19mm bore master cylinder in favour of Sierra 22mm

[wowblaauw]

Hi All, I'm having a bit of a mare; I decided during my nut and bolt rebuild to replace the Sierra 22mm master cylinder with a Fiat 128 19mm bore master cylinder to get get a better peddle. While I managed to use 10 x 1 to 10 x 1.25 adaptors for the existing brake lines I decided to use remote reservoirs which in turn has caused issues. I am using GBS ATR remote reservoir adaptors to run braided lines to the remote reservoirs - this is my issue. Regardless of what I am doing either one or the other or both leak fluid during priming and bleeding. I just can't get them to seal.

Anyone done this or help in getting this to seal would be great.

As usual, thank you in advance

Craig

[Sparepart]

No I have never done this. However if you look at this adapter as part of the ATR remote reservoir kit you will see that it uses a fibre washer as a liquid seal. I attach an image that I scraped from their catalogue. In your picture above I can see you have a washer but it's not clear if its fibre. Oh! just thought it might be copper not fibre.

Edited September 13, 2024 by Sparepart
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[wowblaauw]

Thanks for your response. The leak is at the master cylinder to adaptor and not adaptor to fitting. I’ve just realised that the mc reservoir inputs are marginally larger in the fiat mc than the sierra. I just wondered if others on here had done the same side grade and how or what they did when fitting remote reservoirs.

[wowblaauw]

For any one else looking to do this upgrade, the Sierra MC reservoir output diameter is .34mm larger than that of the Fiat which is why I am leaking. I have ordered a set of plastic (horrible I know) adaptors with barbs which will push fit my hose and then to AN4 adaptor and hose to Reservoirs,  Also the Fiat fittings are 10 x 1.25 whereas the Ford are 10 x 1.0 making it difficult but no impossible  - I found a hydraulics company in Rotherham who supplied me with the adaptors which worked well.

I have since realised that the Fiesta MC has the same outputs as the Sierra and almost the same mounting and also has the 19mm bore - should be an almost straight swap.

Cheers

Craig

[Peter Bell]

KA master cylinders have been used too.

[wowblaauw]

Ok, the Fiat 124/128 19mm master cylinder is 0.3mm smaller reservoir diameter than the sierra - hmmm, ideas?

going to chat with mo at the show

[wowblaauw]

Just thought I'd share the final working machinations of changing to a fiat master cylinder from the trusty Old Ford unit - what a palaver! and thats just being polite...

Having made an adaptor out of some old 10mm aluminium plate I had lying around to join the fiat master cylinder to the Sierra style fitting on the Zero chassis, it was then on to the job of joining up the existing brake lines.

Rather than replace all of the brake lines, I found a company in Rotherham that made appropriate adaptors to change the 10 x 1.25 to 10 x 1 connectors and made joining pipes as the rear pipe was further away being a slightly longer MC. I then had to contact GBS in order to make me appropriate adaptors for the remote hoses to reservoirs. 

GBS very kindly made the appropriate (for a fee of course...) changes to my Fiat master cylinder remote reservoir hose adaptors (which to my amazement worked so well in fact that it turned out to be very simple) to remote reservoirs from OBP - these have a reputation for leaking and yup, I have a slow drip drip leak from them so am now researching suitable replacements. 

All of that said, was it worth it - I'll only be able to tel you once I am on the road/track, but for now if the peddle does what I want it to do and thats to stop the car with a better feel, then yes. Watch this space.

Just one complaint, with myself really, I fitted everything before priming the master cylinder thinking it would prime by filling - nope, this has been a lengthy process. Mind you, I changed from DOT4 to 5.1 so the 4.5 litres of brake fluid I have used completely flushed the entire system several times over. I do now have a peddle, thank goodness allowing me to finalise the other stuff before MOT.