Technical Seicento brake behaviour

[oldalan]

Hi. Apologies if this has been covered before and I havn't found it, but I drive a '52 plate 1.1 mpi sx and am experiencing some odd brake behaviour which I think is down to master cylinder seal or valve issues.

When I brake, the car stops normally. But if holding in a queue say, and I ease slightly off the pedal, it then goes right to the floor, quite quickly - same rate say as if I was pushing the pedal with no vacuum in the servo, then started the engine. I think fluid is leaking past the seals or top up valve when I ease off.

I had something a little like this in my old galaxy, which was down not to the master cylinder being faulty but the calipers distorting because the pressure was so high. So I've learnt how important it is to check before diving in, especially when you're as broke as I am.

I've seen a post to do with the master cylinder seals flipping when pistons are pushed back in; can't remember doing anything at the same time as this started but may have done. Is this a possible cause? Anybody recommend a a good overhaul kit?

Thanks very much in advance for any advice.

 

[fingers99]

There really isn't much point in overhauling unless the prices of the master cylinder have gone up considerably since I last did one. Compare the price of an overhaul kit on brakeparts.co.uk with the price of a new one from them or eurocarcare.net or your local factor.

 

[oldalan]

See what you mean - just been on ebay. I haven't had to do a m/c for about 30 years - prices seem to have come down a lot since then! Hardly anything in it so might as well get a new one if I need one. Any thoughts on if I do?

 

[fingers99]

I did a guide, but it didn't make it into the guides. Let's see.......... No, can't find it. Hard bit is prising the reservoir off the master cylinder (careful use of pry bar).

Fairly well documented in the Seicento Technical Manual (downloads). 11mm brake spanner, I'm now a convert to cheapo vacuum bleeding using a Mityvac - alike (£20 or less on eBay).

 

[Eklipze3k]

I did a guide, but it didn't make it into the guides. Let's see.......... No, can't find it. Hard bit is prising the reservoir off the master cylinder (careful use of pry bar).

Fairly well documented in the Seicento Technical Manual (downloads). 11mm brake spanner, I'm now a convert to cheapo vacuum bleeding using a Mityvac - alike (£20 or less on eBay).

Was this what you were looking for?

 

[oldalan]

That's handy to know. Had vac pump on my list of handy things to get (my other car has a couple of vac operates bits as well as abs brakes.Do you think it is master cylinder? Feels like that to me but unusual things have caught me out before... The guide is good to have - just like oldish tim(old times single circuit tin reservoir - really old times cable brakes - - and really really old times not front brakes at all!)

 

[fingers99]

Master cylinder is most likely. I remember that the car would stop fine, but would then if on an incline, slowly start moving forward or backwards.

 

[oldalan]

Thanks very much guys. I feel a lot more comfortable that I'd doing the right thing and it shouldn't go too far wrong or have to spend a fortune now. I have pads, disks and shoes to fit too, so looks like I'd better order up a cylinder and get some brake fluid and maybe a vacuum pump. I do have a pressure bleeder somewhere and a couple of old one-way bleeding kits but vacuum seems a better way to go if I can scrounge up the £20 quid.

Thanks again for the very speedy and comprehensive help. I'll be back