Brake bleeding fulvias

[chris]

Dear Nistri - I would like to refer you to post 13 of this thread in case you missed it - I would strongly advise you NOT to completely drain your master cylinder whilst routinely replacing the brake fluid (by bleeding) as you will run the risk of introducing an air lock into the cylinder. Its true, the chances of this being a problem are reduced if bleeding with the aid of a pressurising device, but if bleeding conventionally by pumping the brake pedal, this can result in much frustration. As for corrosion in the slave cylinders, you could, of course, get these modified to accept stainless steel sleeves thereby ending the problem.  (the front cylinders (2 1/8" dia) need to be machined sparingly with much caution, as there is not much "meat" to work with).  At the same time, I machined the seats of the bleed nipples drillings to accept conventional 45 degree tapers and then used corresponding bleed nipples as used on later Jaguars etc.  Note for Neil - I  remember seeing something similiar on a lightweight alloy Dunlop equivalent cylinder, but I judged it to be an aftermarket fitment to accomodate "shorter reach" bleed nipples. Chris

[ncundy]

Chris, I would tend to agree with you on the spacers. They do not seem part of a "sensible" design as every time you unscrew the bleed nipple they run the risk of becoming unseated and moving, and of course you have no idea if they have seated properly when you re-tighten. At the moment I am not sure what to do (it is not a pressing problem as I will not be in a position to re-fit the brakes for some time), so I will have a think about possible alternatives.
Thanks
Neil

[nistri]

Hi Chris,

Regrettably I don't read this forum as much as I would like, but when I can, I enjoy it.

Well, we have different views about brake bleeding, that I guess is not a serious problem as long as the final result is the same, i.e. good and efficient brakes. In over 25 years of Fulvia servicing I never found an air lock after emptying master cylinders, maybe I was lucky as I suppose this is a possibility: the pressurized system  should however prevent this chance.

You and I have been LCM members long enough to remember a lot of debate about fitting stainless steel inserts into brake pots. Many people had written about this issue in the club mag in the past. Personally I don't like this option very much even if at times it might be the only available one. It may also depend on the car use: I live very near the Alps and, on my roads, brakes must work really hard and become very hot. It is not unheard of front pots failure because, as you correctly pointed out, there is very little metal to bore out to fit an inset.

Unfortunately I don't come often to LMC events but next time it would be good to have a chat and a pint together again. It has been a long time since the last one.

Fanalone brakes: I think the spacers are aftermarket fittings.

Andrea   

[chris]

Thanks Andrea - lovely post - I too, look forward to catching up with you in person one day.  I agree entirely with you on the stainless steel comment as regards the front cylinders anyway. On the plus side, I know of several owners who have had their front cylinders modified in this way and have clocked up high mileages without a problem, (the well-respected engineer Doug Ellis being one of them) so quality of work done could be a factor.   Note for Neil - might be worth considering the 45 degree taper mod?  I know it's non standard, but, although loathe am I to criticise original design normally, the original steel ball bearing/sphere design you could say was a bit "belt and braces" (except braces don't corrode and get stuck!)  I can remember on one occasion having to pump on the brake pedal repeatedly to free off a severely corroded-in ball bearing!  Also, sometimes when you come to strip or inspect a cylinder, you can find that the ball bearing has gone, and someone has replaced the nipple with a taper-type one - and it seems to have sealed adequately (!) Chris

[Scarpia]

Having tried everything else and revised the calipers I still was getting no pedal action and felt like I was just pumping air all the time.I even managed to track down a gunson eezibleed in holland and tried that . It bled the brakes very well one I made an adapter to fit the cylinder cap but still didn't solve the problem at the pedal.Finally I've just taken the Master cylinder off the car and found the problem.The inner piston assembly has siezed in the fully depressed position so the actuating shaft was literally pumping air as it wasn't coming into contact with the piston until the end of its travel.It goes without saying that I need to dismantle it further but in truth I presume if its so rotten as to sieze, just replacing the seals will be a short term remedy on something thats already 35 years old.I think an aftermarket replacement is the way to go but will cost a couple of hundered euros; but then what price safety?.

[ColinMarr]

Scarpia,

Your original master cylinder might not be a lost cause. I would not presume to be an expert, and not that I have ever had one seize in the down position, but I have rebuilt Flavia and Fulvia ones. If you undo the big nut and clean out the bores you are likely to find corrosion pits in the otherwise polished bores. If these are not too deep and horrid you might get away with using the finest of fine emery paper wrapped around a smooth end of wooden dowel to polish them out. Maybe I’ve been lucky, but it’s worked for me.

If you do have to resort to a modern aftermarket replacement, I would be interested to know what the options are – just in case!

Colin   

[Scarpia]

I'm sure your right Colin .I faced the same problem of corrosion with the aprilia unit but didn't want to risk this approach because of the single circuit. With the fulvia being dual circuit its less risky but the problem remains that once corrosion is set in to the surface of the bore, new seals will inevitably be prone to earlier failure.I'm guessing seals cost 30 quid a time and its a messy job .Ultimately the master cylinder is donkeys years old and a new unit brings peace of mind (at a price though). We'll see...

[lancialulu]

Corrosion is due to corrosion on the alloy due to hydroscopic nature of ordinary brake fluid. I recommend silicone which will generally prevent further corrosion.

Only problem I had was the viscosity of the silicon fluid meant I had to open up the 0.7mm feed hole to 1mm in the reservoir as surface tension (my assessment) was preventing the fluid into the secondary chamber. After that no probs at all.

All my fulvias run on the fluid which has a regal purple look in the reservoir!

Tim

[St Volumex]

Scarpia,

I've had master cylinders resleeved with stainless steel, and used new sealing washer kits with no problems - apart from getting that infamous air lock, when we replaced all our Fulvia's flexible brake hoses.  We rigged up a catheter syringe and sucked the fluid through to the rear calipers. 

I've used the (Dow Corning) silicone brake fluid Tim speaks of, but found the pedal feel wasn't as firm.   

Regards

[Scarpia]

i've also considered silicon fluid as it seems, at least on paper, to be the solution to all the ills of brake systems given its non hygroscopic properties.
In practice I couldn't find it readily here in the shops and this combined with the other doubts I had prevented me trying.I discussed the issue with my old brake specialist when revising the Aprilia brakes and he wasn't keen.It' s actually less of a concern on cars with drums than discs but there are two areas where issues can arise.The silicone lubricates (or penetrates) better than the seal manufacturers original spec takes account of and if the silicone works it way past and into braking areas such as pads you can guess the results. The other more concerning issue is the significantly lower boiling point.Unles you are absolutely meticulous , there remains a fair chance of residual "old fluid"  in the system with its water absorbing properties boiling much more readily and vapour locks leading to potential brake failure.Silicon fluid will experience its boiling condition in a brisk drive in the country where the normal fluid will only reach this on longer mountain descents.

All nice theory of course and the corrosion and water absorbtion of normal fluid are also major disadvantages of the traditional approach. But for these reasons I was advised to stick with normal fluid.Using the vehicle regularly and yearly replacement of the fluid being the least potential trouble in the long run.I suspect the boiling issue is perhaps why major car companies have not switched but knowing how companies work there is probably a financial motive somewhere. 

Not terribly keen on resleeving with stainless I'm afraid as most people secure with loctite which gradually brakes down with brake fluid (but not silicone based fluid i think)

Ultimately a well maintained system avoids most of these pit falls ....now if only I'd done that!

[lancialulu]

Re silicon this is readlily available

Demon tweak catalogue it (Automec) and it is also readily available in my local auto store so I doubt product liaility is an issue. Re boiling point, this is rated at 500def F (260deg C) and is dot 5 mil std. Dot 4 std issue is less. Admitidly racing fluid may give you 50 degrees more  but are your really steaming along that fast???

Re being meticulous - this is the first rule of messing with brakes!!! If it looks dogdy throw it in the bin.

Re brake feel - can comment as i like the feel of my brakes - assume you may have air left in the system which is the curse of Fulvia!

Best and happy motoring

Tim

[ColinMarr]

Silicone or not?

I first encountered silicone brake fluid when I rebuilt my 6th Series Aurelia B20 in about 1990. I thought it was a good idea to use it if only to avoid using the horrid corrosive standard stuff, which strips the paint off the otherwise lovely cast alloy reservoir on the bulkhead.

After investing what seemed like a lot of money for a couple of litres of it, and then losing most of it trying to get the hydraulic clutch mechanism to work properly, I gave up! I abandoned the hydraulic clutch (what a disaster!) in favour of an improvised simple mechanical linkage. I abandoned the silicone brake fluid in favour of DOT 4 mostly because wise people of the time said that the seals of that period were made of a rubber/ plastic composite that absorbed the standard brake fluid which allowed them to expand and help secure the necessary seal. The fear was that silicone fluid would not work in this way. DOT 4 worked well on the B20 and now on the Fulvia and I have not been tempted since to go back to silicone.

Colin

[Scarpia]

Lancialulu,

when I said not readily available here ; "here" means Belgium which perhaps was not clear.

As you can imagine I only proceed at speeds "forseen by our legal framework" but unfortunately brakes get a lot hotter than people realise.A normal town drive can already push the temp. up to the 100 degrees mark.Lengthy descents or racing can easily climb into the 400 + zone hence the glowing discs/calipers that can result.So its at least feasible that water retained in any residual old fluid would be heated much more quickly if basically surrounded by silicone fluid with a much lower boiling point.

It's probably academic .As you say being meticulous is everything and if the system is properly cleaned out then it wouldn't be a problem.

[St Volumex]

I agree with Colin re DOT 4.

I've tried silicone in my Beta too with the same spongy results.

When I went back to 'normal' brake fluid all sponginess disappeared. 

[lancialulu]

silicone or not....

Every one to their own. My HF ran round  various tracks incl goodwood (will there be one in 2008??) with no adverse pedal problems. I like the fit and forget idea - my 1300 has had silicone in since 18 years ago with no seeming problem to seals.

It is more viscous so needs a different approach and yes I spent 2 days once pumping air until I let gravity do its job. Cant say I have ever had a spongy feel to the pedal but they have never been rock hard like my MX5 (oops) which has dot4.....

Tim