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MG Midget and Sprite Technical - More Bleeding Brakes

I posted this on the end of Oggers's thread, but maybe you're done with his brakes, so please can you help me with mine?

My new easibleed was waiting for me when we got home yesterday, and today I decided to fill my brand new but empty system and try it out.
Good news:- it fitted and was fluid-tight.
Bad news:- After bleeding I haven't got a pedal.

What's next? Assume lots of air, and go round again? I suppose the way to check if there's something amiss in the master cylinder is to plead with the attractive assistant and see if pedalling moves fluid.
Nick and Cherry Scoop

Yes to both your suggestions. The latter may require a degree of bribery/pleading or both.
Also consider buying a set of Speedbleeders rather than easibleed?
Are you using silicone fluid as a matter of interest?
Jeremy MkIII

I'll start the pleading in about twenty minutes, and hope for something soothing but optimistic on the radio when it wakes us tomorrow.
No - just old Dot 4.
What are speedbleeders?
Nick and Cherry Scoop

A caliper bleed screw that went to college...

Should be readily available

Good luck with the air bubbles !!

Mike P.
Buffalo, NY

Mike Pelone

using a tube on an open nipple into a jar of fluid just keep pumping until the master starts to draw fluid - it will eventually, do a "rough" bleed at all four corners using this method, then revert to the easybleed. I ditched the bottle from the easibleed - means you need to stop to top up the master a few times but far less hassle in my opinion and one less vessel of pressurused brake fluid to worry about when youve got new paint.....
If your system has no leaks you cant really go wrong
S G Macfarlane

Thank you Mike. Nice illustration, and I understood it.
Even with those it's still a two-man operation in the final stages, isn't it? Because you need to see what's going on in the tube, and probably stop the jar from falling over.

Thanks Stuart: I'll try that for a rough bleed, maybe with a heavier jar. You should see the number of rags covering a two-foot radius around the master and the bottle!
Nick and Cherry Scoop

I doubt you have but the PO of mine fit the front calipers on the wrong sides and the bleed nipple was at the bottom so i could never get all the air out swapped them round and perfect no
mark heyworth

What parts have you replaced on your braking system,
Andy Tilney

You can do a one person bleed by gravity or pushing the pedal. You could support the jar with something like a couple of bricks to make it more stable.

This chap pushes the pedal -
Nigel Atkins

Drums on mine, Mark. Everything except the master cylinder and its pistons is new.
Nick and Cherry Scoop

No good. I've made sure all the brakes are adjusted up tight, the handbrake off, and Laura has pedalled while I watch the tube. Only about 6" of fluid movement, which is inadequate, but if there's air being compressed everywhere, perhaps that explains it.

I've now eezibled it twice, at 15lbs pressure, and we've done the two-man method once. No pedal, although it's firm enough to feel like it's moving fluid.
Nick and Cherry Scoop

Is the master cylinder emptying as you pump the pedal?
S G Macfarlane

Have you tried bleeding the master cylinder, which is a good idea if you have had the whole system open, its best to do this first, you need two people to do this,
if you haven't done this before this is how you do it.
top up the master cylinder, pack a load of cloths around and under the M/C outlet pipe so as to be able to catch all the fluid that will come out, don't forget, its only the air you want out not lots of fluid, with an assistant in the car crack open the pipe, with the pipe open push down the pedal down and hold down, lock up the pipe let the pedal up, with the pedal up crack open the pipe push the pedal down, when its down lock up the pipe, and let the pedal up,keep repeating until you just get fluid out and not air, then try your pedal,if the pedal is still not any good,if you haven't got braided flexible pipes clamp them off, and try your pedal, if you get a good pedal, remove the clamps one at a time trying the pedal after each removal,when the pedal goes soft you will know where your problem is,
Andy Tilney

Andy - it's a dual master - looks like this. Do I crack it at the 4-way? I could get a jar under it quite snugly.

I suspect that I've been a bit niggardly with my fluid. It occurs to me that the fluid will be low and the air high, so when I bleed a corner, see bubble-free fluid and shut it off, maybe the air was just about to arrive.

There's always tomorrow.

We'll always have Paris.

Nick and Cherry Scoop

Stuart - yes.
Nick and Cherry Scoop

What you need to do is get any air out of the master cylinder, its usual to bleed as close to the M/C as possible, you could try bleeding lower down on the pipe connections, as long as you lock off after each stroke, it should work, we had lots of different combinations of bleeding brakes/clutches when I was at work,if you don't have any luck with this method I can give you a few more methods we used to use, one of which will sort it,
Andy Tilney

I'll be back to this after dinner today. One thing that occurred to me last evening, while we were listening to folk music in Kington, was that every time I power up the eezibleed the first thing it does is pump a foot and a half of air into the system. Does it stay on top of the fluid in the reservoir?
Nick and Cherry Scoop

Yes it does. All the air does is to add a bit of gentle pressure to the Easibleed bottle, and this in turn pushes fluid from the bottle through into the M/C and the rest of the system. As long as the bottle is at least part full then no extra air gets into the brake lines.

I say gentle pressure as it works best at up to about 20psi. There are stories about the easibleed systems leaking and spraying fluid around the paintwork which maybe result from using too high a pressure. I connect mine to the front tyre but always let a bit of air out first.

Easibleed really only replaces your Attractive Assistant's foot on the pedal. Although there is the other advantage that it provides a steady and continuous one way movement of fluid through the pipes once you open a bleed valve. This unlike the pedal way of doing things which inevitably results in a degree of back and forth flow of brake fluid within the pipes.

The connection from the MC to the 4 way connector is where the air sticks. A nice big loop holding lots of air. Rob
MG Moneypit

I have bled them before by temporarily replacing one of the outlets on the 4-way adaptor with a standard bleed nipple. Not sure that the conical faces are the same angle, but being conical one still gets a good circular line of contact seal. Coupled with sealing off the other 3 routes with hose clamps as Andy says, it works well

I must confess to being a little dispirited.
I tried Guy's method, but I've got those blasted metal braided flexibles, so couldn't shut them off. Got a bit of air out at the 4-way, though.
Been round again with the eezibleed, and thought for about a minute that I'd got some resistance, but if I had, it's gone.

I remember the last time I had to commission a new system, in 2006, somebody - Bob (Robert) I think - said I should open everything and let them all drip together. I will revisit that thread if I can find it, and see what he really said.
Nick and Cherry Scoop

As you were. After a simple and nourishing luncheon I've looked at the 2006 thread. It was Bill (sdgpm) who advocated dripping on all corners. Bob's advice (backed up by Bob) was to pump the pressure up before opening each nipple.

Well, I went out there and pumped the pedal, and I got pressure! That's progress, I do assure you. Got to walk the dog now. Thanks for listening.
Nick and Cherry Scoop

If you have some things of the same thread as on the four way connector you could block off two of the ways whilst using the bleed nipple in the other. Once bleed at that point then connect up the other two one at a time to act the same as squeezing off the flexi-hoses but with a longer run forward on each.
Nigel Atkins

The two rear banjos are weeping very slowly. Does this allow air in? Luckily I did not swap the rear flex for Goodridge, so can clamp it. What with?
Nick and Cherry Scoop

Do you mean weeping from the nipples? Make sure that the weeping is actually a leak. I started another thread a few weeks back (Weeping bleed valve) when I was concerned the bleed nipples were leaking, but they weren't

Graham V

Don't think so, Graham. I had no new copper washers, so I emeried the old ones flat and smooth, and used them. Of course, they had already been compressed at least once, but I didn't think of that at the time.
Nick and Cherry Scoop

Oh sorry, misunderstood. But copper washers I think need to be annealed if used again. Probably easiest to replace for the few pence they cost?
Graham V

No - thanks for mentioning it, Graham. I will cap off the nipples to check that the leak is from the banjo itself.
Nick and Cherry Scoop

After 8 weeks' rest from hydraulics, I'm still in the same boat. Today we returned to the brakes, and tried the aggressive pumping and hold down method. No difference.
Then I pumped up to 20lbs and went round with the Eezibleed. No difference.

Further back in this thread somebody talked about clamping the hoses. What should I use? Mole grips?
Nick and Cherry Scoop

I have used mole grips in the past, although I used a couple of thin strips of aluminium between the hose and the jaws.
Dave O'Neill 2

Ditto, but with a folded strip cut from a milk container to protect the hose from the mole grip jaws.

Nick buy yourself 3 brake pipe clamps, they are cheaper to buy than a dozen tins of brake fluid, if you were stuck in the desert or in the middle of the jungle, yes you could use mole grips, but these are worth there weight in gold, they are one of the most versatile bits of kit you can own, when ever I go on a European tour in my car these are the first thing I pack,you can do so many things with them, and as for brake problem diagnosis, they are invaluable.

Andy Tilney

Look, I'm so fed up with this - which should have worked by now - that I've opened up the master cylinder to make sure all's well. As usual, I don't understand it, so can someone tell me how it works? This is what I found; I've concentrated on the rubber bits, which do the pushing.

What are the pitfalls? And - how does new fluid find its way into the system??

Sorry about the drawing: not one of my best.

Nick and Cherry Scoop


When I have had stubborn bleed situations I sometimes found relief by bleeding the master by cracking the lines from the master, and then continuing the bleed at the wheels if necessary. Of course with it on the car you would have to do something to prevent spilled fluid from eating your paint.

C R Huff

Thank you, Charley. That will be difficult now.

The two things I don't get are:- (1) when the piston moves up the cylinder, how does the fluid get past #6? and (2) how does the fluid btween the two cups get past #5 to replenish the system?
Nick and Cherry Scoop

Partial answer: on the return stroke the seal at 6 (which is slightly tapered) collapses inwards and allows fluid past the outer edge.
David Smith

Thanks David. Actually, there are 4 holes in the metal body of that valve at #6, not 2. I was drawing from memory, and in a temper.
Presumably the function of that valve is to open when you brake, close while the brakes are on, and open again on the return stroke to release the brakes.

Sources I've looked at show different valves at #6. But here's a picture from when I opened the mc on my MkII all those years ago. Something utterly different on the right.

Nick and Cherry Scoop

BTW, thanks Andy. Those clamps look ideal: firm but gentle.
Thanks also Dave and Guy for those precautions.
Nick and Cherry Scoop

Did the Mk2 have discs or drums?
Dave O'Neill 2

(5) will seal only in one direction by design. When the chamber on the left in your sketch is at atmospheric pressure during the return stroke (or even slightly negative owing to the spring) fluid will readily pass the inward facing lip.
On the pressure stroke the lip is held tightly to the bore to force fluid past (6) by collapsing the rubber within the steel cup. The steel cup is not sealed to the end of the bore and doesn't need to be, since the cylinder pressure should always be equal to the line pressure to the brake. On the return stroke fluid simply re-enters the bore around the cup.

At least that's how I see it.

Grey's right - and re-reading my post I meant 5 not 6. Sorry if I only added to the confusion!!!
David Smith

Ah that explains it David. I confess I was slightly lost with your earlier post but it makes perfect sense now.

Thinking now about Nick's problem of not being able to get a firm pedal.

I presume that somewhere there is a bubble of air trapped in the pipework such that the volume of fluid shifted forwards as the piston seal (5) moves forward, is insufficient to move the bubble forward towards the nearest bleed nipple. Or more exactly, the bubble moves forward in the pipework but is then sucked back to its start position as the piston moves back to its "at rest" position.

This suggests to me that there is something preventing, or at least limiting fluid from getting past the seal (5) to maintain the fluid on yon side of the cup seal. Greybeard is right in saying fluid will readily go past the lip of the cup on the return stroke, but it also needs to flow through the ring of little holes in the crown of the piston, and past the washer.

Now I know that the crown of the piston is domed; is the washer also domed or is it flat? If its domed, and put in to lie flat against the piston crown then it might effectively seal those little holes. Then, when the pedal is released and the cup and piston move back, instead of allowing fluid to cross freely to the front side of the cup, it would be strangled and the piston instead would exert suction on the fluid, pulling that vagrant bubble back into the depths of the pipework.

Theorising, of course!

The most likely place for a bubble is as shown in your modified sketch. It can be difficult to shift but unless you can get rid of it you will not be able to bleed the brakes.

I've had situations where the stroke is enough to compress the bubble and let fluid past. Then when you release the peddle the bubble expands again and you never get a good peddle feel.


MG Moneypit

The easibleed should provide a gentle (20psi) continuous pressure so that the fluid movement isn't limited by the stroke of the peddle, but is continuous.

Limit the routes to exit to just one by compressing selected hoses. If necessary, do all three and bleed out air by cracking open one of the pipe connectors at the 4 way junction.

Thank you all for your help. I understand how it works now - though it's difficult to imagine that rubber cup at #6 collapsing inwards.
I escaped from it today by going out for the afternoon, but the master cylinder's back together now, and I filled as I went, getting fluid in as soon as the primary cup was in the bore, but there's little doubt that the bit of pipe Rob points to will be full of air. Guy, the wavy washer goes the way shown in the drawing, so should leave the holes free. Dave, on the MkII I changed the fronts to discs.

Tomorrow I will try the easy method first (eezibleed), and go on from there.
It may work: after all, I have attempted a classic solution - turning it off and on again.
Nick and Cherry Scoop

Looking at the sketch Rob re-posted you could maybe replace the pipe connector with a 3 way and install a bleed nipple at the high point, with the pipe connection at the side instead of on top. That would serve to purge the m/c before moving on to the rest of the system.

I'm nearly certain I've seen something of the kind somewhere but I disremember where or when.

(Like so much else, sigh...)

I've been thinking about your idea, Grey, and it seemed to me that I should first get the brake pipe loop as low as I could. So I've done that - carefully - and it's now just below the filler cap neck. If I fill to the top, I will have a head of fluid!
Nick and Cherry Scoop

After a long and painful series of failures (still ongoing), I came across this illustration in my workshop manual.

Should I have item 7? It didn't appear in the repair kit I got from Moss.

Nick and Cherry Scoop

Nick, have you read up on the Gerard's Garage notes?

And this one:

It is important to use the correct components (7,8and9) when using disc brakes with these single unit master cylinders.

Very interesting, Guy, despite the second chap's ludicrous contempt for drum brakes. But I'm sticking with drums, and I'm perplexed. Haynes makes no mention of the rubber washer at the end of the bore, but the workshop manual actually says, " Place the rubber washer (7) in position in the bottom of the cylinder bore. Fit the rubber cup (8) in the valve body (9) and assemble the body on the larger end of the return spring (10)."

This manual makes absolutely no reference to disc brakes, as far as I can see. As it happens I have an old repair kit for an MGA, which has the rubber washer in it.
Nick and Cherry Scoop

Sorry Nick. I thought you had converted to discs, in which case there may have been something of relevance there.

From what l understand, correctly adjusted drum front brakes are perfectly good, and as powerful as discs. Where discs do have the advantage is in being self adjusting, and l think less prone to fade.

Is there a frogeye owner out there, with drum brakes, who is intimate with the contents of the master cylinder? I would really like to know whether the Workshop Manual is correct about the need for a rubber washer at the bottom end of the bore.
Nick and Cherry Scoop

Guy wrote:

"From what l understand, correctly adjusted drum front brakes are perfectly good, and as powerful as discs. Where discs do have the advantage is in being self adjusting, and l think less prone to fade."

This has always been my understanding also. In fact I think that (disregarding servoes) drum brakes are more powerful than early types of disc brakes owing to the greater contact areas.

Many types of drum brakes are also self-adjusting (har-har, yeah right. Good luck with that 😅) but yes they are more fade-prone because they cool less effectively.

They're also more slip-prone because they retain water if they get proper wet, unlike disc pads which dry pretty quickly from the residual heat in the assembly. Who else remembers the weird public information film in the 60s about braking after wading through a ford to dry the brake drums and shoes? Chap with brylcreem hair and a pipe and the happy family smiling sweetly. Happy days!

What can this rubber washer do?
1. It cannot affect the train of cups, or their positions in the bore.
2. It does not affect the holes in the roof of the bore.
3. It will compress the spring a little more.
4. It may make a better seal at the open end of the valve cup, where before it bore against the metal end of the cylinder.

Grey, having had discs on a MkII, I believe drums are sharper, and require less leg to brake well. On the other hand, I remember a long and steep descent into Lyme Regis, when I used the brakes instead of experiencing the authentic sixties low gear method, where the brakes disappeared completely.
Nick and Cherry Scoop

I wouldn't swap back to drums from discs. I recall many years ago driving down the A20 towards Brands Hatch in company with 2 other frogeye's We were cracking along along at a good old rate when something from the truck in front blew off. I had just fitted discs from a midget but the other frogs had drums. I was able to slow and swerve and miss the debris but the other two despite fairly frantic attempts were less successful!!
Bob Beaumont

This thread was discussed between 25/04/2018 and 04/07/2018

MG Midget and Sprite Technical index

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