Front brake cylinders

[michael4]

In the last year I've had to un-seize a couple of brake cylinders. It is annoying.

Looking at a well known suppliers website they show two options for the late car.

One is 'pattern' and has a seal, the other is 'genuine' Lockheed and has no seal.

Is one better than the other, ie is one without a seal less likely to seize than one with?

One costs 6.90 per cylinder and the other 23.95 both ex VAT.

OK so safety first etc but none the less I wonder...

[svenedin]

Personally I never skimp on brake parts. I have heard from an MMOC member whose pattern cylinders suddenly started to pour brake fluid whilst out driving and this caused total brake failure. He managed to stop safely using the handbrake.

The reason for seized cylinders is usually water in the brake fluid causing internal corrosion in the cylinder bores. Regular complete changing of brake fluid is recommended; at least every 2 years. Or you could consider switching to Silicone brake fluid.

Phil, who posts often on here, recommends not adjusting the cylinders up too tight so that the cylinders have a longer travel and return when operating the brakes. This also makes seized cylinders less likely but it does give a longer brake pedal which is a bit unnerving.

As to rear cylinders, leaving the handbrake off and chocking the wheels reduces the chance of seizing if parking up for an extended period.

Stephen

[ManyMinors]

I have only once fitted the pattern cylinders to a Minor. They failed (leaking fluid) in a very short time and I replaced them with the so called "genuine" cylinders. These can be serviced by fitting new seal kits if required. I have never had any problem since. Cylinders generally only stick on cars which have little use.
Despite the cost saving, I would never use the cheap pattern front cylinders again. I have never used the silicone brake fluid myself but I know that many owners swear by it.

[michael4]

I'm confused, these described as genuine Lockheed have no seals at all whereas the cheapies (and the ones currently on the car) do.

https://www.morrisminorspares.com/brake ... i-p1238344

[svenedin]

I'm confused, these described as genuine Lockheed have no seals at all whereas the cheapies (and the ones currently on the car) do.

https://www.morrisminorspares.com/brake ... i-p1238344

Yes I didn't really understand that either but these are the ones I have used. Actually, those cylinders are sitting in my garage still attached to the backplates as I have increased the size of my front brakes to 9". I will have a look later or give ESM a ring and ask them.

Stephen

[svenedin]

It is correct there is no piston rubber seal on the more expensive cylinders from ESM. There is only a rubber dust seal on the cylinder; no seal on the piston.

For those of you who remember glass syringes, the seal is entirely from precision grinding of the piston to match the barrel.

So in theory these cylinders should give trouble free operation for many years as there is no seal to fail but if they corrode internally, they're wrecked.

Stephen

IMG_2700.jpeg (2.1 MiB) Viewed 3926 times

[michael4]

Thanks, that's a great help. Now I need to decide how far to go.

The brake fluid from what I have seen is averagely cloudy. Obviously I should drain the system and start afresh when work is done, particularly if I am spending money on 'better' components.

So...replace the front brake cylinders and double check rears that have given no trouble.

What do I do about the master cylinder? It works and gives no bother and doesn't leak, I am conscious of the comments regarding corrosion wrecking seals if pumped a lot when empty.

Shall I go ahead with new front cylinders and fluid and see how it goes or am I kidding myself?...and do I stay with dot 4?

[svenedin]

Just my thoughts: if you are going to replace cylinders you are going to have to bleed the brakes anyway so worrying about what happens to the master cylinder seals when the pedal is completely to the floor is academic really because you would have to do that unless you bleed via a different method. It is better to find out there is a problem with the MC at home in the garage rather than doing an emergency stop out on the road..........

Changing the fluid is a bit of a bore due to the small fluid capacity of the MC but if you use an Eezibleed kit (with modified unvented MC cap) it gets changed automatically. Go round the whole car starting with the cylinder furthest from the MC and get rid of all of the dirty cloudy brake fluid. Then you're fine basically for 2 years and you can decide at your leisure whether you want to go to Dot 5 Silicone at some point. I changed over years ago and I would never go back. Or drain all the old fluid out and change to Dot 5 Silicone now. It's up to you.

Stephen

[michael4]

Thanks for that, your application of a little logic helps me considerably.

Michael

[svenedin]

Glad it was of use.

Stephen

[ManyMinors]

It isn't that the original type front cylinders don't have a seal. They do. However, the seal is inside the cylinder and not immediately visible as it doesn't come out with the piston. All hydraulic cylinders require a seal. Otherwise the fluid will leak out With these original type cylinders, the seals can be replaced by purchasing a seal kit, dismantling the cylinder, checking and cleaning out the bore and re-assembling with the new seals and a smear of rubber grease. This was common practice years ago when new car parts were proportionally more expensive than labour. More common nowadays to simply purchase and fit complete new cylinders I suppose.

[svenedin]

Ah! So the seal is in the bore. I didn't look carefully enough

Incidentally, my comment about glass syringes is correct. They really don't have a seal because they're for use with chemicals that would destroy a rubber seal.

Stephen

[Bill_qaz]

Its the same set up on brake calipers,at least the many I've rebuilt, the seal is in a groove in the bore and the piston is plain. It's the seal distortion that pulls the piston back slightly on release of pressure, no return spring on brake pads.
Sadly due to labour costs, very little is repaired these days. Replacements mass manufactured in countries with lower labour cost and often inferior materials has become the norm in our throw away society.
It was very different world when our cars were manufactured, as I well remember being an apprentice mechanic in the 60s for a company with a large fleet of vehicles. Most components were reconditioned in house and reused.
Recycling is by no means a new concept

[Michiel]

Incidentally, my comment about glass syringes is correct. They really don't have a seal because they're for use with chemicals that would destroy a rubber seal.
Stephen

No, these syringes don't have a seal because a seal can't be sterilised, and also the syringes were/are reused

[svenedin]

Incidentally, my comment about glass syringes is correct. They really don't have a seal because they're for use with chemicals that would destroy a rubber seal.
Stephen

No, these syringes don't have a seal because a seal can't be sterilised, and also the syringes were/are reused

No doubt but syringes are not reused these days. Certain drugs attack plastics and rubber. Paraldehyde for instance.

Stephen

[michael4]

I ought to have realised that the seal would be in the bore. Thanks for telling me.

I spent some time last winter replacing the seals in two suspension cylinders from our Citroen GS. Once on the workbench it wasn't that hard but I felt a bit nervous when getting the seals back into their rings without distorting them (they were expensive). Fortunately all went well.

[Bill_qaz]

Screenshot_20251026-144333_Chrome.jpg (44.41 KiB) Viewed 3758 times

You can buy a tool. Its sort of pliers that make the seal heart shaped, so it fits easily into the bore, then released it goes back to round to fit in its groove.

[michael4]

Thanks, yes I'd heard of this tool but only expected to do the job once. There was (in the suspension cylinder) a rubber seal which was easy to locate but the one that looked like it was made from nylon and went over it didn't seem to like being bent into a heart shape.

Anyway, that job is done.