Advice: Brake master cylinder overhaul and fluid

[taylormj4]

Hi all,
I'm overhauling the brake master cylinder on a 1973 Range Rover. I was going to buy a New Old Stock Lockheed cylinder on EBay but I have been informed by a supplier that this is not generally a good idea as Lockheed used to require them to remove master cylinders from the shelves after 2 years as the seals would have degraded (presumably as not in fluid). So I am overhauling mine.

My question is, I have bought an overhaul kit and as this is an original Lockheed kit, it's certainly much more than 2 years old, so are those seals no good also, or are they OK as not been compressed inside a cylinder ?

Question 2 is : Anyone know if DOT5.1 is OK with old systems or should I be stick to DOT 3 or DOT 4 ?
I know that the higher numbers correspond to higher boiling points but are there any issues with older type seals and system designs with the new fluids ?

Thanks.

[paintman]

Used to work in a motor factors in the 70's & never heard that one, we used to sell a LOT of cylinder overhaul kits by Lockheed and Girling for wheel cylinders, brake calipers, master cylinders (clutch & brake) and clutch slave cylinders.
Providing they've been kept in reasonable conditions & look & feel OK I wouldn't have any issues using them.
The downside with repair kits is that they don't allow for wear or corrosion in the bores of the cylinder you're overhauling & we often used to find that we'd be selling a replacement cylinder to them not long afterwards.
On wheel cylinders (yes, I know the RR doesn't have them)I just renew the complete cylinder.

I use D0T4 in my 1986 RRC.

[taylormj4]

Thanks Paintman.
The seals felt flexible but stiffer than the old ones, which were quite floppy. It would appear better that they are stiffer. The piston certainly felt a tighter fit when re-inserted into the bore. The old piston pretty much slid out under gravity evn when off the spring.

The bore was like a mirror on most of it's surface with only a few areas with like small brown dots or stain. I wouldn't call them corrosion and they certainly felt pretty smooth and were only visible when the bore was thoroughly dry.

The master cylinder is back on the car but not bled yet. The clutch master cylinder is though and that seems to be working well and if anything that bore was the one that looked worse of the two but as only a clutch system I thought I'd try it.