Over the weekend, I put my car up on stands for the task of pressure-bleeding my brakes/refreshing the fluid. Initiated the process with the usual sequence of RR, LR, RF, LF...

I have a combo offset 10/11mm wrench I brought over to the right-rear caliper to start, and needed the 11mm side of the wrench to loosen the bleed screw. So I bled that brake and moved to the left-rear, where the bleed screw needed the 10mm side to loosen... On both the fronts the bleed screws required 10mm as well.

I assume that someone, at some point replaced the bleed screw on my right-rear caliper with this larger 11mm screw -- and this is not the way the car was equipped as new?

Would this indicate that the original bleed screw was broken at some time in the past, and the hole tapped larger for the screw that took an 11mm wrench to loosen?

It's not a big deal, as the larger screw functioned properly -- it's just an oddity I discovered in the process.

Also, I'm going to throw in a recommendation for the ECS/Schwaben 3-Liter European Pressure Brake Bleeder. It's the best designed unit I've seen, with solid connections and the separate pressure-release fill plug that made the chore extremely easy and neat.

 

It could be that the bleed screw was replaced and just have a bigger head. They can get plugged up pretty bad and an errant wrench can close the hole off.

 

The John Cooper works cars use 11mm in front and 10mm in back, so it really doesn't matter, they will both work fine.

 

Is it the case that the portion of the bleed screw that threads into the caliper is the same thread pitch irregardless of whether the 'nut/wrench' size is 10mm or 11mm?

 

Most likely. Replacement screws can have different sized hex heads on them but the same thread size.

Most likely the head of the original one got rounded off and the replacement came from napa or somewhere, same thread, different hex.