brake union sizes

[T100SS]

I just tried fitting a servo to a 71 traveller. Had to buy parts on line (am in S Yorks). The three-way union (servo - front - rear brakes) has two different threads, I since learned. BSf x2 plus one UNF coarse.

It is the coarse thread I'm having bother with. It is supposed to be the same as the rear master cylinder outlet - and indeed the rear brake pipe male union should fit.

I just undid the pipes and the rear brake pipe that came out of my recently fitted master cylinder does not fit the three-way union - anywhere. Which is odd since the coarse unf nipple I was supplied has gone into the rear master cylinder ok (this is to blank off the rear master outlet).

If anyone can make any suggestions, like where I can get a three-way PLUS the male unions to fit, I'd be grateful. Meanwhile, I think I'll rip the servo off as this leaves me carless.

[simmitc]

The split between front and rear brakes is a new component introduced when fitting the servo - previously there was one line running to the rear from the back of the master cylinder, and another to the front from the side of the m/c. Now you should have a blanked rear from the m/c plus the side pipe leading to the servo, then your new splitter. This three way union is nothing special. Perhaps the supplier has given you a metric one, or using the wrong thread has damaged the fitting so that now neither thread will work? The imperial ones will be either 20 tpi or 24 tpi. Don't try re-tapping the threads, brakes are too safety critical.

You can purchase matching union and connectors from from Vehicle Wiring Products. or use the fitting as supplied for the rear axle - that might have different threads for the two metal pipe connectors and the flexible hose. Just make sure that everything fits together before fixing it to the car.

[bmcecosse]

Servo on a small car like the Minor is completely unnecessary....and as you have found - not easy to install. There is no UNF 'coarse' - that would be UNC !! The threads are 3/8" UNF and 3/8" BSF. The BSF thread is more 'coarse' than the UNF. The unions MUST NOT be mixed up! The pipe that was screwed into the master cylinder rear port for the rear brakes would be BSF. I can only assume they have given you pipes with 3/8" UNF threads to make the connections to the T piece. Where do they tell you to connect the T piece??