Rear brake reservoir deformed and empty!

I was inspecting my 2000 WR400 today and found the rear brake reservoir empty and very dirty. It appears the plastic is deformed near the top alllowing the brake fluid to leak out just under the lid. I am wondering if this has happened to anyone else? Is the deformity due to the exhaust being so close to the plastic? It has been suggested that maybe there is a chemical reaction between the brake fluid and the plastic? I was also thinking maybe replacing the master cylinder with a 2003 that does not have a separate plastic reservoir. Any comments or thoughts would be helpful! :)

it could be due to the exhast or the brake fluid boiling because it was old and contaminated w/ water. I would replace it w/ one of thous extra capacity ones. mite as well upgrade since you got to get a new one one way or another.


the exhaust pipe melted it,

my son's wr4 had a crack near the top of the brake reservior

becos of the heat,

we have put in a new one & wrap it in some heat film to ward off

some heat. :)

my2000 did the same thing, too close to the exhaust.

I just ordered a new one from Yamaha of troy, and will wrap it with heat reflecting tape. Bad design.............

Same thing on my 99WR400. I put a few washers between the reservoir and the frame and added about 3/16" from the exhaust. Before I install the new reservoir I have on my workbench I'm going to make a small heat shield and coat it with the reflective tape so I can get to the reservoir to fill and check. When I'm done with the template I'll post it if anyone is interested (this week).

I'm running the WB E-series pro-meg exhaust. What exhaust are you all running?

Yep my yz400 did the same thing. They are only like $12. Buy a spare to have around just in case.

Thanks guys! I ordered a new plastic reservoir per your suggestions! I also run a White Bros. E pipe. I am constructing a heat shield to ward off excess. Thanks! :):)

Mine did the same thing. Got to build a heat shield thingy too. :)

Mine wasn't leaking but broke in the middle of the tab that holds it to the frame.

It could be empty because as your brakes wear the cylinder is forced out further.

Check your pads.

mine is also melted and cracked due to the exhaust. The whole system was contaminated due to the damage. i have had to replace the whole system. but am now having trouble tracking a new reservoir. any suggestions.

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