parking brke

[donm]

My parking brake has never held very well so I figured I'd start from scratch and replace the original calipers that have I think been on there since 1979. Before I start are there any special tricks I should know? Am I right in thinking I have to screw in the piston so the pads will fit? I can't understand how the parking brake works. TIA.

[18Fiatsandcounting]

The parking brake is a poor design to begin with, and it's very common to have problems. Here's how it's supposed to work: As the rear brake pads wear, there is an internal screw plunger in the rear caliper that is supposed to slowly unscrew and keep the parking brake working as it should. That's the theory; here is the reality: It doesn't work that well.

Yes, you will likely need to screw in the piston (with a large flat blade screwdriver) to get new pads to fit.

Here's the trick that I use to "fix" the parking brake. Sometimes it works, but not always. Adjust the parking brake cable so that it's tight when the handbrake is pulled up by 4 or 5 clicks. Now comes the fun part. Alternate between stepping on the brake pedal and pulling up on the handbrake, some simultaneously and some one after the other. However, do this 200 times or so. Do it until you are cursing this "18Fiatsandcounting" yahoo and his ridiculous advice. When I can feel your wrath directed at me from wherever you are, you might be getting close. Do it some more.

As I said, sometimes this works to greatly improve parking brake function.

-Bryan

[TX82FIAT]

As Bryan mentioned, start by adjusting the emergency brake cable at the junction just in front of the rear axel. If the brakes are functioning well it is highly likely that adjusting this older stretched cable will do the trick.

[dinghyguy]

The screw mechanism connects to the caliper piston deep in the piston. There is a snap ring a washer and some other bits, all of which get gunked up along with the screw itself. There is not really any brake fluid flow past the or around the mechanism. So if you are unable to free the system by multiple operations you can always disassemble the caliper, disassemble the mechanism in the piston, clean lube and reassemble. If you are feeling rich you can buy the rebuild kit with new rubber bits for less than 10$. I recently got a pair of old calipers and that is exactly what i am doing with them. Then i will swap them into one of the fiats and rebuild the ones i take out as spares.

cheers
dinghyguy

[Anbele]

All very good and sound advises, but I think that for the cost of a new cable ($22), that’s the place to start.
Pay attention when installing at the pivoting “barrel-like” part of the caliper, where the sleeves of the cable sit. It has two different dimensions. You want the metal sleeve to fit snugly in there. And keep in mind that a new cable will feel snugly at the begging but it’ll stretch with time.

[donm]

Regarding my poorly operating parking brake as mentioned above, I did replace both rear calipers and the cable. The parking brake works great now but I noticed the brake peddle has a longer travel before it starts engaging. This car has always had more free play in the peddle than most cars I've owned but now it seem like there's even more.

I did bleed that circuit but it doesn't seem like there's air in the system. I even tried adjusting the acorn nut out a bit, maybe a bit more than the specified 2mm but it didn't seem to help. The brakes do work; I can lock them up if I need to but I'm wondering why the peddle free throw is longer now. Any thoughts, Bryan? Anyone?

[18Fiatsandcounting]

I always have thoughts, although only a few might be useful...!

Is it possible that your brakes were not working correctly before you replaced the calipers, and now it feels "weird" to have them working better? These cars do have power brakes of a sort (vacuum assist), but they don't have the same pedal feel as a modern car. Some free travel is, well, normal.

Something to check:
The brakes should start engaging (just very slightly) when the pedal is pushed more than about one inch. Put the car on a level surface, engine off and in neutral, and have an assistant roll the car. Push on the brake pedal one inch. The car should slowly come to a stop. If it takes more than two inches or so of pedal travel before the brakes start engaging, you have too much pedal travel.

Causes of too much pedal travel:
1) Incorrect plunger/acorn nut adjustment. Sounds like you already tried that.
2) Air in the lines. I know you bled it, but these cars are notorious for being hard to get all the air out. Try bleeding again.
3) Pistons too far retracted in the caliper. It can happen with an incorrect master cylinder, but I doubt that's the problem. This happens occasionally on the rear brakes, and one "cure" is to tighten the handbrake a little more. I lift up the rear axle, and progressively tighten the adjustment nut in the center until the wheels start to drag when I turn them by hand. Usually the drag will stop when I work the handbrake lever a few times, and if not, loosen the nut slightly. The handbrake should lock up with 4 or 5 clicks. Ideally, each rear brake will start to drag the same amount after about 2 clicks of the handbrake lever.

If all else fails, sometimes the "pump the brakes and work the handbrakes until your are mad with delirium" trick can work.

-Bryan

[mario41051]

Hi, I have replaced the parking brake cable. I did replace also the calipers and pads.
It hold well on flat and slightly sloped road.
On my driveway (15%/20% slope?) doesn’t really hold it.

I still need to bleed well the brake. Does that affect the functioning of the parking brake also?

Thanks

[ORFORD2004]

The main reason why i change for Fiat 500 rear caliper.

[18Fiatsandcounting]

I still need to bleed well the brake. Does that affect the functioning of the parking brake also?

Not really. As Orford hinted at above, the original design is not very good, and the parking brake almost never works well.

A couple things to try: 1) Make sure that the cable adjustment is correct (4 to 5 clicks on the lever to fully lock). 2) You might try different rear brake pads. I haven't done this, but some might be more "sticky" than others. I'm thinking a softer organic pad (as opposed to the metallic or ceramic pads) might work better.

-Bryan

[mario41051]

Thank you, what I don’t understand is that i pull the parking brake when i also press the regolar foot brakes and i thought that in this way i would hold the rear brake with the same “energy” at that point once i release the foot brake. But it doesn’t really work that way…

I still need to bleed well the brake. Does that affect the functioning of the parking brake also?

Not really. As Orford hinted at above, the original design is not very good, and the parking brake almost never works well.

A couple things to try: 1) Make sure that the cable adjustment is correct (4 to 5 clicks on the lever to fully lock). 2) You might try different rear brake pads. I haven't done this, but some might be more "sticky" than others. I'm thinking a softer organic pad (as opposed to the metallic or ceramic pads) might work better.

-Bryan

[18Fiatsandcounting]

But it doesn’t really work that way…

You are right; it doesn't really work that way. But it would be nice if it did.

I never thought about it, but the parking bright *might* be slightly more effective if you press hard on the brake pedal at the same time as you pull up the handbrake lever, but I'm guessing the advantage is very slight. If at all.

-Bryan