Rear calipers e brake

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tima01887
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Rear calipers e brake

Post by tima01887 » Mon Sep 02, 2019 10:32 am

Comparing my new calipers to old, When i actuate the lever on the old caliper the piston screws out. On the new caliper it doesnt, Seems like that is why my e brake only works once. Any suggestions on the new ones? Should I just eat the year old calipers and buy from a different vendor? The only difference between new and old is the dia, of piston and the hose fittings are not spot faced. Any help is appreciateed
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18Fiatsandcounting
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Re: Rear calipers e brake

Post by 18Fiatsandcounting » Mon Sep 02, 2019 12:33 pm

I guess I have more questions than answers at this point, but my initial guess is that the self adjusting mechanism inside the piston isn't "adjusting" as it should. When working properly, the "nut" inside the piston rotates as it slowly works its way down the threaded shaft of the plunger rod, allowing the piston to move out as the brake pads wear yet still provide the few millimeters of outward motion when you actuate the emergency brake. Note that the Belleville washers (5 of them plus one flat washer) must be installed so that they aren't "spooned" against each other. Putting the rear caliper back together with these washers properly oriented can be a royal pain, but it's necessary for the whole thing to work properly.

Questions: When you say the piston "screwed out" on the old calipers when you actuated the emergency brake lever, do you mean that the piston simply "extruded" outward, or did you mean that the piston actually rotated in the caliper as it was driven outward? The former is how it should function, but if the latter is happening, something isn't right in the self-adjustment mechanism inside the piston.

On the new caliper, are you reusing the old piston, or a new one? Are you reusing the old mechanism inside the piston, or is it also new? In either case, is the nut properly installed with its spring, and the retaining plate and circlip are properly installed?

If you search this forum, you'll find advice on assembling these, and probably some useful diagrams if you don't already have them. Other posters will no doubt offer some good advice.

-Bryan
tima01887
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Re: Rear calipers e brake

Post by tima01887 » Mon Sep 02, 2019 12:44 pm

These are new calipers, The calipers of old push the caliper in twards the pad as i acuate the lever, The new ones do not. I took the new caliper apart and the Bellville washers were not as diagramed, So I put them right. Like you say a real PIA, But after all that the piston still does not push to the pad side when actuating the e brake lever. Too much work, The new calipers should just function properly, When I say screwed in that is the function of the e brake being independent of the hydralics, Safety issue here.
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miker
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Re: Rear calipers e brake

Post by miker » Mon Sep 02, 2019 1:38 pm

Really new, or rebuilt? If new, who was the vendor?
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tima01887
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Re: Rear calipers e brake

Post by tima01887 » Mon Sep 02, 2019 4:00 pm

Rather not say who the vendor is, But one of our vendors. Sold as new and they look new not a fiat casting mark. My question is whith the caliper on the bench, actuating the lever, should the piston move forward until the piston is fully extended?
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18Fiatsandcounting
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Re: Rear calipers e brake

Post by 18Fiatsandcounting » Mon Sep 02, 2019 4:15 pm

tima01887 wrote:
Mon Sep 02, 2019 12:44 pm
But after all that the piston still does not push to the pad side when actuating the e brake lever.
When you say "e brake lever", do you mean the handbrake lever in the center console inside the car, or the 2 inch or so lever on the rear brake caliper? If it is the handbrake lever inside the car that isn't operating the emergency brakes, a common reason is that the emergency brake cable is broken, operating on only one side, or not adjusted properly.

If you operate the 2 inch or so lever on the rear calipers and the piston doesn't move at all, it could be that the piston is not inserted all the way into the caliper bore, or the self adjustment mechanism has something wrong with it (other than the Belleville washers which you checked).

-Bryan
tima01887
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Re: Rear calipers e brake

Post by tima01887 » Mon Sep 02, 2019 4:18 pm

So yes, off the car on a bench. Should moving that lever screw the piston in with every thrust? The old calipers move the pison with in with each thrust movement until the piston is all the way out.
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18Fiatsandcounting
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Re: Rear calipers e brake

Post by 18Fiatsandcounting » Mon Sep 02, 2019 7:20 pm

Something seems odd. With the rear calipers that I've worked on, moving the lever arm on the caliper moved the piston outward a couple millimeters, but when you released the lever arm, the piston moved back to its original position. The piston did not ratchet outward with each operation of the lever.

While in the car, operating the hydraulic action of the rear brakes will push the pads up against the rotor, while at the time the nut inside the piston slowly screws its way down the threaded actuator rod of the emergency brake as the pads wear, so that the emergency brake actuator is always at the right position for the emergency brake to work.

With a properly operating emergency brake, yanking up the emergency brake lever in the car should lock the rear wheels. Of course, we have to help you get to that point! 8-)

-Bryan
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Re: Rear calipers e brake

Post by bartigue » Mon Sep 02, 2019 7:48 pm

Timothy,

Post a picture of these calipers please. They do not sound like the correct part in description or operation, but even your description of the old calipers sounds wrong.

The caliper piston moves outward by hydraulic or mechanical pressure; hydraulic from the hose, mechanical from the lever arm. The mechanical action works again a threaded rod. Inside the piston is a device that allows the piston the maintain the same distance regardless of pad wear.
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tima01887
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Re: Rear calipers e brake

Post by tima01887 » Tue Sep 03, 2019 6:11 am

Brad,
The calipers are as you describe, I dont think a picture would help much. My attempts at description are lousy but I am trying. No load on the caliper, No pad sand off the car. No hydraulics just acting on the e-brake lever piston installed, Should that move the piston to a maximum travel., or just back and forth a 1/4 inch or so with no forward movement?
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