GM Made A Pointlessly Beautiful Part That Few People Will Ever See

GM Made A Pointlessly Beautiful Part That Few People Will Ever See
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On Saturday, I took a stroll through a junkyard just for fun. In just 30 minutes I spotted some interesting hardware: A strangely beautiful GM part that few people will ever see, an awesome air intake system that cools a car’s computer, and one of the wackiest suspension designs of all time. Check it out in the first installation of my new series called “Junkyard Finds.” (Since I basically live in junkyards anyway, I may as well take you all with me.)

I am in the process of piecing together used parts for a dirt-cheap overlanding build that I plan to someday take on an expedition of epic proportions. With coil springs, front lower control arms, and shocks sourced for a total of $US50 ($65), I still needed rear control arms. A friend of mine had lifted his Jeep Wrangler JK recently, and had a set of arms sitting around, so I visited him down near Dearborn.

After handing my buddy $US20 ($26) for the parts, he and I decided to head to a local junkyard, Fox Auto Parts in Belleville, Michigan, to hang out a bit more in a socially distanced fashion. Once there, I was keen to show off my knowledge of random cars, so I kicked an early-2000s Saturn Ion’s extremely rusty rear brake drum. “What are you doing?” he asked. “Oh, I gotta show you something,” I responded. I kicked the car again. The thing wouldn’t budge, probably because southeast Michigan’s road salt was so upset that it couldn’t eat the car’s plastic exterior panels and it took it all out on that drum.

Photo: DT

Any chance at seeming cool by this point was gone. My plan to smoothly pop off the brake drum and impress my friend by showing off an obscure part had basically turned into me beating up on a rotten old Saturn. It was a bad look. But it was worth it, because I was able to enlighten my friend with this gem:

Photo: DT

I know. It’s a sight to behold. A machined, anodized aluminium wheel cylinder. In purple. It is a work of art so beautiful and moving that it nearly brought my buddy to tears.

He held it together, though, and together we contemplated: Why in the world would General Motors want to spend money to colorfully anodize an aluminium wheel cylinder that will be hidden behind a brake drum, and only ever be seen by a mechanic? Why do almost all (but not quite all) other cars use cast iron wheel cylinders? What makes this Saturn special? Surely this is aftermarket, one would think. But it isn’t.

OK, so the purple one above might be, but the factory one looks like this:

Image: Rollingautomotive (eBay), Other
Screenshot: FatGuyBuilds (YouTube), Other

It’s true. General Motors used blue anodized aluminium wheel cylinders in Saturn Ions, Pontiac Sunfires, Chevrolet Cavaliers, Chevrolet Cobalts, Chevrolet HHRs and more back in the early 2000s. These cylinders are beautiful, machined, colorfully anodized parts that one just doesn’t expect to see behind a brake drum. Normally there’s nothing here but a bunch of rusty springs covered in brake dust and a wheel cylinder made of cast iron — a brown material with a fairly rough surface finish:

Photo: DT

To figure out why GM made such a decision, and also to amuse myself by diving far too deep into a random topic that probably only 0.01 per cent of readers give a remote crap about, I reached out to an engineer who used to work for a major braking systems supplier. He broke it down for me:

Some of [GM’s] earlier forays into AL callipers ended very poorly with many corrosion failures under warranty. In an attempt to stem these issues especially with small displacement systems like a drum they chose to anodize the part for improved surface finish but also the added benefit of resistance to corrosion. Brake fluids hygroscopic tendency will rot the brake system from the inside out when owners invariably neglect the maintenance on the system. They were also trying to lower the overall mass of the vehicles at that time so though a seemingly trivial mass reduction, it would be some.

So they’re aluminium to reduce weight and corrosion concerns, and they’re anodized for improved wear (and even further corrosion resistance). Anodizing hardens the surface, so as the piston rides down the bore of the wheel cylinder, that surface won’t wear as quickly as it might if the surface were bare aluminium (which is rather soft). Thus, an anodized wheel cylinder isn’t as likely to spring a leak.

None of this explains the colour, though I guess one could just argue that it’s arbitrary. If you’re going to anodize aluminium, why choose a neutral colour if it makes no difference to the customer? Perhaps there was a real reason for the blue, or maybe that was just it: Instead of “Why blue?” perhaps the question is “Why not?”

Update: The engineer who used to work for a major automotive brake supplier provided me with more information on how anodizing reduces wear. He also provides a possible reason for why the wheel cylinders are blue; it has to do with the production process:

Wear and “knockback” go into the surface finish requirements. As shoes wear the retraction force generated by the springs due to corrosion and binding will go down. A finer finish on the ID will produce less seal drag and allow the small pistons return reliably. The square packings in a caliper will provide this same effect, so the surface finish requirement is less on callipers generally because the packing shears so to speak, changing from a square packing to a parallelogram and once the pressure is released it’ll relax back to a square.

It is true that they do have colourless anodizing, however, knowing UAW workers and suppliers, it becomes a big issue of knowing IF all operations have been completed on a part. Blue colour was crime of opportunity to just say with a giant red flag definitively, YES, this is coated. if it were colourless they wouldn’t know at a glance if it was done or if it missed the op. Generally this sort of thing isn’t done at the primary machining place so a secondary supplier would do and it’ll need logistics and errorproofing. The need for the anodizing is a wear / corrosion proofing need. The anodizing is considerably harder than a raw 356 cast part, and on top of that, it’ll prevent the first mentioned corrosion issue. over time the seals would wear into an unfinished bore. (we had this problem for a durability concern in our ABS valves in the past for the ABS pump motor bores)

The video above shows me dismantling a wheel cylinder and describing how it works using the cylinder from my Chrysler Voyager. Notice how hideous that cast iron piece is compared to this:

Image: Competitive-Automotive (eBay), Other

OK, so enough about a blue wheel cylinder. I’ll also point out another fun bit of tech that I saw in the junkyard. This is something that I learned while working on my 1994 Chrysler Voyager diesel: In the 1980s and 1990s, Chrysler used to cool its engine computers using the vehicle’s air intakes:

Image: DT

It makes sense. The intake is positioned to pull cold air from near the grille or behind the headlight (engines are more efficient when the intake air is cold). And though using the air to cool the ECU will lead to an increased air charge temperature for the engine’s intake flow, I’m going to guess that the heat pickup from the computer was rather small, and engine performance degradation is probably negligible.

Apparently such a setup isn’t as uncommon as I thought, as Twitter-izer Matthew Dear showed me that even modern BMWs apparently cool their computers with intake air, as shown above.

Photo: DT

The final thing I’d like to show in the first instalment of this new “Junkyard Finds” series is a Ford Ranger’s Twin Traction Beam front suspension, a setup used exclusively on Ford trucks for decades. The suspension includes two “long arms” spanning from a frame crossmember to the steering knuckles; two radius arms hooked up to another crossmember and reaching forward to those long arms; and axle shafts that reach from the differential, through the long arms, and to the wheel hubs.

I’ve written all about how “TTB” works in my story about Ford Ranger suspensions over the years, so check that out for more info, though if you just want a quick peek at how the suspension works in practice, behold this glorious .gif:

Screenshot: William Dick/YouTube, Other

That’s all I have to share today from my short junkyard stroll. Expect more soon; I have a suspicion that millions of Jeep Cherokees were manufactured with an egregious spelling mistake on a major vehicle component. I’ll be searching for XJs to confirm and will report back.

Update (Jan 12, 2021 9 A.M. ET): This story has been updated with additional information for an engineer who used to work for an automotive brake parts supplier.