Master Cylinder Repair.

[Chris Morley]

Having finished the welding on my 'free' traveller I found today that the pedal went right down to the floor and I only had the handbrake to prevent disaster when the car came off it's ramps. Some two months ago I had bled the brakes and they worked fine at the time, however the pressure is now gone. On reflection the bubbling I noticed at the time (in the M/C fluid reservoir) while pumping the brake was a big clue. A quick investigation today (just before the heavens opened) revealed clear evidence of brake fluid staining the ground under the chassis leg (containing the Master Cylinder).

So far, so obvious. It looks like the M/C will have to come out unless the leak turns out to be from a brake pipe in the chassis leg, which I guess is unlikely. Should I just buy a new M/C, or wait until I can examine the old one in the hope that it can be sorted with a repair kit? Is it likely that the leak is simply caused by a defective rubber seal? And how often are old Master Cylinders repairable with these kits?

[Gareth]

Well, when the cylinder leaks it's often caused by pitting on the insides of the bores, which would make getting a proper seal nigh on impossible, even with a new seal kit. If the seals have gone, it won't be long before the humidity ingress will cause the bores to become pitted, thus leading to... &c.

Master cylinders are pretty important, really, aren't they, and for £50 I'd fit a new one, just for piece of mind.

[57traveller]

What a bummer Chris but I agree with Gareth. If the leak is from the M/S itself and not a pipe union then as the thing has to come out anyway you'd be well and truly peed off if it still leaked after just renewing the seals etc. Only to have to remove it again and replace the whole thing (at least it would come out easier the second time!!). £50+ is a lot compared to the cost of a repair kit but think of all the wasted time if it had to come out again. You should get some clue as to where the leak is after taking off the cover plates anyway.
Good luck, it's not the pleasantest (is that a word?) job at the best of times.

[Gareth]

If it's not the plesantest (not strictly a word, but it should be! ) job in the world, then why do it twice? The way I look at it - brakes are important, so there's no point in messing with them - get it done right. My MC failed, and I had a new one fitted. All is fine now.

I wonder how much an MC on Ray's Porche would be?

[57traveller]

I suppose it should be most pleasant???


Totally irrelevant but on the subject of parts prices, I heard of a person who needed new brake wheel cylinders for a Porche and went along to their friendly main dealer and was quoted some ridiculously high price ( they must have been gold, yes that much! ).
He declined and decided to go along to his local non franchised garage to ask their advice. An old mechanic, on seeing the wheel cylinders said "I recognise those, same as fitted to a VW LT van, I can get those for £20 each" which he did!!! Sorted.

[Gareth]

I suppose that's one good thing to come out of VW's world domination...

[Kevin]

Should I just buy a new M/C, or wait until I can examine the old one in the hope that it can be sorted with a repair kit?

Chris the repair kits are really for just replacing the rubbers and piston if things are just deteriorating/perishing a bit like the small problem Willie had with his front cylinders, if you have quite a large leak which it sounds like it is replacement is the only option.
Bull Motif have Lockheed ones for £43:95 + at the moment

[Chris Morley]

Thanks to all for the replies - it confirmed what I thought likely (ie: replacement is necessary). I'll go out and have a look under the cover panel this evening just to make sure it's not a break in a pipe. Kevin - I'll probably use Chertsey Minors as their prices match those of ESM, Bull Motif etc. and I'll be able to pick up the M/C from them.

There's a lesson in the VW pistons for a Porche story - many items in expensive or exotic cars are bog standard items so it pays to do a little research to avoid rip-off specialist prices. It reminds me of the furore a few years ago when a Motoring journalist noticed that the new top of the range Aston Martin shared dashboard buttons and door handles with a Fiesta....

[Gareth]

Check the quality of the MC. I've heard that the Lockheed ones can give trouble when it comes to blee ding the brakes, because the design / manufacture has altered slightly in recent years.

I had a unipart one fitted, but there was no baffle in the cap - under any braking, the fluid would squirt from the tiny hole in the cap. A couple of spring washers cured the fault, though. However, I'm keeping my eye on it.

Just something to be aware of...

[Willie]

Chris...since it has to come out,now would be a good
time to replace the rust prone brake pipe which sits
in the chassis leg to supply the rear brakes,with a
nice copper one...if you haven't already done it?

[Chris Morley]

Willie - an extremely good point which I hadn't thought of. Thanks for thinking of it . I've heard a few horror stories about brake failure due to this pipe rupturing (because of corrosion). I will probably do this at the same time as I clear out the gunk in the chassis leg. When I looked this evening I could not see where the fluid was leaking from but the bottom of the chassis leg was damp and there was a slight squelching sound when the brake pedal was depressed.

To be honest I've been too busy dealing with the MOT failure points to think about the long term rebuilding of the car. The aim was to have a scruffy but roadworthy back-up for my saloon, but I hadn't reckoned on having to replace the Master Cylinder. As my saloon is pretty much sorted (except for cosmetics) I should be able to give this traveller more attention next year.

[Kevin]

A couple of spring washers cured the fault

Gareth where were the spring washers placed and how did it help your problem.
Also I had not heard of problems with the Lockheed cylinders as they are original equipment, I wonder where the Unipart ones come from.

[Gareth]

The spring washers fitted inside the master cylinder cap, along with a couple of normal washers. This seems to be acting like a baffle (which I think should be fitted) and has stopped the fluid squirting out. It made no difference when blee ding the brakes, so I reckon it's OK now.

The Unipart ones were manufactured from the same drawings and specs as the Lockheed ones, but I'm told that the Lockheed ones are different, due to irregularities inside. Can't say I understood all of it, to be honest, but I do remember that Lockheed said it was nothing to do with them, even though there was an obvious difference between an old MC and a new one...

Lost on me, really, Kevin! At least Phyllis stops on demand now!

[Willie]

Gareth...the brakes were supplied by Lockheed as original
equipment so would be preferred choice instead of any
pattern parts. I too do not understand your 'spring
washer' solution. There should ALWAYS be a spurt of
fluid into the master cylinder reservoir when the brake
pedal is depressed, perhaps you had overfilled the level
so that it had no space to go and forced its way out of the
breather hole until you increased the space by adding a
couple of washers????

[Gareth]

The fluid was filled as per the instructions in the manual, so that couldn't have been it. There was indeed a spurt of fluid when the pedal was pressed (looking with the cap off), but when the cap was replaced under most braking the fluid would squirt through the overflow which noticeably reduced the pressure. The Lockheed ones have a baffle inside the cap, I think, which ensures the small hole works as a breather, and not an overflow. Fluid will always find the easiest escape route, and in this case it was through the cap - not a good think, I'm thinking!!

The washers were fitted into the hollow area of the MC cap NOT between the cylinder and the cap. I think that all they do is make it harder for the fluid to spray through the breather, although the level can rise back to normal when the pedal is released.

An original Lockheed master cylinder was compared with a new Lockheed cylinder and on dismantling there were obvious visual differences to the interior of the unit which were, aparrently, concurrent with difficulties in bleed-ing. The Unipart ones were identical to the original Lockheed, so this is what was fitted.

It might have been a bad batch, but there is the possibility that new working practices or machinery has caused slight differences to be built into the new "original" units.

As I've said, I don't know, because I didn't fit it, but it seems to be doing the job, and I don't lose any fluid - before I was having to top it up every 2 days.

[Chris Morley]

Funny how these posts end up going off at a tangent , but all the advice and support has been gratefully received.

Today my saloon 'RHJ' passed the MOT without any faults being found so I celebrated by quickly purchasing a Delphi / Lockheed Master Cylinder. Weather permitting, I'll crack on with fitting it tomorrow once I've read the posts about bending the torsion bar.

One thing - my Autodata manual says you have to disconnect the speedo cable - why? I can't see why this is necessary .

[Kevin]

One thing - my Autodata manual says you have to disconnect the speedo cable - why?

So does the Haynes manual, and the BMC Manual I have but it only goes as far as the 948cc engine
As I have not done a master for such a long time I am sure you will be able to reveal all when the job is underway/completed Chris

[Gareth]

But isn't that on the other side of the car...?

[Cam]

Haynes manuals are really good for telling you do remove / disconnect parts that you don't need to.

I did the CV boot on my Rover and the manual said that I needed to remove the driveshaft. Utter rubbish, just take the hub off and knock the CV off the end of the driveshaft with a rubber/plastic mallet with the driveshaft still in place in the gearbox.

[Willie]

There is absolutely no need to disturb the speedo cable