TheSamba.com :: View topic - Brake pedal drops to floor, no leakage. What is this?

Wed Nov 19, 2008 10:10 pm

I bought a Fastback (72) that is in really good shape except the front fenders. Typical rust on those, but the pans and the rest of the car are rust free.

Anyway, the only major issue keeping it from being a driver right now is that the brakes only barely work. I've done some searching and didn't come up with anything exactly like this.

The brake pedal has about an inch of free play before the rod contacts the master. Is this correct? I thought it was supposed to be less, but I don't think that is the big issue and I know better than to adjust that.

PO (who is interesting to say the least and doesn't know a whole lot about cars) says he replaced the master, but it looks to me like it must have been a used or rebuilt unit. I don't see any leaking anywhere from the master. There isn't any real obvious leaking from the wheels/lines, and I don't think there is any leak at all. I filled the reservoir up all the way and even when pumping the pedal many many times, the pressure never builds and the level in the res. never goes down.

Once you take up the free-play on the pedal, it feels like the only resistance is from the spring. Finally when you get like an inch from the floor there is a little bit of resistance, and at this point according to the PO the brakes actually function to a small degree.

To me this sounds like a massive amount of air somewhere in the system/lines... Does that seem accurate? No leaking and virtually no pressure building, seems like that MUST be the solution, but before I dive in on bleeding this thing on the side of the road, I want to make sure I'm not crazy/overthinking something. Does it sound like I need to bleed the master as well? What is the procedure for that? Thanks in advance for your help. :shock:

Wed Nov 19, 2008 11:36 pm

Adjust the freeplay by moving the pedal stop plate, never the pushrod.

Sounds like a fried master, or a very poorly bled system. Could be very weak soft lines, but I doubt it would give you THAT much slack. I'd bleed it (you odn't need to bleed the master seperately) and then, if unsuccessful, replace the master. I think Jim Adney rebuilds them.

Thu Nov 20, 2008 5:18 am

Wouldn't it be leaking from the master if it was bad, though? Or not necessarily?

Thu Nov 20, 2008 10:18 am

No, if fluid leaks past an internal seal it won't leak externally, but it also won't build up any pressure to the wheels. This is the most common failure mode for a MC.

Thu Nov 20, 2008 11:29 am

Ahh. Well crap.

Thu Nov 20, 2008 2:25 pm

I replaced my master cylinder and forgot to bleed it before I put it on, never again! It seemed to take forever to get it bled out. I can't recall how many times we bled it! I would definitely try to bleed it before I went to the trouble of removing it. Just my 2 pennies, Good Luck!

Thu Nov 20, 2008 5:50 pm

It does activate the brakes, but only at the VERY bottom of the pedal travel? Does this still seem like an internal failure or no? I would think no pressure would = no pressure. The guy drove it like this for months, so it has some... just a scary small amount.

Thu Nov 20, 2008 9:25 pm

The only way to know is to bleed it completely and see if that fixes it. If not, new/rebuilt MC.

Sat Nov 22, 2008 12:57 pm

this is a new car to you.You should inspect all four brakes and adjust the rears. then bleed the brakes.

Sat Nov 22, 2008 1:30 pm

Dfasty wrote: this is a new car to you.You should inspect all four brakes and adjust the rears. then bleed the brakes.

Roger that, I'm just trying to get it home. The PO has no issue with driving it like this, it concerns me but he drove it the whole time he owned it like this. Once I get her home I'm going to be re-doing most of the brake system (pads, shoes, wheel cylinders, rebuild calipers, hoses, possibly lines).

I went to work on the car again today. Turns out it isn't not the master and it IS leaking, massively - from the left rear wheel cylinder. The front all looks good though, and the guy re-assured me that he has no problem driving it 15 miles to me house. Obviously knowng it will be front brakes alone.

Anyway, thanks for the help. I still feel like the brakes need to be bled, but that will obviously come with replacing and/or adjusting. MC is definitely brand new.