3 replies to this topic

[mowog46]

Hi everybody, I am new to this forum and would like some general advice. I have, perhaps rashly, offered to recommission by daughter's 1979 Mini City and return it to the road.. It's a peach of a car, she bought it 20 years ago from it's first lady owner, ran it for a year and then retired it to my barn, where it has sat ever since. Unsurprisingly, all the wheel cylinders were seized and the flexible hoses collapsed. I have replace all of these (six wheel cylinders and four flexibles). The car has the dual circuit front/rear split braking system and the existing master cylinder is the type with a switch which I believe monitors the brake pressure equaliser, which is mounted on the bulkhead. It is NOT the master cylinder with a switch in the cap. As I am intending to change from Glycol based dot 4 brake fluid to Dot 5 Silicon fluid I would like to replace to master cylinder as well as the rest of the braking system. The current master cylinder is currently no longer available ( though a repair kit is available). I would prefer to fit an all new cylinder, so my question is: can I fit the later type cylinder? - I think the number is GMC227. I understand this cylinder has metric connecter threads, but otherwise it looks identical, so if I put the correct metric connectors on the brake pipes will it be a straight swop, using the existing mounting points. If I then change the existing electrical connection to two spade terminals that will connect with the cap, will everything work as intended? 

I have also seen the terms Yellow Tag and Black Tag in relation to these master cylinders, can anyone tell me what the difference is?

Thanks for your patience in reading this.

[nicklouse]

My first question is why the change of fluid? The service intervals are the same. As it is not missable with water, it is also an open system so any water that enters the system will sink to the lowest point causing rust rather than being absorbed by the liquid.

 

as to any MC you fit check that the seals are compatible as many are not.

[Spider]

I've not seen a Tandem Master Cylinder for our Cars that has a Tin Tank. Can I trouble you to post a photo ?

As best I know, in that era, the Master Cylinder for the Tandem Brakes was the GMC167, which is currently available. Some incorrectly list them as being for diagonal split, which they were used for, but they were used in front rear split too.

I get your thinking on going to DOT 5 fluid and on paper, it sounds glamorous. I have one car on DOT 5, which I filled it with when I restored it some years back. I've restored many since, using DOT 4 on these. I don;t feel the expense is warranted and if not done with high care, the pedal will end up quite spongy. Using this fluid does not get around the recommended rubber change out at 3 years / 40 000 miles. I note too that many Brake Parts manufacturers specifically don't recommend it and will void any warranty of their parts if it's used. Even Harley Davidson have gone away from it, though that maybe a cost cutting measure.

[nicklouse]

I've not seen a Tandem Master Cylinder for our Cars that has a Tin Tank. Can I trouble you to post a photo ?

As best I know, in that era, the Master Cylinder for the Tandem Brakes was the GMC167, which is currently available. Some incorrectly list them as being for diagonal split, which they were used for, but they were used in front rear split too.

I get your thinking on going to DOT 5 fluid and on paper, it sounds glamorous. I have one car on DOT 5, which I filled it with when I restored it some years back. I've restored many since, using DOT 4 on these. I don;t feel the expense is warranted and if not done with high care, the pedal will end up quite spongy. Using this fluid does not get around the recommended rubber change out at 3 years / 40 000 miles. I note too that many Brake Parts manufacturers specifically don't recommend it and will void any warranty of their parts if it's used. Even Harley Davidson have gone away from it, though that maybe a cost cutting measure.

To add to this the US Army has been trying to work out how to change away from this for years but have not worked it out yet.