Alfa Romeo brake system overhaul, Part 2

As you read in Part 1 of the Alfa Romeo brake system overhaul, the new front calipers I had purchased, through no one’s fault, didn’t get the job done. It was just as well; in an attempt to get my car ready to drive to the AROC Convention in Pittsburgh, I was hurrying through the job, which is no way to work on a braking system. If anything, the inability to make the car roadworthy gave me just the excuse I needed to do the right thing.

 

I had purchased this car in 2013 from my friend Pete. He bought it in 1968, drove it for perhaps five years, mothballed it for over 20 years, then took it out of long-term storage. After refreshing various systems, including the brakes, Pete enjoyed the car for about 10 years before handing over the keys. In my mind, this Alfa had been “recently” refurbished. However, once I added up the years and the miles, I realized my own miscalculation. At best, Pete worked on the brakes around the year 2003, meaning, the brake fluid alone was now 16 years old. Shame on me! Since I loved driving the car, I wanted 100% confidence in its brakes, so The Right Thing meant a complete overhaul: rebuilt calipers, new or rebuilt master cylinder, and new lines and hoses. I got all 4 wheels up off the ground, drained what little fluid remained, and brought both front calipers to the workbench.

Caliper with piston, dust boot and spring in place before removal

First, the dust boots and their retaining springs had to be removed. The springs were so rusty that it was difficult to see them against the boots, but with a little urging from a dental pick, they popped off. The boot for the seized piston looked like it had been on fire (it almost was), and this early discovery reinforced that this overhaul was necessary and overdue.

 

Dust boot and rusty old spring on their way off

 

This dust boot is ready for the trash can

 

I’ve rebuilt calipers before, as a Volvo tech, but it wasn’t a job we did very frequently. All 4 of my car’s calipers are of the two-piston fixed type, and research from my Alfa library led me to conclude that there was no need to split the calipers. The pistons could be removed with compressed air, and the bores cleaned up as necessary.

 

This 2-piston caliper has 1 piston behind each pad. It is “fixed”: the two halves are bolted together.

Starting with the seized right front unit, my technique was to start by pushing the pistons back into their bores with a piston compression tool. The reasoning is that any movement is good movement. Once they were fully retracted, I hit the fluid passage with compressed air, and both pistons moved outward a few millimeters. The cycle was repeated: retract pistons, apply air; retract pistons, apply air. Finally, one piston popped free.

At the start, piston retraction tool was used to push pistons all the way back

 

Compressed air is good stuff

 

But now I had a problem: the compressed air escaped from the now-empty bore, and did nothing to move the piston still in place. I reinstalled the removed piston, but the same thing happened: one piston came out, and one stayed in. I needed a way to block the fluid passages without fully reinstalling the first piston. Stuffing rags into the bore did nothing.

C-clamp is employed to hold 1st piston while compressed air dislodges 2nd one

Here’s how I did that: lubing up the piston with brake fluid, I reinserted it just a few millimeters back into its bore, enough to block air flow, but not so much that I couldn’t pull it out by hand. I held this piston in place with a C-clamp, so the force of the air would blow out the 2nd piston. It worked! The 2nd piston shot out, and once I removed the C-clamp, the 1st piston could be worked out with my fingers. With the pistons out, the inner seals were easily coaxed out with a dental pick.

Removal of the inner seal

A close examination of the pistons revealed that one had a mark along its surface. My local Ace Hardware store had 3M brand emery cloth which I bought in medium, fine, and super fine grit. While I couldn’t completely remove the nick, I smoothed it out so that it couldn’t be felt. The front lips of the pistons showed marks from pliers or Vice-Grips, so someone (not me) got aggressive with a prior piston removal attempt. Thankfully, the marks would not affect the braking performance.

The bores themselves showed some minor corrosion along the outer edges, but the insides (below the inner seals) weren’t bad, and the super-fine emery cloth made them even better. While this was going on, the rear calipers were unbolted and disassembled so that I could measure the piston diameter. According to my supplier, Classic Alfa, this generation Giulia used either 30mm or 36mm rear pistons, and of course, one needed to know before ordering parts. It turned out that my car has 30mm pistons. I placed my order with my favorite Alfa supplier, knowing that I’d have the parts within 48 hours or so.

 

 

Pistons before (left) and after (right) emery cloth treatment

 

Nick in surface could not be removed, but was minimized. Note pliers marks.

 

Rear caliper piston confirmed as 30mm

 

… to be continued …

 

All photographs copyright © 2019 Richard A. Reina. Photos may not be copied or reproduced without express written permission.

 

 

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