Lancia Motor Club

Hi
Am looking for some experience or advice on my brakes - have a S3 1976 , have had it for about  9 months , and for the first 8 months all great , however recently it has developed a serious braking issue - After approx 10 miles my brakes will begin to engage independently , initially slowing me down , however after a minute or so bringing me to a full standstill - brakes fully locked on - all without me touching the brakes . The pedal is rock solid …  After 20 / 30 mins by the side of the road the hard pedal will disappear and brakes unlock… This has developed over the last few weeks thoughts are focused on the servo / master  as it’s all 4 wheels that are locking up - Has anyone experienced similar , or has any experience - advise would be much appreciated as it’s practically undriveable currently .
Cheers

The rod in the servo is slightly too long.  You need to take off the master cylinder from the body of the servo and reduce the length of the actuating rod by screwing the ajustment in a bit.   This is a well known feature of Fulvias.   In an emergency you will find that loosening the pipe nuts at the master cylinder will release a bit of fluid and relax the brakes.
I think there is a thread on this here https://www.lancia.myzen.co.uk/forum/index.php?topic=6195.msg43544#msg43544

Will certainly follow up on that , can see how the rod being too long could inhibit the master cylinder from returning to a fully released position , however am still confused by the brakes applying themselves and the progressive increase in force  of application. Am thinking vacuum supply or lack of - could that induce the servo to engage  ?     Quick visual of hose - correct type - vacuum not fuel , will examine / replace the valve  Shall let you know what I find with the rod length .
Thanks

Fluid expands when heated up..... so when issue starts it creates what is called positive feed back and makes matters worse...

Also check the brake pedal under the dash is not sticking too, hot weather can cause them to bind.

Had a similar issue with a Fiat 124 Spider. Easily diagnosed as the push rod length by slackening off the two locknuts half a turn. If that resolves the problem then shorten the rod by the thickness of half a turn on the locknut. Repeat until the problem goes - so long as you still have brakes!

I haven't had them bind in hot weather but I've had a solid brake pedal, which I only discovered once I'd set off, most disconcerting.

Presumably the fact the fluid expands in hot weather was to blame as the car had been sat at a show in blazing sunshine for several hours.

I was able to get home using engine braking and gentle application on the pedal itself but it was not a fun journey.

Its been a couple of years since I worked on Fulvia brakes but I have certainly experienced solid and soft pedals over the last 50 years on several occasions.
Either issue is very disconcerting inevitably  leading to a loss of confidence which is not pleasant.
I have to say that adjusting the length of the rod when a solid pedal has occurred ( assuming previously the brakes were fine for some months) has never worked for me.
On almost every occasion the problem has been with the master cylinder ( and once with the remote servo on a GTE Berlina). I cant tell you exactly why each problem occurred but my fail safe solution was always to fit a new master cylinder (or very occasionally re-seal the m/cyl if a new one wasn't available).
As to the suggestion that problems might be caused by fluid expansion, how is one then able to push the pistons back in the wheel cylinders when fitting new pads?
To me, its a bit like the false economy of using old tyres - the integrity of your braking system is vital for road safety - and not just for you of course.
Chris

Shortening the rod has certainly worked for me though.    Certainly the thing to try first.    Not always due to hot weather either, just using the brakes is enough to set it off.

And if you don’t mind working blind upside down in the footwell you can adjust the length of the pushrod without disturbing the servo. What fun!

A busy day today -  On the brakes - changed the servo non return valve , bleed the brakes , reduced the fluid level in the reservoir as it was above the max . Additionally on the engine changed the leaking carb mounting , and whilst that was off changed the gasket on the leaking fuel pump , which had been leaving an oil slick on the garage floor . Did  need and have help - Thanks Tim ,  his experience particularly when it came to balancing the carbs after removal was vital. The test drive with the balanced carb was much more responsive , and although only 1/2hr and 10 miles no repeat of the phantom braking ...... could it have been as simple as overfilled reservoir  or a  sticking non return valve . Time will tell ,a longer drive is planned for this weekend.
Oh did contort myself into the drivers footwell to checkout the rod, now I am a bit more familiar and I'll be ready for this potential adjustment  should the issue arise again....At the moment am still far from confident   

The rod you need to adjust if at all is between the servo and m/c not in the pedal box.

Perhaps it's different on late series cars, but with S1 Fulvias you can disconnect the pushrod from the ball on the brake pedal, loosen the lock nut and adjust the length of the rod.

Do these two adjustments have two different functions? Is the more accessible one for pedal free play?

 Richard

Well - that's all the easy checks exhausted  - and guess what 6 miles and the brakes applied - rock solid - waited 1/2 hr for them to release and drove back home - Time for the master cylinder to come off to expose the servo push rod, which appears to be the favoured cause  . First time taking off the cylinder, looks pretty straightforward, if perhaps potentially a little messy.
May get the cylinder tested whilst it's off, and will be looking for that rod  not to be flush as I'm looking a clear culprit. Am away for a few days so perhaps will get to it next week.

With high underbonnet temp, internal components of the master cylinder might distort and block the normal operation. Moreover, it is not rare to find out that the internals had been refitted incorrectly.

On a S2 car no.15 on the diagram is the critical item to adjust correctly, there is no pedal box adjustment of the rod in side the car as Tim pointed out.

Master cylinder off this afternoon, was hoping to find the servo pushrod protruding beyond the casing - Unfortunately not - it's absolutely level - touching my straight edge.
Was wondering if there was value to winding it back a couple of mm with the case ?  has that approach worked for anyone or is level with the case absolutely the right set up.
Although no apparent leaks from the MC  rear seal am beginning now to think of sending the MC off to Omicron to  be tested.
The struggle continues

Whilst things are pointing to this being a master cylinder issues let me just introduce a possibility that I suffered quite some years back ... that of brake line internals collapsing.

Whilst all outward signs were that the brake lines were fine the constriction caused by collapsed internals was the root cause of a sticking brakes issue.

In your situation I'm reading that brakes are fine but after not very long they stick on; wait for a while and everything is okay. Could a situation exist where hydraulic pressure is enough to apply brakes but collapsed internals prevent fluid release back from the on situation (at least until you've waited long enough for fluid to seeps back)? Realising this is unlikely if all brakes stick on but that's worth questioning / double checking if the MC angle is seemingly drawing a blank.

if you adjust only one turn will be enough

Just tried and one turn seems to equate to just over 1mm , and also seems despite there being more thread visible the max I can screw back in .... so I'll reassemble , bleed and give it a go - Fingers crossed - Thanks

when  the brakes stick on is it all 4 or just the fronts or just one??

All 4 wheels lock up.

There was mention at the Yorkshire Meet Up yesterday of a non-return valve in the vacuum pipe that feeds the servo from the manifold? This can apparently seize and cause binding. One of our Fulvia members also has this issue......

Easy enough to remove to check and if necessary replace.

Thinking about the problem, the only thing that's outside your control that's a variable capable of affecting the 4 callipers when the car's being driven is the brake servo valve. There's not much to go wrong with it because it's so simple, but after a few decades who knows.

Tentative positive news - Servo pushrod wound in a turn , reassembled , bleed , which went quite smoothly, took it out for  a run , the trip to Liskeard and back , which on the last two occasions we failed to make it without needing 1/2hr stop  to allow the brakes to unseize - well it was positively uneventful no phantom braking. Looking forward to pushing out on a longer run at the weekend and lets see. Appreciated  the input and advise... Fingers still crossed