“Here we go again” 1275GT project NOW FOR SALE

[Peter Laidler]

I'm just about to embark on making new C post trims for mine so am following this part with interest. Looks like plasticard is the way to go. Q for Andy first. Why use 2mm (2x 1mm glued together) instead of 1mm. I'm certainly going to heat up and form to shape first. I'll be making new/replacement Mk2 trims from a couple of wider Mk1's

[Dearg1275]

Some you win, some you loose. Some of you may have noticed that I like to conserve as much of I can when restoring my cars. This extends to master cylinders. A pair of originals arrived with this project. Starting with the clutch slave this checked out and the bore honed up fine and coupled up to the untouched master it worked fine and the clutch master showed no sign of leaks even under heavy pressure.

So far so good. Next up, check the master bore and seals and plunger. These were in cracking condition and once reassembled still held pressure with zero leaks.

Now to the aesthetics. The plan - blast clean and re-plate.

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But the “best laid plans” and all that.

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One of those perforations is frighteningly low and could have been very nasty had it become patent whilst in use.

So now the only question is - which should you check out first the bore or the can. This episode says to me that giving the can a rub over with a wire brush and a lick of paint is just not a wise move. Of course corrosion can also progress, unseen, from the inside outwards. Sobering thought.

D

[Andrew1967]

Had exactly the same issue when doing the refurb on the Mk2 Cooper. Had some spare brake masters and the bores weren’t great.

The two with good bores ended up like yours after blasting BUT one was only holed on top with two small holes so I soldered them up.

[mini_surfari]

How do you go about pressure testing them at home? Got a few I’d like to refurb!

[Peter Laidler]

If you had a few bits of steel and a long handle - and a high pressure gauge you could make a simple pressure tester for the inner pressurised part Oli. You could make a simple adaptor to put a bit of pressure into the fluid container if you were unsure about its integrity by using a bike tyre pump and a valve in an old filler cap. Much as the old apprentice VM's used to do by using an old rad cap by fitting in a tyre valve to make a radiator pressure tester

But I'm trying to think of a sensible way around Deargs and Andy 1967's corroded tanks. I'm thinking that while good used, repro and NOS master cylinders are available, there'll be a day when they're not. So it'll be a case of make and mend. I'm still thinking..........

[roger mcnab]

hi d
just looking at the object in question could one be repaired with a couple of jam tins or such and solder it all together a bit of a fiddle but anything is possible with a bit of effort
just a thought maybe a crazy one who knows
cheers roger mcnab

[Dearg1275]

How do you go about pressure testing them at home? Got a few I’d like to refurb!

I am not trying to work out what pressure is developed only if there is a leaking seal. This is my set up/ lash up.

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The bar gives a 10 to 1 lever ratio and the bucket holds 10litres of water =10 kg. The cylinder push rod therefore sees a force of approximately 100 Newton.

The spirit level is set level once the bucket has stop swinging. If the level has moved when inspected later (half an hour seems reasonable) then it is by my reckoning leaking.

The radius of the bore is 0.35 cm = 0.0035 m. Thus the cross sectional area in meters is 0.0000385sq m. This means the pressure is 2.6 mega pascals or in Imperial 377psi.

I think this is a reasonable test pressure. Any leakage past the bottom seal will spot on the paper towel.

Yes a lash up but easily constructed even if you don’t have a spare pedal box.

D

[GraemeC]

That's a nice simple test rig - good thinking.

[mini_surfari]

Brilliant, makes perfect sense, will give this a crack!

Thanks for that!

[Peter Laidler]

Brilliant..... Where there's a will, there's a simple way. I like this thread.

but back to the conundrum at the top of the page. Given that the 'can' or reservoir part of the master cyl is sweated/soldered to the main pressure bearing actuating cylinder I wonder if anyone had ever considered simply 're-canning' an otherwise perfect master cylinder, by using the can from a corroded cylinder.. It's really no different to re-sleeving corroded cylinder.......

[Dearg1275]

That’s the easy bit done. Good bore bad can clutch master.

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I had hoped the heat would travel enough from one end hence the blueing. In the end a good
hot flame to each end alternately was all that’s needed. As you see the threaded neck is also soldered on so some care will be needed to isolate the heat when disassembling the donor can.

I have a small can repro brake master that has donated its innards to a large can brake master (as in the test rig above). The can is now available to donate to this now bare cylinder. Low on gas though and I need to sort the right solder. Thick lumps of body solder will just be unmanageable but the tinning paste may be useful.

D

[Andrew1967]

Be interesting to hear how this goes David.

Test rig is a great idea

[Tim]

I've changed cans over before. I fitted a decent can off a later model M/C to the earlier 'hexagon top' cylinder on my '61 Traveller. The hardest part is getting enough heat into the cylinder without getting too much into the can.

I originally disassembled them when I had them re-sleeved in stainless. The re-sleeving guy would have either done it himself, or drilled right through the can, but as the can was pinholed already it was easier to just take them apart. I had clutch and brake done at the same time.

I used a liquid solder paste that includes the flux, to get it back together.

The other thing you can do, and its easier than completely replacing the can, is to unsolder it and rotate it around the cylinder. Sometimes with engine or vehicle mods the can is in the wrong location, or obstructs something. Just heat it up and turn it.

Tim

[Peter Laidler]

You're both braver men than me David and Tim....... Thinking about how you go ahead now David..., you've done the difficult buit. A bit of what Tim from Tassie has done (above) and a good heat sink and you're home and dry. That's said, standing on the side lines looking with admiration. Great thread.

Out of interests sake, did you ever consider a simple tinned patch over the pin pricks? Or too unsightly?

[Dearg1275]

Seemed a shame to split the repro master but.. The attempt to contain the heat with a damp towel worked too well. I couldn’t heat one end without the other cooling too fast.

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I tried modern plumbers solder on the base but it needed a lot of heat to flow well. Short bursts of intense flame got a reasonable result.

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The upper joint I carved some ribbons of body solder and laid these in a ring around the cylinder. These melted into place much quicker and more smoothly.

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The worry is that the soldering of the top and more importantly the base of the can may have suffered. Time to blast it all clean and test the can for leaks.

D

[Dearg1275]

Now blasted and filled with fluid. Fluid shows up nicely on blasted metal so now was a good time to check. No leaks. I even got the can facing the right way.

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D

[Dearg1275]

Job done,

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D

[Rubber Sprung]

You can get lead free solder or solder with lead still ,the one with lead melts at lower temperature and flows better you will find .

[Dearg1275]

You can get lead free solder or solder with lead still ,the one with lead melts at lower temperature and flows better you will find .

I was using what I had to hand. The lead free, used on the lower joint, did take much more heat to melt and flow. The body solder used on the upper end flowed in seconds.

D

[Dearg1275]

It was time to find out what horrors were hidden in the gearbox today. No detailed inspection yet but this box has had the usual ‘70s care. Zero! Mountains of sludge in the bottom and frankly grit (it doesn’t even look metallic). The engine has been off the top of it but the box itself doesn’t appeared to have ever been touched. The maintenance has been the usual pretty coats of paint that were typical of the ‘70s.

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It looks better internally after it’s initial clean down with diesel. No fractures found so far and the bearings were tight in their housings so fingers crossed - a good case.

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D