The only DOT 5 vehicle in my fleet is the Harley .... mid 70s 'banana' brake calipers .... keep a bottle handy for that .... would like to standardise throughout but dismantling and purifying every little bit of the braking system doesn't appeal.

K

. That's another mod my +8 had, seems to keep a firmer peddle feel

The photo you show the rusted cylinder on is due to rust outside not internal so brake fluid won’t stop that. If it does you have leaks!
As you are doing a rebuild then now is the time to consider upgrades. That way you are only replacing old parts with upgrades so not much more £.
Braided pipes is an obvious easy one. Invest in a brake bleeder kit so you can do one man fluid changes easier either annually or every 2 years. No need to have a pedal pumper then! Dot4 fluid is not expensive so you can get fresh every time. The brake system is reasonably airtight so no big exposure to moist air. It can become part of routine checks/maintenance.

Just my twopence worth based on a couple of cars that I put back on the road for friends. Firstly a TR5 that had been asked up in a barn for 12 years with silicone brake fluid and normal Dot4 clutch fluid. The brakes worked absolutely fine but the clutch hydraulics were shot. And a Jag E Type that had been parked up 5 years where both clutch and brake circuits needed complete overhaul. In my Plus 8 four seat currently nearing end of rebuild I've asked that they put silicone fluid.

Cheers

I do a fluid change every two years. My Roadster rear cylinders lasted 14 years, which is good enough!

That's the trick, checked annually whilst 'bleeding' I also apply a tiny bead of Ceratec around the exposed pistons in the front calipers with a fine paint brush (pads out job)

So DOT 4 is ok PROVIDED you change brake fluid every other year or so, and DOT 5 is ok PROVIDED you flush your system thouroughly and get rid of absolutely all old brake fluid before you fill in DOT 5 silicone.I went for the second alternative. I know plenty of Morganeers that do not remember when they changed DOT 4 last time - possibly dangerous, but to err is human.
I took exeptional care with flushing when I changed to DOT 5, so I think that problem is taken care of once and for all. And I need not worry about the DOT 4 absorbing water and thus lowering the boiling temperature, neither the water content in the fluid sinking to the bottom of the system possibly inducing corrosion, when the car is stored for a long time during winter. So silicone for me. Cannot see why not, again provided you do the fluid change job to perfection - once. Now, I have a fairly modern car - 2004, so there should be no issue with rubber sealings, gaskets etc.Wether this is a problem with old cars, I do not know.

All brakefluids have light and shadow. And: you can‘t easy change from one fluid to another.

You must change all rubbers and clean the whole system. Two years ago I want this for a bicycle. All cleaned, all rubbers new
and all blowed through with high pressure. The brake works for two or four rides.

The do a rustprotection use this:
https://www.amazon.de/ATE-03-9902-0...hy=9044511&hvtargid=pla-540844569316

Greets René

Am I right in thinking that Silicone brake fluid and synthetic fluid are not the same ? I can buy synthetic that is Dot 4 compliant, is that compatible with”normal” fluid. If so what’s the advantage of synthetic?

When I rebuilt my 4/4 with a new braking system, that includes new master cyclinder, calipers, kunifer brake lines, wheels cylinders & stainless brake hoses. I filled it with silicon brake fluid.

It has been faultless, I ran the original fluid for 15 years and changed the fluid around 3 years ago. For a car that is used on better days, it is an ideal solution in my experience.