News from the soggy pedal front

[Michael Tryton]

2nd photo of the reluctant piston:

[lancialulu]

Not sure if this is relevant? My Flavia this year developed something similar in that the brake pedal would go down c1/3 before activating the rod (then the brake would work with a firm pedal). I deduced that the rear piston had got stuck for some reason someway down the bore. Now on the Flavia the is a rear and front priming pump in the reservoir. Out of curiosity more than any thing I gave the rear plunger a push and it went somewhat then after it had returned it would not push down anymore (ie the MC had fully primed). Now I had a firm pedal right at the top where I remember it had been normally. After several weeks of use it has stayed in the normal position. Odd....

[ColinMarr]

I think you have identified the problem! As you say, the piston is not fully retracting, either because it is jammed or the return spring(s) have failed – hence no pumping action. Sorry, but I guess you have to dismantle it and start again. If there are any deficiencies in the m/c body itself, I happen to have a good re-usable one.

[lancialulu]

As Colin says this is the problem. It may be a hydraulic lock in the incorrect assembly of the one way valve at the front of plunger 2 (see attached).

BTW not all seal kits come with 4 u seals. Most come with 3 u's and an o ring. I cannot remember if the o ring replaces the rear seal or more likely the middle seal... Maybe someone can remember?

[Michael Tryton]

Well, I've taken M/C off again and found that, yes, even after draining the unit, the 1st piston after the servo is absolutely stuck; so am giving up and sending it off to Past Parts, who are familiar with this type. Let's see what they make of it.

What I'm calling the 2nd piston is the one at front of the car and furthermost from the servo and that was still fine, completely free; as of course they both were initially, after my rebuild & reinstallation.

Thanks for the attached pdf - that's the same diagram from the workshop manual which I was working to when fitting the new seals to each piston, although poor print quality makes orientation of some seals passing ambiguous.... This and the choice of which seals to use from the kit has been discussed on here before - the rearmost one on the 2nd piston can either be a 'top hat' shape like all the others, or replaced with an 'o' ring, which is what I did. The 1st piston, which is stuck, was all 'top hat'.

[Michael Tryton]

My master cylinder came back pretty promptly from PastParts, with its piston unseized and their invoice duly endorsed:

"M/CYL SLEEVED 80.00. LANCIA MASTER CYLINDER REBUILT USING SLEEVE KIT SUPPLIED BY CUSTOMER. THIS UNIT CANNOT BE SLEEVED AS IT IS NOT A STANDARD BORE SIZE. WE HAVE HONED THE BORE WHICH IS NOT IN THE BEST CONDITION AS BEST WE CAN".

They also did me the courtesy of phoning me just before sending it back. Confirming that they had done this type of Lancia master cylinder before, but they held no dedicated sleeves in the right size (is it 28mm for a 21mm cylinder like this?) to mirror the curious interrupted passageway which you can see inside this master cylinder, which presumably requires three sleeves in a row.

The cost as billed to me was £80 plus £8.75 Fedex delivery; plus 20% VAT; making a total price of £106.50.

I refitted the cylinder on the afternoon of receipt and, after another quick bleed all round the following day once the fluids had settled, I drove off - job done! While the lorry that suddenly stopped dead in front of me necessitating an emergency stop gave proof that things were indeed now right.

Perfection is rare in this life however, and after successfully being assembled, disassembled, then reassembled over and over in the course of this labour, the lingering fly in my ointment now is the rearmost supply pipe to the master cylinder which now constantly seeps fluid. (See picture). I've taken it off again, added a new copper washer/then another copper washer, gradually made it tighter AND TIGHTER, but still it leaks....

Having repeatedly tried but failed, I've run out of fresh ideas (plumber's tape?) and throw this latest niggle over to the Panel. Suggestions?

[lancialulu]

try to anneal the copper washers. Heat up to cherry red and let cool down. Works for me.

[rogerelias]

not sure if it's my eyes.But looking at the picture is there a copper washer missing between the cylinder and the union, can see on the front one but not on rear one, but it could be my eyes 

[ColinMarr]

I find it curious that they expected to sleeve it, but couldn’t and then simply honed the bores. I hope that is adequate treatment. Do you know how badly pitted the bores were in the first place?

[chriswgawne]

My experience of OE (Sabif?) Fulvia S1 and S2 and Aurelia aluminium master brake cylinders is that to work properly, the bore needs to be very highly polished with honing not being smooth enough. And I assume they used aluminium because a steel one couldn't be polished highly enough?

Discussing this with Omicron a few years ago,  if one gives one to Omicron to refurbish (which I have actually never done) , they regard the highly polished inner bore as being critical. They also have the facility to bench test under pressure.
I understand this need for the highly polished finish is to ensure the seal carrier ( Aurelias have one, Fulvias have two as dual circuit)  returns correctly to rest so not only do you get a firm pedal but also in the case of Fulvias the inner seal carrier returns to the correct position using the different rated springs either side of it.
In both cases, if this doesn't happen, one gets ever reducing pedal travel with the brakes ( front in the case of Fulvia I recall) locking on in the end.

Just recently, I tried a visually perfect Fulvia master brake cylinder which I have fitted twice with new seals and each time the brakes have locked on in the end.
Chris

[Scott]

I can see from this topic that my related topic of a couple of years ago (http://www.lancia.myzen.co.uk/forum/index.php?topic=9756.0) has already been spotted/cited.

I can confirm in this instance that after problems with my own master cylinder I sent a replacement (kindly located for me by this forum) to PastParts for checking and restoration. Having had a chat with them at this time they confirmed they would need to hone and sleeve and indeed I have just gone and dug out the invoice I received and it specifically says "...sleeved and assembled by us with new seal kit.
This does seem to be at odds with the wording on your invoice Michael so I'm not sure what's going on.  [I note that you supplied a 'sleeve kit' with the item - did you get this back?!].

Whatever PastParts did to mine seems to have worked well as, for anyone who read a short article I wrote in August 2018's Viva Lancia!, I then did a 3,390 mile trip around Europe including lots of braking action coming down various Swiss mountain passes!

As to your leaking; I've taken a close up of my connections for comparison. As well as Roger's observation could an alternative be that your new washers are actually slightly too thick? Could this be preventing the connector seating properly?

[ColinMarr]

I had hoped this thread would have continued a bit longer, if only to resolve the differences between sleeved, honed and polished bores. Has anyone had real experience of having a Fulvia master-cylinder re-sleeved successfully with a steel tube liner? And if so, what was the interior finish of the steel bores?

Colin

[Michael Tryton]

I'll certainly be updating this thread shortly, once my other commitments allow me more time.

Had also noticed some ambiguities in parts-terminology seem to have crept in, which won't help the narrative, so will happily respond to those from my point of view - once I get time to sort that lingering leak around the brake pipe unions, and report back to The Panel.

(Hold The Front Page!)

[chriswgawne]

Like Colin, I am interested to understand exactly what is and isn't possible as rhd OE Fulvia S1 brake master cylinders aren't available. I know alternative master cylinders can be fitted but if possible I want to stay with the original part and appearance.
Chris

[Jaydub]

Just a thought Michael, are the faces on the 2 way block absolutely flat/parallel and the inside diameter of the washers a snug fit on the banjo bolt, as that could be the source of the leak? If the bolt has been over tightened and the block faces have dished inwards (concaved) the washers may not seal.