A full purge is certainly required. It will cause brake part failure due to water ingress, even though its less hygrospic, the rubber lines, seals and hardware is not, so water will get in. Since you will be checking those parts, it won't be an issue.
The silcone fluid is probably why Dearborn and Flint engineers started out sourcing siliocone fluid compatible brake parts to Australia and sent there best Flint and Milbrook engineers to do brake tests there, because Aussie conditions with Death Valley ambient air temparatures while you guys in the northern Hemisphere had winter. The Aussies had predominant two lane precoat chip and bulk bitumen "tar" macadam blacktop making the road conditions much hotter than US cement, along with shoulder bull dust. silt washouts, world class high road roughness and the worlds worst maintenance patches ment they did all there brake system testing in six weeks with a fleet of 1985 GM products in July 1984. Russelhiems GM Opel engineers tested the whole of there Bosch three and four channel ABS systmes for the Opel Monza and Senator in a few weeks with heat readings that were off the scale.
In those early days, the Aussies via Ford and GM Holden in Australia, who excell with four wheel disk brake systems the envy of the world (F cars used Holden Commodore disck rear brakes, and 84 Corvettes and Fords Cobra and Bullet in Fox 4 Mustangs ran Aussie PBR and Brembo brakes ex Ford Falcon for years) went to the high boiling point Castrol fluid. They did an ASTM or SAE test which when the boiing point drops indicates the reduction is due to amount of water present.
In Australia in 1979, and again in 1983, import vehicles ended up loosing brakes at Castleregh drasg strip where Wheels Magazine did 1/4 mile testing. There was a W123 Mercedes Benze 280E and a Mazda 323 Twin Carb SS, each suffered total brake failure when Wheels Magazine were doing there normal 100 mph brake tests.
The Daimler Benze summary from its engineering team was that the 6 week journey to Australia via container ship was enough to allow hygroscopic water ingress, with the boiling point reduced about 50 degrees F. In normal operation on most of Austrlias highways, no problem, but under repeat heat situations, brake failure could result, so DB affirmed that Wheels Magazines experience with brake failure was valid, and DB then instigated a full brake fluid change on arrival in the Antipods. Numerous reports in Wheels comonaly showed that the Aussies were taking there low spec W126 380SEL's and 380SEC's up to 140mph on downgrades, even though they had trouble making 125 mph on the flat with our US spec emissioned 195 hp 3.8 Liter engines. Anyone in Australia will understand.
Mazda Australia ruled the same thing with the SS sedan, that the fluid was new on export from Hiromshima, but they deemd the fluid to be within spec on Australian soil in Sydney. In Wheels instance, that repeat high speed stopping had shown the boiling point was below the recomended amount. The issue was unresolved, but Mazda was checking the spec of the brake fluid and if problems were detected, they promised to change the fluid.
About 1982, Wheels showed pictures of the US army changing all there Jeeps over to silocone brake fluid.
The issue was that old Corvettes prior to 1982 were a service nightmare, and the Aussies with there 144 mph 3500 pound 351 Falcon and 3300 pound 308 Commodore sedans which often got hooked up to a trailer hitch for a 16 foot boat were far ahead of the brake component game than the Americans, so the US engineers just bought Girlock and PBR technology from Falcons, Commodores and got them to supply the whole system, with silocone fluid included. At Milbrook and Dearborn, the best proving ground engineers in the world would test Aussie systems, and give them feedback so the US industry got the upgrades for free, pretesting Mustang, Firebird, Camaro and Corvette systems one or two years before the US got them.
The 1984 Corvette brake system was tested in New Zeland Benson and Hedges sedan car racing with New Zeland assembled Commodre SS 5liter sedans with 300 hp homologation engines.
