Late model cars with dual circuit master cylinders used metric unions in 2 different sizes for the master, the rearmost one being a "standard" metric male and the front one being a fatter metric male, the latter having the 13mm hex head and the former an 11mm hex. The fat ones are also used on various french cars in the rear cylinders and are readily available from motor factors.naskeet wrote:For the past 20~25 years, I have contemplated the possibility of upgrading my 1974 Triumph Toledo 1300, with dual-circuit brakes, for the purpose of increased safety margin, in the event of hydraulic brake-system failure. I’ve never suffered complete brake failure, but I’ve known a few people who have and I don’t relish the prospect!
With this in mind, I had at some time during the late-1980s or early-1990s, salvaged the dual-circuit hydraulic-brake master cylinder, differential-pressure-sensing unit (PDWA!?!) and dashboard warning light, from a late-model Triumph Dolomite 1300 (1979/80 | V-registration | Chassis No. TWAL A1 AT 100038); equipped with a single SU carburettor.
Having no workshop manual, containing details of Triumph Dolomite (especially late-model!) braking systems, I took the precaution of drawing a sketch of the brake-pipe connections to the dual-circuit hydraulic-brake master cylinder and the differential-pressure-sensing unit (PDWA!?!). However, I was unable to determine whether the configuration of hydraulic pipework and connections, otherwise differed from those of the single-circuit hydraulic braking system. I also failed to note the exact position of the differential-pressure-sensing unit (PDWA!?!), which might possibly be identical to the four-way union connector, used for the single-circuit braking system!?!
I also noted that three different sizes of male brake union are used, having three different fine & course thread sizes, but only two hexagonal “bolt-head” sizes. What are these thread sizes? Are some metric, Imperial UNF, UNC or otherwise?
The smaller hexagonal “bolt-head”, appears to be either 7/16 inch AF (i.e. 11•11 mm) or 11 mm AF, on which both my Imperial and metric brake-pipe spanners seem to be a snug fit. The larger hexagonal “bolt-head”, appears to be of 13 mm AF, on which my ordinary 13 mm AF ring-spanner & socket will fit, but neither my 1/2 inch AF (i.e. 12•70 mm) sized brake-pipe spanner, ordinary ring-spanner or socket will fit. What other sizes of brake-pipe spanner exist?
My present set of brake-spanners are as follows:
Williams Superslim UNIMIL110 – hexagonal-section 10 mm & 11 mm AF
Williams Superslim UNI78 – hexagonal-section 7/16 inch & 1/2 inch AF
Williams Superslim ADJ45 – square-section 1/4 inch & 5/16 inch AF
Being unfamiliar with the three different sizes of associated brake-pipe unions, I also salvaged these for reference purposes, and as a convenient means of sealing the units. Once I got the units home from the car dismantlers, they were disassembled, cleaned (externally & internally – using isopropanol; otherwise known as propan-1-ol or propyl alcohol), lubricated internally with Automec silicone brake fluid and reassembled, before storing them away for future use.
Noting that the dual-circuit hydraulic-brake master cylinder was much longer than my Toledo’s existing single-circuit hydraulic-brake master cylinder, which would preclude retention of my Toledo’s existing air-filter housing, I also salvaged the very different looking air-filter housing, from the Triumph Dolomite 1300. After refurbishment, I then retro-fitted it to the Toledo during its scheduled 84,000 mile service (84,069 miles | 6th July 1991), together with a new Wipac AP34 (equivalent to Unipart GFE1005) air-filter element. These air-filter housings & associated air-filter elements, are also used on some Morris Marina 13/1800s.
http://www.rimmerbros.co.uk/Item--i-12G3590
http://www.rimmerbros.co.uk/Item--i-GFE1005
http://shop.aseriesspares.co.uk/shop/re ... ter-round/
Several years later, in exchange for a modest donation to the Firemen’s Benevolent Fund, I took the opportunity to salvage various parts from a late-model Triumph Dolomite 1500 HL, at my local fire station (opposite my home), which they had used for practising rescue techniques. This included an additional dual-circuit hydraulic-brake master cylinder and differential-pressure-sensing unit (PDWA!?!), plus the associated larger-girth vacuum brake servo unit, which I had been unable to salvage several years earlier, from the late-model Triumph Dolomite 1300.
My Toledo has stood unused (SORN declared annually) since mid-1999 (i.e. 16+ years), but circumstances have changed, and it is likely that I will need to have use of my own daily-driver car in the future, so I’ve embarked on a major programme of refurbishment and rejuvenation, which will inevitably involve disassembling and overhauling the entire hydraulic braking system. Hence, this would be a golden opportunity to upgrade the system to dual-circuit, whilst the other work is being done; including replacement of all the metal pipework.
It had been noted in the mid-to-late-1990s, during servicing and annual MOT inspections, that some of the metal brake pipes in exposed positions, were beginning to show signs of superficial external rusting and that I might need to replace them in the foreseeable future. Since then, the rusting has become more extensive, so I shall replace all of the steel pipework with Kunifer-10 pipework (an extremely corrosion-resistant cupro-nickel alloy, comprising 90% copper & 10% nickel, that should outlast the life of the vehicle | became standard a few decades ago, on Swedish built vehicles!), as I did during the winter of 1988/89, when I refurbished & upgraded the dual-circuit hydraulic braking system of my 1973 VW “1600” Type 2. I shall similarly be using DOT 5 Automec silicone brake fluid.
Home Forums > Help and Assistance > Bay Tech Clinic > Steering, Brakes & Suspension > Retro-fitting remote-acting brake servos, Kunifer-10 pipework & silicone brake fluid
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After much searching, I finally found my little-used set of Moore & Wright, 0•25~3•0 mm metric screw-pitch gauges (vaguely resembles a large set of 2 x 15 feeler gauges, with serrated edges similar to saw blades), which enabled me to confirm that both of the brake-pipe unions to the dual-circuit master cylinder, have metric screw threads with a 1•0 mm pitch.Carledo wrote:Late model cars with dual circuit master cylinders used metric unions in 2 different sizes for the master, the rearmost one being a "standard" metric male and the front one being a fatter metric male, the latter having the 13mm hex head and the former an 11mm hex. The fat ones are also used on various french cars in the rear cylinders and are readily available from motor factors.
The five (2+3) male brake-pipe unions [all with 7/16 inch AF (i.e. 11•11 mm) or 11 mm AF hexagonal “bolt-heads”] on the PDWA, are of two different thread diameters and pitches, for the front and rear brake circuits.Carledo wrote:The unions on the PDWA are a complete 1 off and are POSSIBLY 3/8 UNC though they could easily be BSP. Whatever, my factors couldn't match them when I converted my Toledo to dual circuit so I salvaged them from the donor cars pipes and flared them onto new copper.
Carledo wrote:Getting all this into service was a nightmare with bleeding being obstructed by the PDWA and then re-bleeding to get the light off (I had gone the whole hog and wired the PDWA warning light into the handbrake light on my Nova dash)
Once in service, the PDWA proved erratic in operation with the light coming on sometimes and not others, sometimes staying on and other times going on and off with brake application until I got completely fed up with it and disconnected the lead from the PDWA switch. The brakes were fine with no loss of pressure or fluid.
Later I found that the rear brakes were a tad too powerful since I had not used the Sprint LSV with my Sprint rear brakes and at this point removed the PDWA (which was redundant anyway) and replaced it with a simple brass 3 way union for the front brakes and a pressure control valve from a 2.0 ltr Cavalier for the rear circuit (A simple double female inline joiner would work just as well if you don't need the PCV) This meant changing all the unions again on the 5 pipes that had connected to the PDWA, but at least they were swapped for unions that are readily available.
IMHO the PDWA is a waste of space and to a large extent, negates the purpose of dual circuit brakes, since having separated out the front and rear brakes at the master, they are then joined together again by the PDWA! So a failure in the PDWA (possible if not particularly likely) would still leave you with total brake failure, it happened to me on a MkI Cavalier which had a similar device!
My advice is "leave it off!" Possibly you could find a cap from another scrap car with a built in level sensor and use the wiring on that instead.
If you want to be REALLY anal about it, it wouldn't be TOO difficult to arrange a diagonal split dual circuit system to mimic modern practice, it would just be needful to run a duplicate front to back pipe and a second rear flexi hose, but I have stuck to the F/R split and it's worked fine for me in 4 years of hard driving.
Carledo wrote:Late model cars with dual circuit master cylinders used metric unions in 2 different sizes for the master, the rearmost one being a "standard" metric male and the front one being a fatter metric male, the latter having the 13mm hex head and the former an 11mm hex. The fat ones are also used on various french cars in the rear cylinders and are readily available from motor factors.
Here are three brake-parts suppliers, who seem to stock M12 x 1•0 mm male brake-pipe unions.NASkeet wrote:When I track down my little-used micrometer, I will later confirm their diameter, but using my adjustable spanner as a crude set of calipers, in conjunction with my metric rule (i.e. cm & mm), the "standard" metric male and fatter metric male unions, appear to be of 10 mm and 12 mm diameter respectively. Hence it seems the two male brake-pipe unions, are of sizes 10 x 1•0 mm and 12 x 1•0 mm
Yes indeed, from an early SR Nova (or Corsa A if you like) This one:-naskeet wrote:
When you speak of a “Nova dash”, is that by chance a dashboard originating from a Vauxhall Nova, otherwise known as an early-model Opel Corsa!?!
I shall give some further thought to the inclusion of the PDWA, which seems to be a less than desirable way of sensing a significant hydraulic pressure difference between the two circuits.
My 1973 VW “1600” Type 2, with factory-fitted ATE – Alfred Teves, dual-circuit brake master cylinder, has a pair of 3-terminal, hydraulically-activated brake-light switches (have M10 x 1•0 mm tapered screw threads), whose electrical design also activates the brake-circuit-failure warning light, if there is insufficient pressure in one hydraulic circuit, to activate the brake lights.
Hence, one could omit the PDWA and substitute two M10 x 1•0 mm female T-piece connectors, together with two Volkswagen-Audi, 3-terminal, hydraulically-activated brake-light switches.
As you indicated, it would be a relatively simple matter to modify the braking system, to create a front & rear diagonally-split configuration, but I wonder how such a modification (non-standard for either the Toledo or Dolomite), would be regarded by motor insurance companies!?!
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