Regularly check that the brake fluid reservoir cap is not cracked. Brake fluid is very aggressive, you should always avoid leaks.
The rubber cap up to 7.1960, which is also used on a specific tank for Volkswagen Buses up to 7.1967, has a very small hole for ventilation. Do this if necessary to prevent the reservoir from emptying, which could affect braking performance.
The all-black brake fluid cap for later builds has a removable cap that is sandwiched in the cap. The cap can be removed for additional ventilation if needed. From the inside, use a thin screwdriver to push through the lower vent holes and pop the cap out.
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