Houston, I think we've got a problem (with brakes)

[CorsePerVita]

Ok. I just got this 914 not long ago. It's a 1970 Porsche 914, 1.7L.

It has new brake lines installed by the previous owner before I bought the car. We took it out and drove it, all was fine. I purchased the car, and on the way home, out of nowhere I had no pedal pressure. Pumping it up worked and there was again good pressure. Then they went out again. Again.... pumping it up gave me pressure.

If pedal pressure was applied - it would not go to the floor, it would STAY FIRM. If you let off and re-applied, no pressure till you pumped it up fast enough to get some pressure to hold it down.

Oddly as it was... I limped it home and about 5 minutes into the issue the issue went away and never re-appeared. I bled the brakes and there was no air. I took it for a drive, it was fine.

Today... weeks later, the issue again appeared. Having thought perhaps it was a stealth bubble I bled, the issue was again the same symptoms.

This is leading me to believe I Have a bad master cylinder. I DO have an extra master cylinder for the brakelines that the previous owner has supplied which is for a 911 (but will fit).

Brakes are far too important to skimp on. I thought the issue was air but I'm thinking it's not - could someone confirm my suspicions? Another thing - there is NO FLUID LOSS. I also appear to pull slightly to the right and the front right brake appears to be working overtime compared to the others? I've got massive amounts of brakedust there and she pulls to the right pretty hard, dragging a brake perhaps?

[Dave at Pelican Parts]

Sounds like a bad MC is a definite suspect with those symptoms.

--DD

[Joe Ricard]

effed up caliper on one side.

I would rebuild both fronts because you really don't want to do just one.

[HarveyH]

Long long ago in a galaxy far, far away, my sister had a similar problem. Of course this was on a Plymouth Horizon, but for informational purposes...
It turned out she had an exhaust leak that blew against one of the flexible hoses for the rear brakes. Hose got hot and when pressure was applied it would balloon slightly. Pump the brakes a few times and it cooled it down and firmed it back up. Brakes would then work fine until the hose heated up again. Of course everything worked fine in the driveway because everything was cool... replaced the exhaust and the hoses and everything was fine.
Harvey