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MG MGB Technical - replacing clutch hydraulics

I've finished stripping the hydraulics from my garage find and am about to replace the clutch hydraulics(master cylinder, copper pipe, flexible pipe, slave cylinder). Are there any precautions I need to take with the pipe connections? I haven't dealt with hydraulics before. How tight to do up the copper pipe connections? Should I replace the copper washers at the master cylinder banjo and slave cylinder connections? Can I bend the copper pipe by hand or do I need a special tool?

It appears that the PO had used PTFE tape on the threads of the copper pipe unions. Is this really necessary?
Steve Church

The connections should seal with just 'normal' tightening, and they shouldn't need any PTFE or other sealant. Neither should you need to replace the copper washers, even if you didn't get a new one with the slave hose (some brands do, some don't it seems). I've replaced various brake and clutch components on several cars in this way without subsequent leaks, just make sure the joining faces are clean. You may well need a pipe bender or you could flatten it, unless you are careful to work along the metal pipe bit by bit bending bit by bit.

Fit the slave to the bell-housing, screw the flex hose into that, then offer the other end up through the chassis bracket, fit its securing nut and washer, then screw the flare nut at the end of the metal pipe onto the end of the flex hose. If you tighten the metal pipe end before screwing the other end into the slave, and/or the slave isn't bolted to the bell-housing the chances are that the flex hose will end up twisted which is a Bad Thing.
PaulH Solihull

I think hydraulic fluid turns PTFE to Goo.
c cummins

If you're not replacing the copper washers, it helps to anneal them. Heat them with a propane torch and let them cool naturally. This will allow the metal to return to its original shape and provide a better seal. RAY
rjm RAY

You only use PTFE tape or goo on tapered pipe thread joints. These joints are not that type.
Art Pearse

I've just completed a trial fit of brake and clutch pipes so here's what I learned.
If you have the old copper pipe, trial fit it with the master cylinder in place to see if it runs the way you want. Then measure its length with a piece of string to compare it with the new pipe. If they are the same you can reliably bend the new one using the old one as a former. If of a different length you will need to see where you can 'save' length or 'lose' length. In these cases I would recommend making a former from some stiff wire cut to the string length. This will get the new pipe to a very good approximate shape.
I found the pipe relatively easy to bend by hand for large radius curves but used a pipe bender for the tight corners (about 4cm radius) to ensure it didn't flatten.
Richard Coombs

Umm. I don't have a pipe bender. Are they readily available?
Steve Church

I got mine from Machine Mart (CHT264), about £13.
Richard Coombs

Steve,
There is an old mechanic's trick which you may want to try.
Stand a broomstick or similar upright in the vyce and bend the tube around it by gently sliding it from side to side while applying pressure.
This acts in the same way as a tube bender and will allow you to make quite tight bends in both copper and steel tubing without flattening.
I made all my brake and clutch lines using this method - it is surprisingly simple and effective.

Regards,
David
David Overington

A tube bender works by bending the tube inside two U-channels. I'm not saying the broom-handle doesn't work but it doesn't have those channels and I can't see much difference to bending manually. Personally without a pipe-bender I'd put the pipe between the vice jaws, lightly clamped, and bend the two ends upwards (or downwards), the jaws resisting the tendency for the sides to bulge out which is what happens when it flattens.
PaulH Solihull

Well, what can I say except that I was able to make a complete set of steel hydraulic lines for my Magnette, (brake, clutch and booster), by using this method with no flattening problems. The method was shown to me by a British car expert with 40+ years experience.

My comment about the similarity to a tube bender was a bit simplistic, I know. I meant that the bending force was spread across the inside radius in a sliding movement.
David Overington

Steve, this is how it can look if you get the curves in the right place.


Richard Coombs

Another view.


Richard Coombs

Make sure the hose goes into the END of the slave cyl NOT the side as I have seen all too often. When bleeding it is hard to get the air out of the top of the pipe by the master cyl unless you use pressure & feed from a suplementary bottle to get a good supply. Another way is to pump frantically 30 or 40 times, wait a whilst for the air to go out of the fluid & repeat as often as necessary till you get a good pedal.
Garth Bagnall

The couple of times I've done it has been by reverse bleeding, first with an Eezi-Bleed on very low pressure, then following someone else's suggestion by using the right caliper. The two bleed nipples are the same size, have someone apply slight pressure to the brake pedal when opening that nipple, and only use slow and gentle pressure. Just a couple of pumps had fluid visible in the clutch master to be topped off as normal, with very little reduction in the brake master. This is *despite* reverse bleeding meaning that air has to flow out of the *lower* hole in the slave, the bleed nipple being at the highest point.
PaulH Solihull

This thread was discussed between 04/08/2010 and 08/08/2010

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