Flavia and Flaminia brake servo rebuild

[ColinMarr]

Here’s a post that I put on the spares required section that should also appear under ‘Flavia’:

The remote servo fitted to Flavia and Flaminia earned a poor reputation for unreliability, but in my experience a lot of this was unfounded. I successfully rebuilt the servo for my car in the mid 1980s and went on to do two more for others. The system is only marginally more complicated than the dual circuit master-cylinders fitted to Flavia and Fulvia – it you are OK with that then doing the servo should be no more problematic.

The most common fault was brake fluid getting past the seals at the vacuum chamber end of the unit, into the chamber and then into the inlet tract with lots of white smoke in the exhaust to prove it!

One of the problems then was the lack of seals. Rebuild kits were not available in the UK and at least two of the cup seals seemed to be almost unique to this system. I searched through the parts bins of a motor factor that was supposedly a Lockheed agent and I found cup seals that did the job, others were simple ‘o’ rings that were easy to obtain.

Another problem was that the design of this system involved a side-shoot from the main cylinder going off at an angle (and hence blind) to the air filter, so that it was impossible to push the piston out with a wooden dowel. The trick (leaned from the wizard Tony Amato) was to tap the flange end of the side-tube with a pin-hammer until low-and-behold the piston with its ‘o’ ring rises up out of the housing until you can grip it to pull it out. Any slight damage to the flange needs to be flattened out.

Cleaning up the bores with very fine abrasive paper, fitting new seals and putting it all back together seemed to complete the job.

Of course, you may now find an alternative remote unit off the shelf, but when I did it that wasn’t an option.

Colin

[rogerelias]

Have just found 90% of a Bonaldi servo in the garage, nearly chucked it out!!

[lancialulu]

I understand the Flavia consortium have sourced an aftermarket alternative but I would prefer to keep the originality.

Mine on my new acquisiton has been rebuilt (supposedly) recently (last 4 years) and seems to work (passed the MOT only to fail on a rear antirollbar link bush...).

Do you have any lockheed part numbers for said seals??

Also can an air line pop out the tricky piston??

Tim

[ColinMarr]

The motor factor’s parts bin that I searched though was simply a bin of hundreds of loose seals with no identification numbers. Nowadays you might be able to buy kits on the internet or through Cavalitto, neither of which was possible 25 years ago.

I looked back at my notes. The two ‘cup’ (or ‘lip’) seals were to fit into different parts of the main cylinder. One was to fit in a bore of 16.5 mm, on a piston groove 8.95 diameter X 5 mm. The other to fit a bore of 16.0, groove diameter 7.0 and also X 5 mm. I think the parts book diagram identified them as part ‘7’ and ‘11’ respectively.

I didn’t have an air-line, but I doubt if you could blow the two small pistons out of the angled side tube without somehow blocking up all the other holes, which would be difficult. If the servo you are doing is a ‘dead’ one that has dried out over time I would expect the O rings to be stuck in place and it would be impossible to tap them up.

Hope you never need to have to do it!

Colin

[Angle Grinder]

I believe the Flavia Consortium can still provide kits of seals for the slave cylinder as I recently got some, but maybe got the last kit.

My brake pedal is firm, but I do have a fluid leak that drips down from the rubber "bridging" hose that links the pipes between the back of the vacuum cylinder and the control valve pipe.

This puzzles me as it would suggest that fluid is getting past the diaphragm in either the vacuum chamber or the control valve. And yet the brakes are still effective enough to pass an MoT and to lock the wheels in an emergency stop. That said, you do need to give the pedal a fast double pump to get the sort of pedal feel that you really want. The first prod of the pedal gives adequate brake retardation if you use force, but give the pedal 2 pumps and you get the sort of pedal hardness and feel that you would expect from a modern system.

I started the car up after 6 weeks of hibernation and was definitely getting the white smoke that you refer to. I have a mechanically gifted friend with experience of overhauling Fulvia brakes so he is earmarked to do the rebuild (he has all the necessary machinery for honing the cylinder if required). I'll keep you posted on our progress.

[phil-m]

You can still have good brakes with fluid getting bast the servo you just consume fluid at a rate of knots. My brakes work absolutely fine, pass the MOT no issues but fluid loss is steadily increasing so I plan to overhaul my servo and slave cylinder in the next few weeks. 

[Angle Grinder]

But what puzzles me is the fact that the fluid seems to be dripping from a piece of pipe that should be blocked from brake fluid by the diaphragms of the Vacuum Chamber and the Control Valve. OR are you saying that fluid can leak past these diaphragms without any perceptible deterioration in the pedal feel?

[ColinMarr]

From my experience of years ago, the units that I rebuilt showed no signs of deterioration of the main seals in the vacuum chamber itself. I think the problems were that brake fluid was sucked back into the chamber (and hence down the pipe) by worn seals at the business end of the cylinder. The volume of fluid taken in this way would be tiny compared to the volume of air in and out of the main cylinder – hence no deterioration in servo effect.

The only other signs of deterioration that I saw were in the side tube off to the control valve, where grit that had got past the air filter had scored grooves, which were easily polished out.

Given a good work bench with good light and space to lay out all the bits – it should be a lovely job to do!

Colin

[fay66]

Going back to the 1970'sthis was a favourite trick on my Vauxhall VX 4/90.
the seal that the pushrod passed through had torn lips which allowed brake fluid to collect in the servo, it also had the effect of causing the engine to run faster so no amount of fiddling with the tickover adjustment screw would slow the tickover

Brian
8227

[phil-m]

So, I stripped my servo and found the vacuum chamber full (well at least 1/2 full!) of fluid, the secondary vacuume chamber was also had fluid in it. Looking at the parts it would appear that the rod from the main diaphragm had corroded where it had been sat against the slave cylinder rear seal for a length of time. It would reiterate what others have said about brake performance being absolutely fine, I guess until the leak past the seal becommes massive then the only issue is the cost of brake fluid! Rebuilding the 2 stages slave cylinders was quite satisfying, I took dozens of images showing exactly how it came apart. I have measured all the O-rings and can supply these sizes or the O-rings themselves if any one is interested. I am also going to source an alternative to the lip seals used as I think the price charged by the specialist supplier for the seal kit is slightly excessive..... I will post some images when I have down loaded them.

[Angle Grinder]

By coincidence, I just got my Flavia back yesterday from it's slave cylinder overhaul. New seal kit from Omicron ~£66, plus a new diaphragm for the vacuum chamber. Required several rebuilds as the brakes kept locking on. Lots of greasing up of the compnents and the new diaphragm eventually fixed all of this.

The pedal still has a long travel (about 50%) before it starts to firm up, but the bite and brake feel is good once the travel is taken up. Giving the pedal a second pump brings it up to where I feel it should really be biting in comparison with driving a modern car. The pedal has been like this from the start so nothing to do with the rebuild. Brakes have been bled thoroughly so I don’t think it is air in the system as it only takes one pump to get the pedal properly firm.

I thought teh extra travel might be “knock back” due to wear in the wheel bearings or warped discs pushing the pistons back, but when static and the engine off, you can pump the pedal twice to get it high and firm, wait a few seconds and the travel is again about 50% before going firm. I guess that could be air in the system, but I’ve read that stainless steel lined pistons tend to allow the pistons to glide further and more easily back into the calliper, where as pistons in unmodified calipers will stick and retract less after being released hence the pedal is higher.

Of course, it might just mean that I need to fit new pads!

[ColinMarr]

Another explanation for long pedal-travel might be that the push-rod from pedal to master cylinder might need adjusting to make it a bit longer. I found this to be quite a critical setting when I rebuilt the system on my Fulvia - I think it would be the same on Flavia. If you make the rod too long the brakes tend to bind-on when it gets hot.

Colin

[Angle Grinder]

I've had the master cylinder upgraded to one from a Sherpa van along with the correct spacer. Would a short pushrod not result in a long brake travel every time. I find that my first push has a long travel and then the brakes bite nicely, if I release once and then re-apply quickly the pedal has a nice high bite point.

Doesn't need repeated pumping and has been bled thoroughly so air in the system seems unlikely.

[phil-m]

The symptons are typical of a lack of stiffness in the system. This will be due to air or weakening hoses, it is usually a small amount of air somewhere in the system, try rebleeding with the system hot, ie after a run and see if it improves. My Sport is exactly the same, brakes perfectly acceptable on the MOT 'brake' but a second application brings the pedal up even harder. It could also be the travel between pads and discs.

[Angle Grinder]

My brake pedal travel seems to have resolved itself with a bit of use. Either that or I've modified my driving style.