Clutch and brake - shared fluid reservoir

My Atmo's been fantastically reliable for the last 14 months - but it had to end sometime I guess. Now my daily transport, the car's crawled along in heavy traffic on the A1 almost every work morning for the last three months. On the way home tonight though, lots of gear crunching and just about limped home I had to switch of the engine, select reverse, and then start her again to get on the driveway and basically have no gear change now

The car's losing fluid somewhere - interested to understand how it all works and I'd like to fix it myself rather if I can (best way to learn). So...

From the service manual I see that both the clutch and brake systems use the same fluid from the same reservoir. 'Fraid I don't really understand much about how clutch/brake master cylinders work and I've not seen a shared system before - does that mean that a leak in the clutch hydraulics could mean loss of brakes, or vice versa?

Or is there some sort of one way valve setup so that fluid doesn't flow back to the reservoir once in the clutch or brake cylinder/pipes? So a problem in one system can't affect the other. Makes sense to me that there must be something like that- else they'd have to use separate systems for safety??

Thanks.

SS

The reservoir is split in two with a supply to both front and rear brakesystems and clutch

When did the fluid last get changed ?

Probably a case of old fluid thats absorbed too much water so efficiency has decreased.

I know that on early turbo models the clutch pipes were located too close to the turbo / exhaust with the result of heat transfer on to the clutch lines. Makes changing gear when stinking hot a real challenge!
Not certain if this is the case with atmo.

Fluid loss. Check the master cylinder seals, probably more likely than anywhere else.

Forgot to mention that if you do change the fluid then make sure that as well as bleeding the fluid through the brake calipers that you also bleed off via the clutch slave cylinder. Otherwise the fluid in the clutch line wont be replaced with fresh.

Thanks guys.

Re: fluid change - don't know. The car had a new clutch approx 18 months ago so hopefully it was changed then. Job for the weekend to check it all out and at least try and find out what's broken. If nothing else I've got to try and get her driveable because she's booked into a garage for next friday in case I can't sort her myself.

I'm still a little unclear about how the brake and clutch hydraulics are linked. From the top it looks like a single reservoir so does it split into two further down? Are the two systems completely seperated by the split reservoir so a leak in one doesn't drain the other?

Probably sounds like a really basic question but although I do most work myself I've never touched hydraulics. I guess that, as the reservoir is plastic, it's low pressure so once fluid is sucked into the master cylinder it stays there. Would that be right?

Thanks again.

SS

I think your assumption is correct, the resivoir shares the same fluid, but there is probably 2 outlets (1 for clutch system and 1 for brake system) and at the very bottom of the resivour there is probably a low partition..... so that if one system springs a leak, the other system is not completely deprived of fluid.

The point is, if you want to change and refresh all of the fluid in the resivoir, then you need to bleed all 4 brakes PLUS the clutch slave. This will then expell ALL of the old fluid from all pipes as well as the resivoir.

Just because the clutch was changed, there is no real reason to change the fluid unless all the 4 brakes are bleed through too. I'd guess that most general garages would just top up the resivour after bleeding the cluth slave.

Bleeding the clutch is likely to improve your gearchange. I used a Gunsons Ezebleed kit, it worked very well and you can do it on your own without a helper.

Also, check the pedal mechanism. There is a pin with retaining spring which goes through the clutch pedal. It is also in a plastic sheeth. The plastic sheeth will have broken in half (they all do) PLUS the pin may be very badly worn, and so now you are getting a lot less pedal travel. This is worth checking too.

The resivoir is devided one section for the clutch one for the brake in all there are three outlets from the resivoir clutch front and rear brakes a loss off fluid would indicate ether master or slave cylinder check these first then look for a broken clutch pin the tube under the car is plastic so well worth a look too

When did the fluid last get changed ?

Probably a case of old fluid thats absorbed too much water so efficiency has decreased.

Tried to bleed the system and get some new fluid in there. I managed to push old fluid out but no new fluid was sucked in from the reservoir. Does that mean the master cylinder is the problem?

I can't see where fluid is being lost from though. There's a very slight seepage where the plastic pipe joins the slave cylinder, but that's all I can find. Maybe because there's no pressure it's not apparent where the leak is.

How did you bleed the system, manually or using a Gurlsten bleed easy ?
The 'bleed easy' is carried out under pressure - uses a spare tyre to pressurise the resevior to assist the bleed proceedure.

Manually - with a "one man" clutch/brake bleeding kit from Halfords - really just a piece of plastic pipe with a one way valve at the end.

Loosened of the bleed nipple approx' half turn, attached the kit and pumped the clutch pedal slowly.

What's the best way to get the car high enough off the ground to get to the master cylinder properly? With the car jacked up at the side chassis jacking point I can't get far enough under. Where is it safe to support the weight of the car with axle stands at the front?

Thanks.

There is no reason why they would have checked or changed the fluid when they did the clutch change. So the reason for the low fluid is most likely just brake pad wear. A leak is unusual, but easy enough to spot by looking at the master cylinders and the brake calpers. The outlet for the clutch fluid from the reservoir is about half way up the side of the bottle so it is always the clutch that goes first, not the brakes.
If the clutch hydraulics have got air in it can prove tricky to bleed just by pumping the pedal and hoping the one way valve on the bleed pipe works to stop air being sucked back in. A pressurised bleed kit is better. Otherwise one person has to pump the pedal, the other closes the nipple with a spanner each time the pedal is lifted up...

Agreed ,get a Gunson .It's always comes back if you don't pressure bleed the system .

If the clutch hydraulics have got air in it can prove tricky to bleed just by pumping the pedal and hoping the one way valve on the bleed pipe works to stop air being sucked back in. A pressurised bleed kit is better.

Thanks for the advice. Dead right!

I couldn't find a Gunsons bleed kit locally and really needed to get this sorted so bought a Sealey hand vacuum pump kit today. That worked like a dream and I have a working clutch again

Easy job with the right tool - now just need to find where the fluid leaked from in the first place.

Certainly the fluid level will drop with brake pad wear, but more likely is that the fluid is coming out where the piston is moved by the pushrod attached to the pedals. Undo the large cover over the lower pedal assembly and you will most likely find your leak.

Clutch and brake master cylinder replacement though is a bit of a job and much more easily done if the fuel tank is removed, so I have found. Do both whilst you are there.

I found the slave cylinder was leaking.

Replaced - and all was OK.

For a few weeks......

Now the master cylinder's given up