I feel that I have to share this...
few months ago I was replacing brake lines and it was quite a pita to bleed air out. Left caliper never really showed good flow no matter how much I was pressing the pedal so I blamed caliper age and decided that I will replace them.

Today I was replacing calipers. After replacing left one I got the same problem - no bubbles and literally no flow out of bleed nipple. I checked all pipes to caliper, and I placed match between brake pads to see if there is pressure - it got smashed so fluid is getting into the caliper with pressure.

Completely confused, I took second (new) caliper and studied it. Took out bleeding nipple and pumped air into feeding hole - no air was coming out of bleeding hole(and pistons flew out). I figured there must be some sophisticated valve in the bleeding hole that only opens at high pressure.

I took old caliper that I removed from my car, did the same thing but this time I took a piece of wire and poked into the bleeding hole. After some heavy poking the wire went into the hole good 1.5 inches!!! It turns out my old caliper had clogged bleeding hole. Now if I pumped air in - it was happily escaping from the bleeding hole (making fountain of rust and dirt from wire poking).

Now I took wire to new calipers - both had bleeding holes completely clogged!!! I could not believe it. One of the calipers was obviously painted and paint was in the hole. I actually had to use drill bit to open that hole, which took a while.

After 'drilling' the holes - bleeding brakes was piece of cake.

As I was searching this forum for advice it sounded like quite a few folks here had problem bleeding brakes.

My advice now - unscrew bleeding nipple out and poke with wire into the hole. It should go in good1.5 inches (from the bottom of the opening).

 

Well found.

Never had that issue, but plenty of goo when I 1st did the "catch up", then annual fluid flush, good as new.

Gotta luv slack precious caretakers.

 

Never had that problem as my New Brake Calipers always come complete with Brand New Bleed Nipples



New Calipers for my XJS 'Nothings Too Good For My Baby' (copyright 'Greg')

 

Mine looked exactly like yours. When I unscrewed that "Brand New Bleed Nipples" the hole behind it was completely clogged and that yellow paint that make caliper look like new was in the hole as well.

 

Thanks for posting that. Its one of those multitude problems that no manual will cover.

 

Was it rebuilt? Thats what we all fear- an improper rebuild job where mostly they are painted and maybe a piston seal replaced but no real consideration to the functionality. That crap may have been the reason the first guy replaced it too