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MG MGA - Master Cylinder Blow Out

I have just increased the MPG for my current tankload of fuel by being towed 5 miles after a catastrophic loss of fluid from the master cylinder. It happened over a period of approximately 4 gear changes and braking and very nearly ended up with an accident. I was then unable to engage a gear from stationary. I probably had a bit of braking capability left but the pedal was feeling very spongy, so I used the handbrake during the tow and kept the last brake push for emergency.

An initial look shows the bulkhead flooded in fluid - thank goodness it's silicone fluid. First problem I have had with the brakes and clutch in 9 years.

I phoned up Bob West. He said such a failure is most rare, but is unlikely to be the seals, more likely a failure associated with a banjo union at the back. I will have a deeper look at it over the weekend.

Anyone want to lay bets on the cause before I reveal all?


Steve
Steve Gyles

Very nasty - bad luck Steve - or should I say good luck that you didn't hit anything . Let us know what the fault was -cheers Cam
Cam Cunningham

I don't think the problem is that rare as someone else posted a similar problem about a year ago.

Though purists may want to avoid this conversion, two individual circuits is the only cure for this potential problem.

If anyone wants details let me know. jmbries@yahoo.com
JohnB

The problem is fairly common. As John stated, many of us have updated to the B master for safety reasons.

Good luck!
skip

It was the copper washers on the clutch banjo joint. I am surprised how quickly the whole system failed with so little warning. I can see where John and Skip are coming from. I would not wish this type of failure on anyone. I was intending going on a 400 mile round trip in the car today. I had prepped the car and was not going to use it yesterday. Had I stuck to my original plan the failure would have occured on the M6 motorway.

Steve
Steve Gyles

To quote that famous movie: "Houston, we have a problem".

Just been draining residual fluid from the MC, sucking on a clear plastic tube, and out came considerable globules of black sludge. The bottom end of the tube was also covered in it. Is this the seals on the way out?

Steve
Steve Gyles

Steve

When my seals started giving out, it was an inability to hold pressure on the clutch side that gave the clue, and there was no sludge when I stripped down. The seals *looked* OK, and in fact one was temporarily pressed back into service because of an out-of-spec issue with the new kit. As you know (from recent discussions) I am anyway a bit of a fanatic about brake parts!

I suspect that the washer has been re-used and not annealed before re-use? Is it cracked?

I also look after a very early B, and when first acquired found that it had problems with brake system pressure. Bleeding temprarily resolved the issue, but pedal pressure started getting soft after a few days again. That too turned out to be a copper washer problem at the back of the MC, and it was MUCH harder to get to than the ones on the A (though I know that is hard to believe!) The benefit is at least that on the B the systems don't share the reservoir.
dominic clancy

Dominic

First inspection suggests the seals may be ok. A picture of the sludge held in suspension of the silicone fluid is at: http://freespace.virgin.net/stephen.gyles/odds_and_sods.htm

I have been speaking with James at Bob West's work. They have seen this a number of times with silicone fluid about 9 years or more old. Fortunately it does not always produce problems unless some of the sludge blocks the pressure relief hole.

Interestingly, the cause of my problem was failure of fibre washers in the clutch banjo union. How they got there must be down to me 9 years ago. They should be copper washers!

I have now had 2 banjo unions leak badly within a short time of each other. I wonder if the prolongued UK heat wave (expansion etc) has any bearing on it.

Steve
Steve Gyles

Steve

I have also seen fibre washers used where copper ones are specified, and hopefully your reports are not causing too many people to regret that particular short-cut in their hydraulics. I have to say that I have never had banjo unions start to leak unless something has disturbed them, and we do get pretty high temperatures here in the summer, and I also use my car a lot in the winter when it's below freezing.

I use copper washers wherever I have to seal an oil or hydraulic joint, and also under the various manifold fasteners for the Supercharger (to prevent any air leaks, which make the thing uncontrollable).

The silicon sludge is a bit of a puzzler - which brand do you use? It would seem to suggest that an occasional purge would also be in order.
dominic clancy

Steve

Glad you are and the motor are in one piece. Yes fibre washers are not the preferred option here! As I'm sure you appreciate, copper washers get work-hardened after tightening. For the record if you ever re-use copper washers, heat them to red heat (on the gas stove) and quench in cold water to soften them. Give them a clean up with some fine emery to knock off any muck and you have a new washer again!

Happy motoring!

Pete
Pete Tipping

The silicone fluid I have is Automec.

Whilst not wishing to sound alarmist, one of the fibre washers was very sticky and began to disintegrate as I separated it from the banjo. I would now strongly recommend that fibre washers are never used with this banjo.

I have also re-examined the sludge. The dark green stuff in the link I posted seems harmless enough. It is much the same viscosity as the silicone fluid. But in another container I have black sludge that I sucked out initially with a pipe. This has small black bits in it. However, the seals look in A1 condition. Nevertheless, I will be changing them.

Steve
Steve Gyles

Hi Steve, I have been running silicone brake fluid in my vehicle for almost 20 years. When I started rebuilding my hydraulic system this year, I found much the same black sludge in my system, and particularly the master cylinder. On close inspection, it appears that the black sludge is composed of microscopic particles of rubber, probably from slowly disintigrating seals. I stripped the hydraulic system completely and have installed all new components including copper nickel pipes, new hoses, rebuilt cylinders, calipers, and master cylinder. It has been so hot here in Ontario Canada, that I have been unable to finish the job by bleeding the brakes. Hopefully we will get a cool spell, so I can get my baby back on the road. Cheers, Glenn
Glenn

Glenn,
What affect does heat have on the brake bleeding process????
Tysen

I've been warning about the single brake system for years. I had a near fatal crash when a rear wheel cyl blew a seal years ago and the brake pedal went to the floor in a split second. And let me tell you that when it happens, the distance from brain to hand to emergency brake is a long way.

That's why I always get a kick when folks on this bbs go on about not taking chances with a rebuilt ms. The fact is that a single system is just begging for the worst kind of failure you can experience.

Skip, can you send me a pic of your B system? Do you use the 68 - 74 non-servo unit with the pressure failure switch? I'm especially curious about the bracket set-up, is it mga or mgb?

My soultion on my driver was to use 3 wilwood cyls, but I had to remove the heater box and wiper motor. I want a better arrangement for my resto project.

Glen, I was almost convinced to go with silicone fluid, now I'm having second thoughts again. I don't remember, before you just put in a new system, had you just cleaned the system and added silicone fluid?
Fred H

Fred

I am inclining to your way of thinking also. As you say, when it goes, it goes fast. It went from fully functional to total failure in 300 yards. Perhaps Skip and others can post their split systems for us all to see.

In the meantime I will be the putting dual system back in with all new bits, copper washers and fresh fluid.

Steve
Steve Gyles

Hi Tysen. I have some serious medical problems that prevent me from overexerting, especially in the heat. When I was younger, the heat didn't prohibit my working. Unfortunately, it does now. Cheers, Glenn
Glenn

Hi Fred. back in the early 80's I learned about silicone brake fluid. The instructions with the fluid said to simply drain the old brake fluid, and then refill the system with silicone fluid, then bleed. I Followed the instructions, and NEVER touched the hydraulic system for over 20 years! Not so much as a hose or seal was changed in all that time! Pads and shoes were changed several times. The braking system worked flawlessly for all that time, and I believe indicates that Silicone fluid is highly superior to most if not all regular brake fluids. I'm quite sure that if I had have used regular fluid, that my hydraulic system would not have lasted a quarter as long as it did. Silicone fluid preserves rubber seals, has a high boiling point (500 degrees F), does not absorb water, and does not eat paint. In mho, Silicone fluid is the ONLY way to go, unless an enthusiast has extremely special requirements, for example campaigning a race car. Cheers, Glenn
Glenn

Steve, what do you mean, "putting dual system back in"?
Fred H

Fred

I was referring to the standard MGA master cylinder with the commion reservoir for clutch and brakes.


Glenn

I am and always have been very pro silicone fluid. My entire system was absolutely brand new 9 years ago so no fears of contamination with other fluids. I was most astonished when I syphoned out these dregs from the bottom of the reservoir, hence my comments earlier and link to the picture. I have now filtered all the fluid through white gauze and will post the picture on the same link above in the next half hour. Most worrying.

Steve
Steve Gyles

Glenn I understand now I thought the heat had an effect on the bleeding process itself.
Tysen

Hi Steve I think the truth is finally coming out about the Le mans incident!!

Terry
Terry Drinkwater

Terry

You mean your master cylinder was on the way out also!

Steve
Steve Gyles

Steve,
I have enjoyed you posts and I am very glad there was not worse consequence for you. Sorry about your cancelled trip, hope the repair goes well.

Your experience of course gives us all pause, especially those of us with single system hydraulics. Along with others I would like input from others on the fix with the best effectivness, least intrusion and least work.

On the other issue, I ran silicone fluid for probably 15 years or so without problem. During my recent rebuild, my shop, Britalia in Fullerton, convinced me I would be better off with standard Castrol GT LMA fluid. I wish I could remember their argument for it. I have no dog in the fight but I wonder if a) the failure and b) the sludge would have occurred with standard fluid?
Steve
Steve Meline

I believe I have discovered the source of much of the hard debris in the sludge at the bottom of my master cylinder. I have been examining all the components under strong magnification.

Referring to the hydraulic system in section M of the MGA workshop manual, the inner edge of the washer - primary clip to piston (No.31) on the clutch side has worn/cut/ripped a deep circular groove in the face of the Cup - secondary - piston (No.30). Much of the debris is the right size to have come from this groove. Examination of the washer shows a very rough inside edge on one side where slivers of metal have flaked off. I found debris consistent with this flaking.

The brake side of the MC shows a circular mark on the cup but no gouging.

This was a brand new Lockheed Master Cylinder, unopened by myself, so any wear is the result of original parts manufacture and assembly.

I will post a picture later on tonight if anyone is interested.

Steve
Steve Gyles

Steve, You just mentioned something that may be a clue: "brand new Lockheed Master Cylinder, unopened by myself". The source of the sludge may be the assembly grease used by the mfgr. I seem to recall that it may have been green. Could you be seeing the remnants of this, disolved over the years by the silicone BF and then precipitated to the bottom of the M/C?

Chuck
Chuck Schaefer

I am thinking of buying new parts from SC parts in England and having them sent over Fed ex . I am wondering if this is a viable / cost wise decision ?? And/or now maybe I should convert to a MGB set up ? any thoughts on sending 60 coupe hydraulics bought from SC Parts across or converting to mgb for resto/safety puposes ? Safety over originality No Problem . Thanks Karl
karl

As a SCUBA diver I have been using Silicone mask for decades. The mask is still clear but it is a discolored clear due to storage contact with black rubber. While I realize that my mask is hard silicone rubber and silicone fluid is not, I believe that the discoloration is due to that. Also, most probably the wear noted by Glenn is the cause of the sludge, while the black rubber is the cause of the discoloration. Now, why don't they make silicone or urethane rubber brake parts? Would this be wise, or not?
mike parker

I think that there are a lot of safety features that don't distract from the car. If someone claims your car is not restored as a result then it is those who have a problem you are simply being sensible.
The dual line brake system is a very good one as are seat belts!
Bob (robert) I am turning? yes I once owned an MGWasp!!

Skip

It is certainly a thought. I am not a chemist so I have no idea whether assembly grease would be held in suspension in silicone fluid, but perhaps disolve in standard fluid. I cannot remember from 9 years ago whether I rinsed through the inside of the MC after unpacking and installing. I suspect not.

I have posted some pictures of the damage to the cup seal and flaking to the washer. Interestingly, to me at least, the flaking and roughness to the washer was on one side only, the other side was machined perfectly flat.

http://freespace.virgin.net/stephen.gyles/odds_and_sods.htm

Steve
Steve Gyles

I meant Chuck, not Skip. Sorry to confuse.

Steve
Steve Gyles

Stgeve, No offence taken. I've been called worse before and probably will be again:>)

Chuck

Chuck Schaefer

That was not done intentionally, I meant to type "Steve".

Sorry,
Chuck
Chuck Schaefer

You guys are a hoot....

I will get photos as soon as my car arrives back in town. The B set-up we use is on our MGA vintage race cars. Its all B components but still use the A foot box. Still really the best way to go is as Fred states, 3 master Wilwood or Girling as I believe the Delux and Twikies have. Vintage rules here on the west coast are very rigid so the 3 master option is pretty much not an option. (although some of you have) ahem! www.vintage31.com
skip

Skip

I like the 'D-Type Jaguar' look on your MGA race cars. Suits the MGA profile.

Steve
Steve Gyles

Thank you for your kind words Steve! When I decided what color to paint the cars I knew to go with Jag colors. The 31 car is a Jaguar BRG - 60s and the 41 car is a D-type Jag color. I've alwasy loved the simplicty of the Jags graphics and the blank white dot on the rear of the cars. I've searched but to no avail why the dots were blank. Any Jag historians out there?

To finish first one must first finish.
skip

I recently purchased an original Lockheed Master Cylinder reservoir level switch with light for my MGA. Although the car isn't ready yet, I do plan to install it. Has anybody had experience with this, and has it helped?
mike parker

Mike

Such a switch would have helped me. Where do you plan to install the warning light?

Steve
Steve Gyles

You mean the big dot where you put the number?
Tom

Steve.
I don't know yet. I think it will be an add on bracket below the dash, but I may change my mind on that.
mike parker

Steve

Appreciate all that has been said, but initially you said...

"It happened over a period of approximately 4 gear changes and braking and very nearly ended up with an accident."

Nobody seems to have addressed this. Are you saying here that the MC went from full to empty in 4 gear changes?

My feeling is that the level had, unknown to you, been rapidly dropping unchecked. During this time everything would have appeared OK until the level hit bottom. The last time you lifted the clutch/brake pedal air would have drawn into the cylinder(s) waiting for the failure to happen.

I wonder - how long before the failure did you last check the fluid level? I reckon regular checking can detect these little leaks and you can see what's going on in them pipes.

Have you got the 1500 MC or the larger reservoir 1600 type? Just interested - there but for the grace of himself, etc...

Pete
Pete Tipping

Tom - Jags ran a white dot on the back of their cars with no number within the dot. Numbers were only in dots on the front and sides of the cars. Any ideas why?
skip

Super Sleuth Peter

Well asked. Coincidently, I had actually checked it the night before and it was full. Nor were there any signs of fluid on the shelf. When it happened the shelf was awash with fluid and also a puddle had formed in the road where I came to a stop. Granted the fluid level may have been dropping during the first 3 miles of my journey without me knowing and it was only when the system was almost exhausted that I felt it going - the last few hundred yards.

I have the original 1500-sized reservoir. It has been adequate til now. I had previously been advised that the smaller reservoir would be ok with the disc brakes I had fitted on the front provided I kept the reservoir full, hence my regular checks. A larger reservoir would just have given me a larger area of shelf to clean up!

Steve

Steve Gyles

Hi Steve

MG never considered the outcome when the clutch hydraulic system failed, more modern systems that share the same resevior, have the clutch outlet pipe set at a higher level so that the resevior cannot be emptied by a clutch fluid leak, and the braking system is unaffected. I don't think that the MGA cylinder could be modified successfully, seperate cylinders a la Twin Cam is a possibility. As you mentioned, fibre washers should not have been used.


Regards

Terry


Terry Drinkwater

Terry, I can imagine brazing (or mig welding) a divider inside the M/C to form separate clutch and brake reservoirs. But modifying the M/C in this manner only protects the brakes if the clutch slave fails. The likelyhood that the wheel cylinder fails is 4x more likely, since there are 4 more of them.

Chuck

Chuck Schaefer

Mike

Where did you find the Lockheed Master Cylinder reservoir level switch to fit an MGA? E Type Jags have reservoir caps with float switches but I have never seen one to fit the MGA.

Thanks

Larry
58A
71 S III E-Type
Larry Hallanger

I now have the correct set of copper washers. Is it just sufficient to ensure that all mating surfaces are perfectly clean before assembling and tightening or should a gasket glue also be used? Expert advice please. I am not taking any chances this time round.

Thanks

Steve
Steve Gyles

Steve, I would just make sure everything is very clean, no burrs, and assemble without any sealant/gasket adhesive. Also, you say "correct set of copper washers". Are they NEW copper washers?

George
G Goeppner

I do not fully understand how the reservoir could be completely emptied by a leak in the clutch pipe. I believe the master cylinder in my Mk I midget is identical to the one in the MGA, and am pretty sure there IS a divider in this. Low down, yes, but it is there.

Tore
Tore

Just a guess but the black sludge may just be material wearing off the rubber parts during use. Since systems with silicone fluid seem to operate for years without problems it may just build up over time. If you were running standard brake fluid you would likely have had the system apart more often for service, resulting in more frequent cleanings.
John H

George

Many thanks. Yes, brand new from Bob West.


Tore

I understand exactly where you are coming from. There is a wall 17mm high. My foot went most of the way to the floor when stopping and was very spongy. I can only suppose that the remaining 'reserve' on the brake side is barely sufficient for that needed to apply 2 drum brakes and 2 disc brakes and that what there was had got aerated in the last few hundred yards of clutch pedal operations.

Steve
Steve Gyles

Steve

I agree with Torre, with the foot off the pedal the brake cylinder is fully primed and does not require any more fluid. The dividing wall should have retained sufficient fluid in the brake half of the reservoir for any small adjustments in volume. HOWEVER I do know that the raised top to the master cylinder was introduced for disc brakes because of the greater fluid demand when compared with brake shoe cylinders, but the the pistons within the calipers for disc brakes hadly move at all when operated and cannot give rise to much fluid change of level in the reservoir.

John
J H Cole

John

I agree with both you and Torre. However, practice did not validate the theory. I can assure you that braking was very greatly impaired. It certainly worried my for a while on what was quite a busy road. I actually overshot red traffic lights by a length and a half. Fortunately the car in front went through as the lights changed to red or I would have been into the back of him. I was then stranded in the middle of the road as cars went all around me. I think the problem must have been air in the braking circuit. I can only assume that clutch pedal operation was sucking air back in through the leak and aerating the reservoir.

Steve
Steve Gyles

I believe that the extra volume in the disc brake master cylinders is due to the use of fluid to constantly keep the brake pads next to the rotors. In a drum brake system the wheel cylinders return to their rest state, and the shoes don't stay close to the brake drums.
Larry,
I bought it off Ebay. I have it packed up right now, as I am in the middle of a garage demo to build a new, larger one.
mike parker

Mike
Remember there is what amounts to a one way valve at the end of the brake side of the master cylinder (not present in the clutch cylinder) and this keeps a few psi in the system and controls the movement of the caliper piston. In effect this small residual pressure keeps the piston very slightly pressed against the disc. This is why an MGA wheel with discs often does not spin freely. It is not binding as some think but doing what it has been designed to do.
John
J H Cole

Steve,

You lost your brakes, so obviously something went wrong. I just cannot understand what.

The brake circuit is an almost completely closed system. The first thing that happens when you push the brake pedal is that the tiny hole allowing brake fluid to flow between the master cylinder and the reservoir is closed by the piston. There is no real circulation of brake fluid here, just very small amounts moving in and out because of temperature changes, or when the brakes are adjusted. So how could aeration of the reservoir in this very short time bring sufficient air through this very small hole where nothing circulates to cause a brake failure?

I really feel there is another explanation here. I just donīt have a clue what it is!

Tore
Tore

Steve

You said...

"I can only assume that clutch pedal operation was sucking air back in through the leak and aerating the reservoir."

No - the brake pipe leak was leaking fluid, the MC fills with air, through the cap, until air is finally fed into the brake &/clutch cylinders. You are exactly in the position you would be in if you needed to bleed your brakes & clutch, but without fluid in the reservoir.

Like a foot pump all compressible air - useless.

Now that was worrying you had just checked the level...

Copper washers are soft and act as gaskets AND sealant.
So definitely no sealant required. Remember what I mentioned earlier about annealing & re-using old copper washers when you can't obtain new ones.

Good luck with the bleeding - remember which order to do the brakes!

Pete
Pete Tipping

Peter & Torre

I am as mystified as you about what happened. At the time I just assumed I had lost all fluid. Back home when I inspected the MC in situ it was the Clutch banjo that was sopping wet. I was even able to undo the clutch banjo with my fingers because the fibre washers had disintegrated so much. The brake side was dry. I then sucked out the residual fluid from both sides revealing the sludge and debris. Perhaps it was this sludge that caused the problem. When I emptied it into the tray it appeared to be floating in the fluid.

Despite all the logic of your arguments, and I agree with them, the brake circuit was very much on the way out, verging on useless.

Thanks for the comments on the copper washers.

Steve
Steve Gyles

Steve

I find your MC failure nagging on my mind since it should not be beyond rational explanation and there may be a lesson here for all of us running on silicone.

Here's my two pen'th:
What your calling a catastrophic failure was the end result of a leaking washer of a period of time. Every time you pressed the clutch you pressed a little more fluid ot of the reservoir until it was drained on the clutch side and ceased to work. What you say was the pool of fluid may have accumulated over a short period of time. In a sense it was not a 'sudden' failure but the end result of a leaking joint that only appeared as 'sudden' when you used up all your fluid and air entered the system. On the brake side the retained fluid in the reservior due to the middle wall was OK for a while but its possible that when you braked the fluid washed to one end and exposed the'small refil hole. This would then introduce air into the system and cause soggy brakes. It might not however cause the total failure you describe but such situations do not have the backing of much personal experience.

What your experience means to me is that I would be interested in a fluid sensor for the MC as long as it was'nt too Heath Robinson. Theres probable one out there that would convert.

John
J H Cole

Detective Chief Inspector Cole

I like it. The givens are that the MC was full at engine start-up and empty as makes no difference 3.5 miles later. Gear changing and braking appeared normal for 3 miles. At the 2 mile point was a wonderful set of sharp corners - right, left, left, right. I normally take them at about 50 with tyres just squealing. Just into the last half mile as I pulled left out of a T junction, I crunched getting into second, badly crunched into third, just made fourth, lifted, could not make third, braked hard with foot going through the floor and came to a stop. Felt a fool as everyone came around me.

Steve
Steve Gyles

Mike

Was the "kit" specifically for the MGA or was it some sort of "universal" setup? When you get your new garage finished and find it maybe you could start a new thread and provide the description so that others of us can go looking for one also.



John

I need to do some checking dimensions, etc. but you might want to check out http://www.liquidlevel.com/products_switches_standard_vt_LS-12-120.asp It is possible one of these will work out. Depends on where the trip point of the switch is vertically, vertical length of the switch assembly, diameter of the float vs diameter of the fill hole of the reservoir, volume of the float, etc. I will try and pursue this a bit further as time permits.

Hopefully someone can come up with an assembly available at your local "auto salvage yard" that can be adapted to the A reservoir that would be a bit less expensive, or available through your local NAPA or similar parts store.

Larry
58A
Larry Hallanger

Larry,
I believe that the kit ws universal, although the cap was a correct plastic cap for the MGA. It was basically a cap with a float and a wire and light. I think that the light said 'brake' on it. I know exactly where it is (in a POD) and will start a thread when I get the POD unloaded.
mike parker

This thread was discussed between 28/07/2006 and 03/08/2006

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