Morris Minor Owners Club

having replaced the front drums and shoes for brand new from ESM, THE mot man isn't happy that although the front brakes are spot on the rolling tester machine, the brakes bind/stick a bit after breaking, upon removing the drum I find there is a "spot" he's suggested rubbing back the brake linings with emery paper, but could it be my three year old wheel cylinders are the problem, failing to return and causing the partial binding against the drum? does anyone else have a similar experience?[frame][/frame]

If you use silicon brake fluid, no more seized cylinders to worry about!

so the cylinders are known to seize with non silicone brake fluid, that could be my problem then[frame][/frame]

Those brake shoes need the high spots removed and to be bedded in. Brake shoe dust as a result of bedding in does not help either.
Never seen the need for silicon brake fluid myself. I just change the brake fluid at regular intervals which helps preserve the life of the brake components.
If the car is little used - exercising the brakes by regular pressing of the brake pedal helps too.

You may need to have the shoes radius ground to match the curve of the drums.

Thanks for the replies Katie and Gents, the cylinders are well gunked up and jammed up only one side, but that's without the pressure of the drum being fitted. So I may still be barking up the wrong tree.[frame][/frame]
I've ordered new cylinders from ESM so they should arrive tomorrow morning, I've also purchased some of this to replace what is in there now. I'll have to drain the system and bleed out any air bubbles when I add this new synthetic stuff.[frame][/frame]

Dave,
Whoa !!
When replacing Mineral based brake fluid (the DOT 4 you have in at present ) the strong recommendation is that
"all " the rubber seals in the braking system should be replaced BEFORE putting in Synthetic brake fluid DOT 3.The system
should be flushed through with DOT3 to eliminate any contamination with the old DOT4 fluid.

The reason in layman's terms is that the old rubber seals will deteriorate rapidly, when exposed to DOT3.Result No brakes !!
If I where you, I'd install the new rear brake cylinders from ESM, bleed and top up with existing old school DOT4.
My bet is that the new cylinders will cure the problem.
With it all reassembled and the wheels still up in the air,car on jacks,spin the wheels to see if they rotate several revolutions
without binding and coming to a halt under their own momentum.

If that test is OK you could, with a willing assistant, repeat the exercise but this time with very ,very light application of the foot brake.
To identify where the high spot is, ( assuming the leading edges of the brakes shoes were lightly chamfered when they were first installed you can try the paper test.
Just as you would run a strip of paper down the gap,when a wooden door was jamming, use the same principle with the brake shoes.Strip of paper held at 90 degrees to the shoe and move it around the perimeter of the drum.
Brake adjustment should be between the brakes "locked on " and a 90 degree click on the adjuster, to back off the brakes, when it is free to rotate.
Increase the thickness of paper / substitute cardboard, what ever to identify the high spot, then rub down.
When you brief the MOT man / woman, they normally appreciate your efforts and will acknowledge that new brake shoes /drums require a bit of bedding in, on the road ,before they start to operate a full efficiency.

See how it goes.If you want new seals all round , now , with synthetic DOT3 fluid you'll need a new master cylinder / or seal kit at least, new front brake wheel cylinders.Quite a bit of expense.
Alternative stick with what you've got and use the DOT 3 synthetic on the modern Eurobox when the time comes.
Bob

STOP! DOT 3 is inferior to DOT 4 and it is NOT 'silicone' brake fluid. It is perfectly adequate for a Minor's brakes - as is DOT4 (they are all 'synthetic' ) And DO NOT put DOT 3 in your 'modern' - it needs DOT 4. Silicone fluid is DOT 5 and costs a fortune. And yes - you would need to renew ALL the rubber parts in the brake system - flexis/master cylinder/wheel cylinders....... if going to DOT 5. It is reputedly slightly compressible - and so can give a soft pedal... NO modern car manufacturer uses DOT 5 - certainly not any of the mass producers.. I hope you have ordered the more expensive 'genuine' wheel cylinders. The cheaper cylinders are hopeless........ In fact I think all you needed to do was to remove the pistons and clean them up - before refitting with a dollop of RED RUBBER GREASE. Use that anyway with your new cylinders......... http://www.ebay.co.uk/itm/18g-Castrol-R ... 1e6d1c5b18

Yes dot 4 not 3! ---and this silicon debate crops up here from time to time. Some folk don't approve, so do. I've used it for many many years and haven't suffered any ill effects yet. Although it hasn't stopped my clutch plate sticking after standing for a few months!

There is no way that you should need to change 3 year old cylinders, 30 years old, maybe

I'm not advising against the DOT 5 , although I don't use it myself..... Just warning of what's involved to make the change.... Perhaps if doing a complete rebuild of the braking system it could be worthwhile...each to their own. A dollop of red grease keeps moisture out and pistons sliding nicely... It's a lot less money........

ok, thanks all for your replies, I'll stick with dot4 then, as I've already paid for new front cylinders I'll fit them tomorrow, clean up the old cylinders and place them in the spares box. It's my last day for re-test tomorrow so I'm going to be rather busy first thing. Thanks for the tips.

You had better do an all nighter... The brakes will still need bedding in........ Remember it's 10 WORKING days - so if they weren't open on sundays you should have two extra days...... I always arrange my MOTs to give me that extra margin......

les wrote:If you use silicon brake fluid, no more seized cylinders to worry about!

Lockheed Racing warn.

"SILICONE BRAKE FLUIDS - beware
Our technical service department is receiving an alarming number of calls from motorists reporting problems with silicone brake fluids.

AP LOCKHEED NEITHER MARKETS SUCH FLUIDS NOR RECOMMENDS THERE USE WITH OUR OWN OR ANY OTHER BRAKING SYSTEM.

Virtually all problems relate to:
- long/spongy pedal
- sudden loss of brakes
- hanging on of brakes

They reflect certain properties of silicone fluids identified by us over many years and recently ratified in SAE publications, namely:
- high ambient viscosity
- high air absorption
- high compressibility
- low lubricity
- immiscibility with water

Research has shown that the relationship between problems reported and problems identified may be expressed as follows:

LONG/SPONGY PEDAL
a) compressibility, up to three times that of glycol based fluids.
b) high viscosity, twice that of gylcol based fluids, leading to slow rates of fill and retention of air trapped during filling and hence bleeding difficulties.

SUDDEN LOSS OF BRAKES
a) Air absorption. Gasification of absorbed air at relatively low temperature produces vapour lock effect.
b) Immiscibility (failure to mix) with water. Whilst the presence of dissolved water will reduce the boiling point of glycol based fluids any free water entrapped in silicone filled systems will boil and produce vapour lock at much lower temperatures (about 100 deg C).

HANGING ON OF BRAKES
a) Low lubricity. In disc brake systems the sole mechanism for normalisation upon release of pedal pressure is a designed-in tendency of seals to recover to their at-rest altitude. Low lubricity works against this tendency
b) High viscosity, exacerbating the effect of a) above

Oh well, Good job I don't race my Minor then! Perhaps they should ban the stuff.

katy wrote:You may need to have the shoes radius ground to match the curve of the drums.

Anybody know where you can get shoes radius ground please
.

Crikey - it's a lot worse than I thought.....

davidmiles wrote:Thanks for the replies Katie and Gents, the cylinders are well gunked up and jammed up only one side, but that's without the pressure of the drum being fitted. So I may still be barking up the wrong tree.[frame]

Does anyone know the effect of Gunk on brake seals.
I suspect it does irreparable damage.

Sorry if I am the bearer of bad tiding David
There is a special spray for brake cleaning.
.

Has anyone had any success with a Brake Honing tool? Doesn't cost the earth.
https://www.cromwell.co.uk/KEN5032940K

Trickydicky wrote:Has anyone had any success with a Brake Honing tool? Doesn't cost the earth.
https://www.cromwell.co.uk/KEN5032940K

Yup, plenty ;-)

But not with Cromwells.

I staple a length of 1/4" thick foam to a 1/2 dowel.
About 4ft of dowel.

Wind some fine wet and dry round the foam.
I start the W&D in the foam.

Fit the dowel on my electric drill.
Poke the W&D end inside the cylinder.
Slop some WD40 in.
Run the drill.

The length of the dowel encourages a the W&D to centre.

Most notable success was with some lo0ng hydraulic rams.
Nearly 4ft long hence the length of the dowel
.