[fastrehotrods]

Well mostly. Here's my problem. I just picked up a 68 Cadillac Eldorado that I've been driving for the last few days. It's been driving fine until today when I was driving it after it was all warmed up. I went to hit the brakes, then my foot went almost to the floor! Almost, cuz when I floored it that last little bit it locked some of the brakes up, I'm thinking the rear? Anyways, nothing was odd about it when I picked the car up except that the rear reservoir of the master cylinder was dry. I filled it, and it has been fine since just now. Any ideas? I was driving this thing since my blazer is down, and now I fear rearending another car with my 4600lb Eldorado!! Thx.

[poncho62]

Is the resevoir dry again?........If so, there is a leak in the system. If not, try bleeding the brakes....which you should have done the 1st time, when you found it dry.

[fastrehotrods]

The reservoir did not go down one bit... if anything it looked more full than it was before? Probably just imagining things.

The reservoir wasn't dry as in bone dry, it was just very low, with a little bit on the bottom. I filled it up a couple weeks ago and it has been fine since, but I think I'll bleed it when I can just for assurance. There is no correlation between that and the engine being hot is there? I noticed that it was pretty warm under the hood when it was doing it, but I would think the car was designed to prevent heat/brake issues back then.

[Henry Highrise]

If you have a brake locking up or grabing then you must have a wheel cylinder leaking. Thats prpbably why the master was low.

[poncho62]

Sounds like the seals in the master cylinder have gone for a dump.......

[fastrehotrods]

I think the brakes were locking on the one circuit because of me flooring it because the other circuit wasn't working. Now that you mention it, a master cylinder does sound pretty possible.

I don't think it's a wheel cylinder because I've had them go out before, and it didn't feel like that. The rear circuit seems to work fine. I guess the rears locked up because I have ALL the weight up front (engine, transaxle), and nothing to hold the rear down. That's probably why it felt like I wasn't doing much when I floored it!

I don't know if the calipers are bad, but I'll check them as well. But I'm thinking the master cylinder idea sounds very possible! THANKS!

I would've normally figured it out eventually, but my brain is tired from trying to figure out why my blazer isn't running right! I'm supposed to drive these, not always fix them!

[matt167]

fill the master, bleed out 1 front and 1 rear wheel cyl/ disc, if theres air, do the other's, if not, get in the car, hold your foot on the brake, start the car, the pedal should take 1 step, then hold for 60 seconds, if it goes down slowly or begins to start to go, it's probably leaking sealing cups, allowing fluid bypass.

[fastrehotrods]

But come to think about it, when I'm at stoplights holding it still in gear, the pedal doesn't drop, nor does the car creep forward? It seems to be holding, at a stop, but when I need to stop from speed, it intermittently does it.