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MG Midget and Sprite Technical - 1500 brake cylinder

Hi there

Looks as though I need to replace the brake cylinder on my 1500 78 midget. Couple of questions:
- what's the general view on use of dot 3 or dot 4 (concluded can't use dot 5)? I need to top it up until the fix is made and don't know what dot I have in it (not been replaced since I had it). Read a lot online and lots of views. Handbook obv says dot 3 but that was 34 years ago!
- the current cylinder is the master cylinder Brake GMC166, of which I can't find the same part. Are the newer tandom ones ok?

Many thanks
bk dyson

AFAIK you'd be ok putting fresh DOT 4 or DOT 3 as a top up to old unknown condition DOT 3 or DOT 4 fluid you already have in there

but do you really need to top up can't it wait

DOT 4 has been used in our cars for a few years now I think - others will say if I'm wrong about that - my car has DOT 4 in

I'm not sure if DOT 5.1 can be used or its expense

- - Dry boiling point - - - - Wet boiling point
DOT 3 205 C (401 F) - - 140 C (284 F)
DOT 4 230 C (446 F) - - 155 C (311 F)
DOT 5 260 C (500 F) - - 180 C (356 F)
DOT 5.1 270 C (518 F)-- 190 C (374 F)

it is very important to thoroughly flush out all the current fluid as it could have a lot of water in it, you want it all out and fresh fluid in (every 18 months by the book)

as regards the MC, wait around or check the Archives as this was discussed fairly recently I think
Nigel Atkins

hi dot 5 cannot be used as doesnt mix with 3 or 4, so taking the risk that its 3 or 4 i have to go for them!

i do need to top it up as its leaking from the cylinder and starting to get low, that way i wont run out of fluid and have no brakes

so i cant use the other part?
bk dyson

Sorry Brad I must have overwritten on that bit, no DOT 5 can't be used as its silicone based and the others are not

I also see I didn't put about the crud to be flushed out as well as water

number one most important system on the car is brakes, effected by tyres (and suspension) more than many realise

thinking about it as DOT 5.1 is not silicon it probably could be mixed with 3 or 4

as for the MC if no one else comes along then do an Archive search as I'm sure there was info on this recently
Nigel Atkins

This thread was discussed between 29/04/2013 and 30/04/2013

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