My son's car hasn't been used much during the recent shutdown, but he went to drive it yesterday and it has zero braking. The brake fluid reservoir was empty, but I cannot see any sign of leaks. Added DOT3 but pumping the brakes offers no resistance. Prior to this the brakes were lousy, had to push real hard.

Any advice? I'm tempted to replace the master cylinder but given so much corrosion underneath I probably need to replace the calipers as I may not be able to bleed them. I'm not even sure if it has drum or disk brakes.

Thanks!