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Author Topic: Brake bleeding problems - possibly Master Cylinder  (Read 1253 times)
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davidwheeler
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Posts: 1238



« Reply #15 on: 26 June, 2021, 10:31:39 AM »

There is, incidentally, a diagram of the master cylinder in the technical information thread.
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
nthomas1
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Posts: 769



« Reply #16 on: 26 June, 2021, 04:03:31 PM »


Thank you David, Chris and Tim for your input.  I've now removed the front calipers and they are with Classicar Automotive for refurbishment.  I've started the process of removing the master cylinder and will attempt to refurbish that myself with a repair kit.  It will be interesting to see what condition the cylinder bore is in.

The cross section digram of the master cylinder in the Technical Section will come in very handy.

It's interesting how you go down some blind alleys when working on a car.  The brake circuit diagram in the S2 owner's manual incorrectly shows the large front brake pistons at the bottom of the calipers, whereas the TAV and physical inspection confirm that they are in fact at the top of the calipers! 





* IMG_5193 copy.jpg (779.36 KB, 1276x1209 - viewed 31 times.)
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Norm Thomas
Ormskirk, Lancashire

Own:
1973 Fulvia S2 Coupe
Previous Lancias: S2 Coupe and S3 Coupe in late 1970s
nthomas1
Rebel Poster
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Posts: 769



« Reply #17 on: 11 August, 2021, 04:43:17 PM »

I’ve now refurbished the master cylinder.  The objective was to see if it was a master cylinder problem that was causing me to get no fluid pressure at the front top caliper pistons.   Getting the front 32mm nut undone was the first challenge.  I tried with it still in the car, using a two foot breaker bar on the 32mm socket.  Wouldn’t budge.  Removed the master cylinder assembly from the car and held it in a vice.  Still no joy with the breaker bar.  A friend recommended trying an impact wrench - so I tried, somewhat sceptically, with my relatively low powered impact screwdriver and the shock waves did the job.

Note that the spring behind the nut is quite strong, and will likely shoot out.  It’s a good idea to label the spring, and to keep all components in order and with the correct orientation as they are removed, to assist in reassembly.  And note that the first spring that comes out is shorter than the second one.

I removed the front plunger, by first removing the limiter screw in the bottom of the front fluid chamber, and then pulling  the plunger out using a pair of long-nose pliers.  I removed the small circlip and pulled the various components off the plunger .  The two portions of the plunger can be separated by clamping one end in a soft-grip vice and levering the other portion off gently with a pair of screwdrivers.  

Then I removed the larger second plunger, by unscrewing the limiter screw from the bottom of the rear fluid chamber.  The plunger assembly was then withdrawn through the front, the same way as the first plunger had been removed.   It needed a gentle push from the rear with a wooden dowel, being careful not to scratch the bore.

I cleaned everything and inspected and cleared the holes that fluid passes through.  The component parts are shown in the breakdown picture below, with TAV reference numbers against each part.  I inspected the cylinder bore by sight and touch.  Mine was in exceptionally good condition, with no marks or corrosion detected.  Note that there is  a small o-ring just inside the rear of the cylinder body that should be removed/replaced and the groove that it sits in should be cleaned.  I cleaned the outside of the body with a small brass wire brush on my Dremel.

I had bought a repair kit, so next step was to identify where the seals and o-rings in the repair kit should be positioned.  Most were obvious, but I ended up with one seal left over. It was a seal identical to the one fitted to the rear plunger at TAV item 11.  Scratched my head for a while, and only when seeing a photograph of a front plunger for another Series 2 did I understand. Apparently, there are two designs of front plunger, and they are interchangeable.  They are shown side by side in one of the pictures below. The one in my car has a narrow groove that takes an o-ring at TAV item 38.  The flanges either side of the groove are of equal thickness.   The right hand picture shows the other design, with a wider groove that takes the same seal as used in the rear plunger.  The flanges in this version are of unequal width.  ***Beware** because the right hand design picture (which somebody sent me) shows the seal facing the wrong direction.

The repair kits from at least three suppliers contain both the o-ring and the seal, so anybody with a plunger like mine will end up with a spare seal left over.  Anybody with the other version will end up with an o-ring left over!  Of course there’s nothing with the kit to tell you this, and I’ve not seen it referenced in any of the manuals or forum threads on this subject!  

The TAV diagram seems to show my plunger design.  The TAV illustration is somewhat misleading as It does not show clearly that items 38 and 11 fit over the plungers, (rather than being positioned behind them), and somewhat confusingly labels item 38  as “connector”.

Fortunately the repair kit included a reservoir cap - useful as mine had become brittle and was dropping bits of rubber into the reservoir mesh filter.

On reassembly it is important to point the lips on the seals in the right direction, as I have illustrated in the disassembly picture.  I fitted new circlips to each of the plunger assemblies.  The assemblies are fed back in the same way they came out, using some brake fluid as a lubricant.  After each plunger is installed its limiter screw should be refitted in the base of the fluid bowl.  It’s worth holding the plunger alongside the cylinder body before fitting in order to see where the recess should be approximately positioned before the limiter screw is fitted.

I bench-tested the assembly by filling it with brake fluid and pressing the plunger repeatedly to check that fluid was being expelled through both front and rear brake line openings.  All seemed to be working correctly.



* A - Removing 32mm nut.png (754.03 KB, 1020x406 - viewed 22 times.)

* B - Limiter screw and first spring.png (560.41 KB, 1134x293 - viewed 27 times.)

* C - Plungers.png (516.64 KB, 1134x237 - viewed 21 times.)

* D - Parts and TAV xref.jpg (499.63 KB, 1843x828 - viewed 22 times.)

* E - Different front plunger designs.png (601.27 KB, 1077x378 - viewed 17 times.)

* F - Ready to fit.JPG (527.55 KB, 1984x1073 - viewed 16 times.)
« Last Edit: 11 August, 2021, 05:00:12 PM by nthomas1 » Logged

Norm Thomas
Ormskirk, Lancashire

Own:
1973 Fulvia S2 Coupe
Previous Lancias: S2 Coupe and S3 Coupe in late 1970s
nthomas1
Rebel Poster
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Posts: 769



« Reply #18 on: 12 August, 2021, 08:48:00 PM »

I have fitted the overhauled master cylinder (m/c) to the car, first checking that the nut on the front of the spindle projecting through the servo was flush with the front surface of the servo.  I replaced the large o-ring around the rear projection on the m/c body, that came with the m/c repair kit.

The front calipers came back shining brightly from Classicar Automotive.  Their charges were not that much more than an overhaul kit would have cost me, and the quality of their work seems to be excellent.  It seems like caliper refurbishment is popular at the moment judging by the boxes and boxes of calipers in Classicar’s small reception area, with yet more boxes arriving by courier as I waited to collect mine.  They quoted me two weeks to do mine but took four, and are now quoting six to eight weeks.

I fitted the calipers, using new split pins, anti-squeal shims (were missing) and new flexible brake pipes.  The brackets that hold the flexible pipes at their lower end are marked “A” and “M”, the A standing for Anteriore (front) circuit for the large top pistons in the front calipers,  and the M for Mixed circuit which controls the rear pistons and front lower pistons.    I then reconnected all five brake lines to the master cylinder, and tracked the two “A” front ones to make sure I had them connected to the correct (top) pistons on the front calipers.  Note that the Owner’s Handbook for the S2  incorrectly shows the large pistons at the bottom of the front calipers rather than at the top!  The three brake lines from the rear port on the master cylinder feed the Mixed circuit (rear and front lower).

I then bled the system, using the old fashioned gravity method with my wife pressing the brake pedal as I shouted “press” and then “release”.  I used a rubber tube into an overflow bottle - keeping the top of the tube above the level of the nipple.   I bled the left rear and then the right rear, then the left front lower and right front lower.  That took care of the Mixed circuit serving all 8 small caliper pistons.  I then bled the “A” circuit - front left upper followed by the front right upper.  As the system had been pretty much emptied of fluid before I started  I then repeated the entire bleeding process starting again at the rear to make sure all air was out of the system.   I probably used twice as much brake fluid as I needed to but wanted to be sure I’d thoroughly flushed out the old fluid as well as the air!

When the rears were being bled I had the car jacked up using the central axle jacking point to ensure that the balance limiter valve did not restrict fluid flow to the rear calipers.

I’m pleased to say that the problem I encountered a few weeks back - no fluid pressure at the front top pistons - did not repeat itself.  So the master cylinder overhaul seems to have cured the problem.  Although I found nothing untoward while overhauling, I suspect that condition of one or more of the old seals or o-rings may have been the cause of the problem.


* a - Master Cyl reinstalled.png (812.51 KB, 1134x394 - viewed 18 times.)

* b - Refurbished fronts.png (941.88 KB, 1304x373 - viewed 18 times.)

* c - Caliper Install.JPG (773.89 KB, 1276x1488 - viewed 20 times.)
« Last Edit: 13 August, 2021, 07:28:11 AM by nthomas1 » Logged

Norm Thomas
Ormskirk, Lancashire

Own:
1973 Fulvia S2 Coupe
Previous Lancias: S2 Coupe and S3 Coupe in late 1970s
davidwheeler
Permanent resident
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Posts: 1238



« Reply #19 on: 13 August, 2021, 08:45:25 PM »

A very useful posting.  Thank you very much for this.
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
drdafeller
Member
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Posts: 22


« Reply #20 on: 18 August, 2021, 08:20:22 AM »

I wanted to thank the OP for starting this thread, both informative and timely! I have engaged in the same process with my 71 Fulvia and while I am getting to the end of the process, I have to say that Norman's 'all I had to do was bleed it twice' would have been a most welcome episode in my garage. I rebuilt the master cylinder, installed braided lines and all new hard pipes front and rear, and had the excellent service at Bigg Red rebuild all four calipers. This all went back on the car like a piece of cake. And then the horror started.

I began with the pressurised method for the bleed and got a bit of traction. Then I went to a sucking system with a pump on the bleed nipple at each caliper. This got flow going to all pipes, Then I went with the traditional wife on the pedal method, and got a wee bit of pedal feel, but then perhaps let the MC level get too low and pumped air back INTO the system, so started from scratch with the Gunson. This morning I could get pedal feel after a few pumps and then went back to the Gunson which seems to finally be doing the trick. I don't know how many times I've walked around the car from caliper to caliper, but it seems to be paying off.
 
I also have to admire Norman's use of only twice as much brake fluid as required. I'm sure I've spilled the overflow jar enough to fill and bleed two or three Fulvias at this point!
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