Brakes don't wanna brake!

[patrick66]

I recently replaced the front disc brake calipers on my '66 Coronet with new ones about four months ago, because the previous units were sticking badly. The car was converted to '73 - '76 A-body front discs and the master cylinder and proportioning valve from the donor car ('73 Dart Sport) in 2003. The last time, prior to this Spring, that the car had any miles put on it was 2011, so the brake calipers ended up sticking.

Replaced the calipers, bled the brakes and went off to drive the car. It ran and stopped great...for awhile. I went to drive it a couple of weekends ago, and the pedal felt weak and spongy. On a downhill driveway onto a public road, I damn near couldn't stop the car! The reservoir was full. The brakes felt like they had air in them, and the fronts once again feel sticky. I can find no leaks anywhere.

Any ideas???

 

[65sporty]

When you say sticky I assume they are dragging? Have you bleed them again? How old are the front brake hoses? I have seen a hose cause brake drag

 

[patrick66]

The hoses and everything else was replaced with new parts in '03. The brakes now aren't really sticking, per se, but they feel more like they are weak and not engaging properly.

I'm looking to re-bleed them tomorrow or Thursday, as I'd like to take the Coronet to Cars-n-Coffee this Saturday.

 

[KcImperial]

I would block the lines to the master cylinder and bleed it first to make sure you can get a firm pedal. Suddenly having a spongy pedal and no signs of leaks is usually a bad master cylinder.

 

[patrick66]

Good point. I'll work that angle first and go from there.

 

[traintech55]

Does sound like a bad hose. Jack up the front end and try to rotate the wheel and tire on each side. If they turn freely then have someone apply the brakes and make sure both sides engage, if so have them release the pedal and check again. If one side is dragging you will be able to tell.