512TR brake pedal soft after new pads

Hey, I installed new front pads in my '93 TR after I noticed they were almost gone while doing the suspension rebuild. I bled the brakes after installing the new pads and noticed that the pedal is now even softer than before and when coming to a long, slow stop, like exiting the freeway, the pedal will slowly go to the floor and I will need to pump again to get strong braking.

I re-bled the brakes (and clutch) using my power bleeder and didn't see any air coming out so I'm pretty sure that isn't the issue.

My friend suggested I could have damaged the old rubber in the master cylinder when I squeezed the calipers open to install new pads? I'm considering doing a rebuild of the master cylinder (this seems to be the kit -- https://awitalian.com/product/ferrari-brake-master-cylinder-rebuild-kit-95696966.html/) but wanted to get thoughts from this group before I go down that road.

 

One additional detail I forgot to mention, my TR also has the ABS module ... I did the second bleed with the key on (as suggested in another thread) but unclear if that is actually allowing bleeding through the ABS module or not.

 

Good call @Drew Altemara ... just ordered another can of fluid. I'll give it a try over the weekend and report back.

 

@turbo-joe I haven't found any leaks (and fluid reservoir hasn't seemed to have gone down at all) but will check carefully again before I bleed.

 

Pads are fine, when I pump it again the car stops just fine and yes, if I apply enough pressure ABS will engage. I'm going to try to bleed one last time this weekend with the press/release method as suggested... if that doesn't work I'm going to attempt to rebuild the master cylinder.

 

@lagunacc here is a photo of the ABS module in my car... it definitely exists and works
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Doh, my bad, I got confused when you mentioned TR thinking you were referring to the 512TR. I'm still new to this forum

 

It was a leak after all... It turns out one of the inside facing bleeders on the left front caliper was leaking so I re-bled both front calipers using the pump/release method and seems to be fixed. Definitely a slow leak because the reservoir was still full but then again I only drove it a few times after installing the new pads. I'm always a bit tentative tightening the bleeders because I don't want to damage the threads but I made sure they were tight and then pumped the brakes a few times before I put the wheels back on to ensure it wasn't leaking again. I cleaned the inside of the wheel really well so it will be noticeable if it leaks again.

Thanks all for the feedback!

 

I went for a longer drive today and its still happening... I need to recheck the bleeders again with wheels off but I'm starting to think its the master after all. Assuming there is no leak from the bleeders this time I'm going to remove the master and see how easy it is to disassemble and then decide if I go rebuild kit or new master.

 

I finally got around to removing the master cylinder and disassembling it. It was easy to remove thanks to a 13mm swivel socket I had "in stock" to remove the cylinder from the booster. I remove it from the car and then pulled off the plastic reservoir. As you can see in the first photo, there was a significant amount of rust under the rubber seals for the reservoir. I remove the snap ring and the spring and plunger, then a screw in the middle releases the second plunger and spring. The interior of the cylinder looks perfected with an almost mirror finish which I struggled to get my camera to show. I used some sandpaper and a tiny Dremel wire wheel to remove the rust. There is still a small amount of pitting on flat part of the cylinder but I think I got most of it off, including removing a bit of surface rust in the inner part of the fitting. Since the interior of the cylinder is not scored, I'm going to order a set of new seals and reassemble. I will report back after I bench bleed and reinstall.
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