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Brake fluid leak

JoelP - 4/6/24 at 07:21 PM

Evening again. I've noticed my brake fluid is dropping onto my exhaust. It appears to be leaking from where the plastic reservoir joins the metal master cylinder. Any idea what causes it, and indeed what donor car this is from? Quite rare I believe, the fact that I've got the servo too. Photos in following post cos I forgot to upload first!

JoelP - 4/6/24 at 07:23 PM

Locost master and servo

JoelP - 4/6/24 at 07:24 PM

Leak just visible. It drips until empty.

The leak

JoelP - 4/6/24 at 07:31 PM

I think it's from a Sierra. I can only see 3 brake pipes though. Will there be a 4th outlet plugged? It's back under its tarp now.

cliftyhanger - 4/6/24 at 07:36 PM

The resevoirs are usually a push fit with some rubber seals. So they may have called it a day, or a crack in the resevoir.
Take care as brake fluid is highly flammable, worse than petrol.

JoelP - 4/6/24 at 07:39 PM

Thanks, I didn't know that! It's smoked loads as it burnt it off!

adithorp - 4/6/24 at 08:58 PM

quote:
Originally posted by cliftyhanger
The resevoirs are usually a push fit with some rubber seals. So they may have called it a day, or a crack in the resevoir.
Take care as brake fluid is highly flammable, worse than petrol.

Yes, you deginatly don't want it dripping on a hot exhaust. Pretty low flash point. The zip tie is to stop it coming off in a shunt and causing a fire.

I guess it'll either be a perished rubber seal or maybe corrosion between seal and master or a cracked reservoir.

jps - 5/6/24 at 09:45 AM

Doesn't look exactly the same as my Sierra brake res (which looks like this:

)

But there may be different versions over the years of production?

[Edited on 5/6/24 by jps]

gremlin1234 - 5/6/24 at 12:31 PM

apparently the mounting seals come with a master cylinder repair kit. item 6 in the pic below
https://ford.7zap.com/en/car/63/6.46050,13.35344/0/1888/16875/73219/

nick205 - 5/6/24 at 12:35 PM

Looks very similar to my Sierra brake setup

Rescued attachment img_3.jpg

Individual ports for each front brake and a single port to the rear that was then "T" split to the rear wheels.

JoelP - 5/6/24 at 02:37 PM

Thanks everyone! I'm pretty sure mine is plumbed differently to yours Nick. Rear brakes connected to front top outlet. Should this be rectified?!

nick205 - 5/6/24 at 03:25 PM

quote:
Originally posted by JoelP
Thanks everyone! I'm pretty sure mine is plumbed differently to yours Nick. Rear brakes connected to front top outlet. Should this be rectified?!

Can't advise if you should change the way yours is plumbed in.

From memory I plumbed mine as it was in the donor Sierra before I removed it.

Also from memory (not in the image) I added a rerar brake valve limiter (from a Fiat Uno) in the rear brake line. Purpose was to prevent rear wheels locking up before the front wheels.

The car passed it's SVA and subsequent MOTs with this setup.

[Edited on 5-6-24 by nick205]

SteveWalker - 5/6/24 at 09:54 PM

There was a similar valve on the Sierra, that's the one I used.

SteveWalker - 5/6/24 at 09:57 PM

quote:
Originally posted by jps
Doesn't look exactly the same as my Sierra brake res (which looks like this:

)

But there may be different versions over the years of production?

[Edited on 5/6/24 by jps]

Very likely. Certainly mine is exactly the same as the OP's picture, although the master-cylinder is different, with that one looking very smooth and almost like a fabrication from tube, while mine is much rougher and much more obviously a casting.

adithorp - 6/6/24 at 09:45 AM

Ford swapped from cast to fabricated brake masters sometime towards the end of Sierra production.

nick205 - 6/6/24 at 12:37 PM

quote:
Originally posted by adithorp
Ford swapped from cast to fabricated brake masters sometime towards the end of Sierra production.

My donor Sierra was a G plate Sierra Saphire saloon (MOT failure due to rotten floor)

JoelP - 13/6/24 at 03:20 PM

Thanks everyone. I ordered the seal kit off eBay, swapped the two big ones, and it appears to be fixed. Went for a spin to burn the spillage off, and got caught in torrential spitting. Well, it felt torrential at 60 with no wipers