News from the soggy pedal front

[Brian Long]

This all sounds very much like the problems that I had with my Flavia 2000 coupe's brakes. Over a period of time I finished up buying both a new booster and a new 'old-stock' (NOS) master cylinder in an effort to get a reasonably firm pedal. All to no avail, after a few applications the pedal would go to the floor.
It transpired that the master cylinder has an anodised bore. If not kept 'wet' in storage it will develop microscopic oxide blemishes which will destroy the rubber cups.
In my case there were incredibly fine score marks on the cups but enough to let fluid by and the pedal to sink to the floor.
The cure? Have the master cylinder resleeved in stainless steel. Several years later the brakes are still as good as ever although not rock-hard which I understand is typical of the Dunlop system.
P.s. Want to buy the shares that I have in a brake fluid manufacturing company?😊😊😊

[lancialulu]

Colin’s point is a good one......

Re Dunlop braked cars being softish this is not my experience. My oem servoed system on my Flavia Vignale is rock solid pedal at the top as is my unservoed Fulvia 1.3 HF. Its all about getting the air out imho.

[fay66]

Colin’s point is a good one......

Re Dunlop braked cars being softish this is not my experience. My oem servoed system on my Flavia Vignale is rock solid pedal at the top as is my unservoed Fulvia 1.3 HF. Its all about getting the air out imho.

No soggy pedal in my 2c either with no servo.
Brian
8227   :

[lancianut666]

All sounds familiar to me I used a 5 litre container on my Flavia Coupe brakes... mind the hydraulic pressure jacked out the stainless steel liners in the wheel cylinders not helpful...the Appia ones are just as fiddly but practice makes perfect...
Clarkey

[Michael Tryton]

Well I've now had chance to act on Tim's latter suggestion to me, by disconnecting & blanking-off the manifold pipe.

I'd say the pedal DOES feel a bit harder, but it's still still rubbish. Although - as before & always - I've retained some vestigial braking effect through the front which, in combination with the handbrake, is enough to stop her rolling at low speeds.

Something else I think I can also feel is a sensation of each seal overcoming resistance as it is forced down the shaft - or is that just my paranoid imagining?

And I've also gained something else new: a hiss of air when I press the pedal down. A sinister development which (although I can't remember why exactly...) I do know, from reading on here, is one that should distress me even more - provides something else BAD to fret about? (Possibly involving a new life, to be spent in the front footwell?)

P.S. Yes, I did inspect the bore carefully and, yes, it did look OK but, hey, "microscopic scoring..."? Well, who can say? At least it's helpful to know that buying a new M/C is apparently a waste of time (and money too)......  

[fay66]

Colin’s point is a good one......

Re Dunlop braked cars being softish this is not my experience. My oem servoed system on my Flavia Vignale is rock solid pedal at the top as is my unservoed Fulvia 1.3 HF. Its all about getting the air out imho.

No soggy pedal in my 2c either with no servo.
Brian
8227   :

[chriswgawne]

We have 2 S1 Fulvia Sedans with OE Dunlop brakes.
The GT brake pedal is solid with relatively short travel whilst the GTE with a remote servo has a longer pedal travel but still with a solid feel. The GTE has a front/ rear brake balancing valve with a nipple and this valve ( only fitted to GTEs) is tucked up above the central rear of the subframe. It's a devil to get all the air out and i have never understood why the remote servo doesn't have a bleed nipple on it.
Chris

[Michael Tryton]

Well my 1.3 coupe is - as all Series 2 are - equipped with a Girling system.

So am I to understand the panel's suggested solution to its current problem is retro-converting her system to a Dunlop one?

[Brian Long]

Regarding the hiss of air when depressing the pedal. That too was one of the problems that I encountered with the Flavia's brakes. Turned out to be a split diaphragm in the booster due to the car' s long period (17years) of being laid up.
In normal operation, the booster does exhaust a small amount of air into the cabin, there is a sponge rubber dust filter in there, but should be inaudible to all but the most acute of hearing.
To establish whether the booster is functioning as it should, after running the engine, turn off the ignition and pump the pedal. The pedal should move progressively higher over two or three strokes and also feel firmer. Leaving your foot lightly on the pedal and starting the car should result in the pedal 'sagging' sliightly.

[ColinMarr]

I don’t think the soggy pedal has anything to do with the servo. Girling brakes are good and there is no point in considering converting to Dunlop. Don’t give up!

[Michael Tryton]

Acting on Brian Long's advice, I reconnected the manifold pipe (also replacing a length of it prior to the inline valve, for good measure) and ran the engine to carry out the 'booster' test he describes above.
Then I pumped the pedal as Brian suggests. This established that the booster/servo element is working - it behaved as he said, though not so much in that 'pedal-sagging-when-you-rest-your-foot-on-it' bit.
With all that established, let's recap on the history of this incorrigible but characteristic Fulvia fault:
M/C professionally rebuilt by a garage, with a new seal set fitted about 5 years ago and, although described by them as "difficult to bleed", it has been fine until about a year ago, probably caused by a period of storage with little (not no) use.
M/C rebuilt again by me now, and I have to say the 'old' seals looked perfect with no marks or striations, which begs the question why they were no longer up to the job?
The bore of M/C had looked fine to me too, squinting down it, and I used a very small quantity of brake grease on reinserting pistons & seals so as not to scratch the precious cylinder-lining as they went in, as suggested in one of the posts/threads on here.
The car's whole system has then been bled to the point no air bubbles appear at any of the calipers.
Bleeding the M/C on a bench was a non-starter for me, as unable to do this without brake fluid spraying everywhere or any certainty it would stay airtight in the process anyway. However, thinking about where else could be left for air to lurk, the only place I can think of is the far end of the master cylinder, at that end-cavity sealed off by a very tight 32mm nut. Could an air pocket survive in there and cause these symptoms?
And wherever any surviving airlock might be, could a professional power-bleeding apparatus make any difference? (I've no access to a compressor).
Over to the Panel!

[lancialulu]

I think you may still be needing the reduce the pedal rod be c1mm. With the reservoir off you can examine carefully the feed holes. I actually opened one up (the rear one - without the pistons/seal in the body) with 1mm drill (as I was using silicone fluid and felt there was too much viscosity for the fluid to flow easily). In retrospect I think this was a wrong diagnosis and what I had done was effectively reduced the pedal rod. Anyway after that tweak the pedal returned immediately to the correct feel.

I still also think you need to bleed by the pedal and not pressure alone.....

[Michael Tryton]

Which is consistent with Colin Marr's grim observation:

"Although you measured the distance between the projecting rear end of the m/c and the servo it may be that the length of the push-rod between the pedal and the servo is not allowing the m/c piston to retract beyond the fluid feed hole, so that it doesn’t pump. It is a pain in the neck to do it (literally!) but you could try adjusting the length of the push rod by shortening it a few turns, which should allow the piston to come back a mm or two."

However, being protective of my upper spine, I wonder if maybe it's not the actual length of the pushrod that's wrong, just the M/C piston being sluggish in returning? Not as a product of any excess length of pushrod opposing it, but via some mechanical resistance in the bore? (It did feel a little like that even off the car, post rebuild, but I guessed that was probably just the new seals, keeping it tight by dragging a bit).

Anyway, lacking the appetite for 'Trial by Footwell' or intractable new obstacles bound to arise during its tortuous processes; let alone to incur so much pain while still achieving precisely nothing; I will instead call-on my glamorous assistant and go with Tim's less arduous bleeding-by-pedal suggestion.

So thanks for the continuing advice, gents, and I undertake to report back in due course:

[lancialulu]

Also Michael

A quick dodge for pedal adjustment is to slacken off the master cylinder from the servo and pack say a few penny washers in the gap and see if that makes any difference....

Tim

[Michael Tryton]

I did like Tim's bit of lateral thinking about achieving change in the push-rod length by adding some 'penny' washers, instead of grovelling in the footwell; so disconnected my M/C from the booster-cum-servo again so that I could insert some; prior to excecuting that traditional two-person bleeding exercise which he'd also recommended.

What this preamble revealed is how the M/C brass piston doesn't seem to move outwards from the M/C housing like you think it might, once released from the pushrod. It has stayed short and immobile - as photos.

Is this how it should behave? Because if it is dragging and loath to expel itself from the M/C housing, could this be the root of the problem?

Over to the Panel again!