I'm no expert, but in the first two weeks I had my 300DT, I had to make a panic stop [for the NASCAR inspired Atlanta drivers] and boiled my brake fluid. I still had brakes, but had to almost stand on the pedal to make 'em work. After bleeding and replacing fluid [which is recommended annually], brakes were back in business. Might be something to check if the vacuum system checks out OK.

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1983 300D- silver blue, tan leather, 205,000.
1975 Datsun 280Z. Stock, ready to restore.
1983 San Juan 23. Dry docked.