W2000 brakesystem

[Assen]

Hi,Today overhauled the frontbrake of my W2000. It had completly seized up. The piston in the mastercylinder was stuck in the full brake position. The pistons in the caliper had also seized up in the caliper (Is it seized or seized up by the way???).I completly dismanteld the mastercylinder and the caliper expeting a lot of rust and corosion. To my very big suprise everything inside the cylinder and the caliper was clean and in pristine condition. Like brandnew!!So, what was the cause of the seizing? All the rubberparts inside both items were swollen to about twice their normal size. Over the years i overhauled lots of brakingsystems and i never have seen anything like this.I allways use Dot 4 brakefluid. My thoughts are that the previous owner used Dot 5 brakefluid? I know this Dot 5 does not mix with Dot 4. But wil it make rubberparts swell?Dot 5.1 would be the better choice if you want the use the best brakefluid for your bike.Youre thoughts???Groet, Jannes

[FloridaMike]

The various flavors of DOT# brake fluids are not 100% compatible and some of them will definitely give the rubber parts in the system indigestion. Check the old-time owner's manual for the W2000, it probably specifies DOT 3. DOT 4 may swell the seals (bingo!), DOT 5 (silicone) won't mix with 3 or 4, and the new 5.1 isn't silicone, it is actually an improved DOT 4. Before you refill the system now that you've gone to the trouble of rebuilding it, check that you are using the recommended flavor of brake fluid. "Newer" or "higher number" isn't always "better" or even appropriate.You may also want to check the rubber hose to the caliper - that may now be swollen (internally) as well, and will prevent the caliper from releasing. (I once burnt out a full set of brakes on a 1968 280SL in under 100 miles because of this!)I don't like to be the bearer of unpleasant tidings, but having the front brake lock up at speed would probably be a lot more unpleasant.Best Regards,FloridaMike

[Assen]

Thanks Mike,For sure i'm going to renew the brakehose! Safety first!For those interessted in info about brakefluids ; see the website "American Auto Club UK"Go to "articles" and then read "batlle of the DOT's" Very informing!!Groet, Jannes

[kanonkopdrinker]

Hi Jannes,If you require new seals for the caliper and / or the master cylinder, drop me a line .... the club has some.David

[Assen]

Thanks David!! But.....Joe Walker allready brought me the parts. Bought from you haha!!!!!Old age creeps in....Kind regards, Jannes