I know all that, and You are wrong. It has been 3 months and 3000 km, my brakes are neither leaky nor sticking. The system was completely cleaned and filled up with DOT4 on new seals. Brake master cylinders go out on their own, too, You know.
My friend has had DOT4 in his for the past 1,5 year/ 8000 km and he even left the old seals in. Nothing wrong with his brakes.
I know that DOT3 and DOT4 are interchangeable, but DOT5 will destroy the seals for any of those two. Maybe it used to happen with different seal materials, or a different number DOT fluid, or R3 fluid which is not even close in chemical composition to DOT4, but not here.

Saurus,
As I understand you have replaced the master cylinder to a new dot one.(?)
Do you consider the remaining seals in the other 4 slave cylinders?

Saurus,
I can assure you that during the 30 years I've spent owning and working on A series Citroens, one of the most common problems with brakes has been directly related to the use of an incompatible brake fluid in the system.

The worst case I saw was a doctor in York who'd spent over a year building one of those Hoffmann kits.

Since there was a long interval between him filling the (disc) brake system with (DOT) fluid and the car going on its maiden outing, that trip ended in a recovery to our workshop with instructions to totally rebuild the brake system.

His wife refused to go near the car again, as the total brake failure when the fluid boiled had been on a rather steep hill in the Yorkshire Wolds...

Since the effect of DOT fluid on LHM seals is to cause them to swell, perhaps older components which have worn seals may not be as badly affected as those with new and closer fitting seals?

ken
( I've got about 25 LHM master cylinders in the 'might get round to repairing one day' corner and even more sets of calipers.
None of them were removed because they were leaking, but because they were seized.
Those calipers which I've rebuilt have needed a spare master cylinder to pump the pistons out, as compressed air at 110 psi has no chance of moving them )

but they are! your seals in the master have swollen and wont retract and now you have no brakes
LHM system will be ruined by using dot4, and silicone stuff rots it even faster ( 5 hours into a 24hr race ) there is no majick cure about flushing with spirit thinners etc the rubber used is incompatable - no "if"s "but"s or "maybe"

now the world has shrunk and borders dissapeared it cant be that difficult to get LHM surely?

PS the universally used Manitou agricultural tool carriers use LHM, find a local dealer and you will be able to all club together and buy a 25l drum of the stuff

[quote="SeanPS the universally used Manitou agricultural tool carriers use LHM, find a local dealer and you will be able to all club together and buy a 25l drum of the stuff[/quote]


As do New Holland/Ford JCB and most modern tractors and small plant machines.

Very interesting.
The New Holland dealer about 5 miles away is also the local depot for Engweld, so must remember to ask them about LHM next time I need a gas refill.

ken





As do New Holland/Ford JCB and most modern tractors and small plant machines.[/quote]

So what exactly is supposed to happen to the LHM rubber besides swelling? Does it dissolve, break apart or something?

Saurus,
once the seals have swollen, free movement of the pistons in their cylinders or caliper bores is lost.

As a result, the piston(s) in the master cylinder may not move back to their 'at rest' position and pistons in the slave cylinders will either be sluggish in their movement or will stick in the 'on' position.

ken

The rubber soaks up some of the glycol and it makes the rubber swell slightly and go slightly softer, which then makes them "sticky". Its a common misconception that because the seals don't fully dissolve, break up or burst in to flames then it must be compatible or the incompatible info is a myth.

it works the other way round too i was re building brakes on a vauxhaull(opel) and cleaned the dust seals with WD40 which then went all baggy and i couldnt get them back in the bores - lesson learned!

incidently the way to clear out the contaminated system is to flush it through with Gin (ECAS Roy!) - tho' Vodka may be more readily available round your way

So how is it possible that other people use it, some have for years, and their brakes are fine?
My car is out of order now, so I might as well take the time to flush the lines and put in all new seals, I have nothing against LHM and it's not hard to come by, I was just persuaded otherwise
I dismantled the master cylinder. The rear seal of the front piston got caught in between the piston and cylinder bore.