PMB 914-6/GT - Rear Calipers

[davep]

With that arrangement of inlet and outlet on the same side (the inner side), how does air get bled out of the outer side?

With great difficulty! Mostly high pressure to squeeze the bubbles into tiny bubbles, and a rubber hammer to get them moving. Lots of bleeding until the pedal is nice & hard. Note: the 914 rear calipers are very difficult due to the internal mechanism which can trap bubbles, however the basic principle applies to all calipers that do not have bleed nipples on each side of the caliper.

[gridgway]

I've always used a hard hammer to get the bubbles off the internal faces and mechanisms. Perhaps I'm just too brutal

[glovebox]

And any update on the problem of leaks Mark?

Graham[/quote]

Apparently new seals and bottom tap are in the post???!

[gridgway]

hope that solves it. I uprated the front brakes on my subaru once and that involved fatter discs, splitting the calipers and putting spacers in. I thought it would never work, but it was good first time, so maybe it's not that hard to seal calipers after all!

Good luck!
Graham

[Mr Pharmacist]

I stripped my 914 calipers and rebuilt them and never had any hint of a leak. I think its fairly straight forward as long as you are careful

[glovebox]

Yeah me too! Stripped completely front and back ! Never leaked in the last 6 years ! [FLUSHED FACE]

Until now !

[glovebox]

New seals and bottoming tap arrived today

[gridgway]

All back together now?

[glovebox]

All back together now?

Ha ha not quite

First thread shows promise

[gridgway]

Interesting. How does the tap work then? It's just cutting the thread? How does it not damage the seat? And how far down does the thread need to go?

[glovebox]

Interesting. How does the tap work then? It's just cutting the thread? How does it not damage the seat? And how far down does the thread need to go?

I'm sure theirs far more qualified guys on here to answer that. But yes it's cutting more thread. So the thought is at the moment the bleed valve is not bottoming out the seat. So this should allow this ??

Regards Mark.

[Bruce M]

"First cut" taps have a taper which gradually cuts the thread and is less likely to bind or cut at an angle. The bottoming tap cuts the full depth thread much closer to the end of the tap (needed in a blind hole).

[gridgway]

So I guess with some measurement, it's easy to see if the thread is deep enough.

[glovebox]

And also when the calipers split into two you can see from the back side. Or at least get a good indication.

[gridgway]

How close to the sealing face does the thread need to go?