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[Enrique]

I drove my ’85 a short distance from home and started smelling a metallic burning smell. A few minutes later my brake pedal went to the floor. When I pumped the pedal, the brake pressure built back up and the brakes worked. I drove the short distance home, pumping the brakes at stops. I checked the brake fluid level and it was fine. I don’t see any brake fluid leaks. Any ideas about what is wrong?
Thank you!

[Giuliettaevo2]

If you have old brakefluid and heat it up it gets thin. A mastercilinder with some wear might get some internal lekkage then.

Had this in my 156. Clutch gave some problem, brakepedal went to the floor after a long drive with hot weather. Changing the fluid cured the problems.

[KevinR]

Rear calipers tend to seize up and then bind . This will cook the fluid , however most times they don't unstick themselves when this happens . Normally a result from handbrake mechanisms jamming on left calliper or cable popping off if installed incorrectly . Jack up rear of car under Dedion and see if both wheels turn freely . Apply handbrake and then release . Do same on front obviously no need to use handbrake
At least you can rule out binding callipers . If all good might as well bleed the system . Only use good quality 7mm ring spanner on rear nipples . Don't want to round them . Probably only time you want them hexagonal

[Enrique]

Thank you both very much. The brake fluid was last changed in 2012. The car has had very few miles since 2012 (sadly), but I assume the brake fluid should be replaced anyway. I will test for binding calipers this weekend and will post my findings. I might have some questions on the brake fluid replacement procedure. I have a Mityvac brake bleeding tool, but it's been years since I've used it. Thank you again!

[75evo]

I agree with Kev's suggestions. Could be one of the pistons is binding. Won't hurt to cleanup up the pistons. Then check the rear caliper clearances with a feeler gauge and adjust as needed. Check that the hand brake isn't causing one of the rear pistons to bind.

Buy a reverse bleeder kit. It will save you A LOT of time AND brake fluid.

MaxproHD-reverse-bleed-diagram.jpg (54.15 KiB) Viewed 5737 times

Just open all the bleed screw and let all the fluids drain out over night.

Then start reverse bleeding

http://www.brakebleeder.com/wp-content/ ... iagram.jpg

You can make a reverse bleeder kit with an oil can spray and cheap hoses.

I literally bled my 164 Super's clutch cylinder and master cylinder in 10 seconds. I see people on 164 forums saying they've pumped and pressure bled for days and still end up with low pedal pressure. Reverse bleeding is the way to go.

Check the youtube video below.

https://youtu.be/lW770mbruM4