My brakes have been gradually rubbish for ages like air being very slowly drawn in over time.
Tonight I think I've found why. It seems that the seals where the reservoir meets the master cylinder body on my Mk.1 Fiesta MC are weeping.
Does anyone know if this reservoir will pull off and the seals looked at or even better the reservoir pushed tighter into the main body or is it a cae of buying a new item?

should pull out of the seals they are a bit tight though

Should just pull out... but I've never seen one leak. Any leak of fluid out of that seal will cause the fluid level in the res' to drop but not introduce air into the cylinder (untill it's empty anyway).

adrian

It's wierd. The brakes get worse to the point of the pedal hitting the bulkhead in the space of like 5 months or so. A quick bleed of them makes them all fine again and the only leak I can find at the moment and I've been looking on and off for months is where the reservoir fits into the body. You can see fluid there and also whats looks like a touch of surface rust and if I'm not mistaken there seems to be a touch of water in the reservoir. There's a drip on the top of the inside, a bit like there's been condensation in there.

When you bleed the brakes, where and when does the air appear? Is the air there strieght away or does it take a while to come through? Do you get more air at one bleed nipple or are they all similar?
I've seen pipe connections, master cylinders and caliper/slave cylinders, draw air in, without leaking fluid out.

adrian

Generally only get air at one of the wheels and it comes out after a little bit of fluid. I tend to go for the front wheels as they're just easier.

Then it's unlikely to be that caliper (could be) but more likely to be further up the line.
Given the unusual leak at the res' seals I'd start there. If the seal is poorly seated and blocking the holes to the master cyl' then that could cause it to suck air past the cyl' seals instead of fluid from the res'.

Drain the res' and it should then just come off with a pull and a bit of a wiggle. You could always bring it down here on Sat morning if you want and we'll have a look on the ramp.

adrian

I've got the morning to myself so I'll have at look at it shortly and see but thanks for the offer matey.

Description

This is what it looked like. Obviously something going on there. I removed the seal and cleaned that up and put it back together. Just waiting for the missus to finish work so I can borrow her foot and bleed the brakes (bloody Easi Bleed has got a broken cap) and we'll see.

Hard to tell from the picture but those seals look odd. There's usually more of a lip at the top than appears there. Could they have pushed in with the res'?

adrian

How much is a replacement master cylinder? It could be easier to just buy a replacement.

Seals are a kind of big mac shape with the two rings around the middle that sit into a groove in the body and fit flush to the body.
I've cleaned up and refilled the system but now found the rear n/s caliper piston stuck so that'll have to come off now!