisco]

Thanks Bryan... The answer I was hoping for.

Dave

[davefrancisco]

Thanks Bryan... The answer I was hoping for.

Dave