Rear caliper rebuild - any tips?

[thecolonel]

I was told that a mix of acetone and brake fluid
was good for rust removing and freeing off parts

[archigraphe]

Forgot to mention that whilst reconditioning a spare set of calipers one of them didnt even have a spring or dowel fitted!!

And how was blocked the piston body on the caliper? By rust, dirt.. Or with a hammer???

[VXdeMayo]

Dear Targa2000,
thanks for that really useful guidance, looking at my calipers you would never know that there was a spring down in the "innards". I think a lot of Plus Gas and careful digging might pay dividends! I will let you know how I get on this weekend. (I might well take you up on your offer of new dowels if I have to get brutal).
Why oh why did Lancia have to be so different!
best,
Chas and Anne.

[VXdeMayo]

Well the caliper piston have parted company from the yoke assemblies (at last). Got into the innards and things don't look too bad for 29 years and 85,000 miles. Rears have already been rebuilt apart from the handbrake cam (which is off at the platers). Fronts are proving a trifle more difficult as the inner sealing ring and rear piston have yet to come out. 70psi from a footpump will not budge the thin sealing ring, although the rear piston moves fine. (Yes I have taken out the sprung ring that keeps it in place). I think is's off to the garage to get them blown out!
Last lap approaching, then the suspension can be put back together as a unit.
Happ days,
Chas and Anne.

[lukasdeopalenica]

I also had found this operation hard, but eventually I dealt with the problem. I used a compressor and ca 8 Bar of air pressure to pressed out the inner (small or mixed circuit) piston. It is also essential to press the bigger piston back to its plase, to plug the hole that allow to build the pressure. Also both bleeding niples must be closed as well as the brake fluid inlet for bigger piston, and pressure is supplied to the mixed circuit piston. That worked well in my case 

[VXdeMayo]

Latest news from Somerset. The front calipers went off to my mechanic who attempted to blow the rear piston and parting piece out in stages (as the manual suggests). Well I know they were stuck but I could almost hear the language from here 10 miles away! I had obviously took the internal circlip out beforehand but boy they were tight. After two failed attempts with an industrial compressor and a couple of days soaking he manned up for the next attempt.
I think I did hear the explosion way up here in the Blackdown hills! So parts out but problem not quite over.
On inspection of the parting piece and rear pistons they are not in great condition, there is light scouring on the piston surface and the beginings of rust on the inner and outer faces! Note: I mentioned parting piece (x1)...... On exploding one of the parting pieces had sailed off into the rafters and went down into the waste oil tank!
 At least it will not rust any more....
I will post a request for a pair of pistons and parting pieces elsewhere.
Happy days.
Best,
Chas and Anne.

[VXdeMayo]

Guys, the latest!
so if there is a problem with the front calipers, I will try the back ones instead.
BUT:
Can anyone suggest a good way to re assemble the rear brake handbrake lever c/w cam and plunger. It's a s...d! The piston has been re assembled with new seals, everything is very clean etc, the book suggests "aligning the cutout on the top of the piston crown with the brake bleed nipple" etc.
So:
1) What is the piston's correct oreintation? The cut out on the top of the brake crown is parallel to a couple of machined lines. These obviously allow you to tell the correct position, but relative to what?
2) Once that simple alignment is made, and the plunger screwed down fully clockwise, how do you get the handbrake lever c/w it's cam in place whilst fighting the spring and the great upwards pressure from the plunger springs?
The book does suggest some sort of "G" Clamp, but there is very little to clamp down onto because the lever gets in the way!
I used to think I was quite handy but this has me beat!
I think Matt said he had done this procedure a few times.
Any advise will be welcome!
best,
Chas and Anne.

[MattNoVAT]

Chas,

Yes, I have done this a few times, sadly I have so much going on at the moment that I cannot recall the specific steps. Plus it was over a year ago that I last did it.  If it was sat in front of me I might stand a better chance, but everything is packed now.

What I do remember is that it took me a few attempts before I eventually got it right. I do recall being sat there with teh exploded diagram and the Haynes book of lies open while I swore at it on a regular basis.  Sorry I cannot offer any gems on this subject right now.

Once we are settled I have numerous sets of brakes to play with so I'll be able to refresh my memory.

[VXdeMayo]

Dear Matt and all,
Good news!
After my failed attempt at finishing the rebuild this morning I have now suceeded! I looked back over previous posts on this subject and there was some help but nothing specific, so while it is fresh in my memory I will attempt to explain so others out there will not curse (quite) so much.
(By the way, I think my first failed attempt was down to poor light, poor instructions, poor cold fingers and well... being a wus! (It was actually hailing outside my shed when I first tried this)!

However here goes!
1) Firstly rebuild the caliper with new seals and have piston in place with the machined slot in the crown aligned at 90 degrees to the cast flat sections which take the caliper irons. (The two machined lines on the piston crown should be above the slot when viewed from where the pads sit). Re-introduce plunger assy c/w spring washers etc and line up the plunger cam follower face with the drawing in the Haynes manual. (Note: you have to push & screw down simultaneously quite hard until it feels to have bottomed out).

2) Put in vice gripping on flat cast sections (assuming you have taken the iron yokes off first), with piston crown facing down and the lever bearing holes aligned so that you introduce the lever TOWARDS YOU. ( Nipple hole towards you). (This aides alignment vision etc).

3) Start to push in the lever so it just pokes out from the first bearing. Introduce the coiled spring and make sure that the spring "lips" align with the lever cut out track.

4) Slide the lever slightly further in to pick up the first "lip". Now with a small amount of grease introduce the cam at a slight angle downwards to try to engage with the lever cut out. (A small amount of upward movement on the lever will help).

5) With one hand and / or pliers hold the cam aligned with the cut out, with the other hand gently rock the lever further in towards you, picking up more of the cam on the way. Rock and slide lever to pick up second "lip".

6)Now re site the caliper block at 90 degrees to the first position (still lever coming towards you), gripping just a small part of each cast flat section. With a large "G" clamp and a small socket on the floating ball end (10mm 1/4 drive is fine or similar), gently compress the lever/cam /plunger assembly towards the piston crown. (The "G" clamp fixed end should rest on the piston crown). Do not overdo, but sight through second bearing hole to maintain alignment. You will now see the reason for changing the position in the vice, as this angle will give best view etc.

7) Utilising a second smaller "G" clamp, fixed end against the lever welded joint gently compress and push lever through second hole until bottoming out. Remove clamps and rock the lever all the way through so nylon washer butts up and reveals circlip track. Replace circlip.

Apply a decent amount of grease to all moving parts and replace rubber boot.

Job done. (I advise not using too much grease in the initial assembly stages as this will impeed the view for alignment later on. Just enough for initial lubing will do).

I hope that make some sort of sense. Now to tackle those front calipers (when I find the missing parting piece).
Best,
Chas and Anne

[mangocrazy]

I've just started the first steps in cleaning up and renovating my spare calipers. The front calipers appear (sort of) straightforward, but the rear ones look a bit complicated. I've removed the rubber boot at the rear of the caliper and removed the lever, spring clip and drive block/wedge that operates the handbrake part of it, but am now a bit stumped. Could someone tell me:

1. How do I get the piston out of the caliper? Is there a tool you need (or can buy) to unscrew the notched piston (I assume it unscrews), or do you drive it out with compressed air?

2. On the lever that operates the handbrake, there is what appear to be a nylon/plastic bearing pressed onto the shaft. Can this be removed, and if so, how?

I'm sure there will be more questions the deeper I get into the caliper...

[VXdeMayo]

The rear piston has a helix thread that acts as a self adjusting handbrake device. Therefore to remove the piston you should just be able to "unscrew it" using a large screwdriver. Be careful to keep the spring washers in the correct order once you remove this. The white plastic collar will just push off to facilitate cleaning.
Hope that helps.
Chas.

[mangocrazy]

The rear piston has a helix thread that acts as a self adjusting handbrake device. Therefore to remove the piston you should just be able to "unscrew it" using a large screwdriver. Be careful to keep the spring washers in the correct order once you remove this.

OK, thanks. I guess everything is just badly gummed up on these parts, as some of them have been sitting in a box for 20 years+

The white plastic collar will just push off to facilitate cleaning.
Hope that helps.
Chas.

Yours may have pushed off - mine are made of sterner stuff...    I think the whole shooting match will get soaked in diesel for a couple of weeks before battle recommences...

One last thought - do the pistons on the rear calipers wind out clockwise or anticlockwise? And does one need to push and turn at the same time, or just turn?