36 votes
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what is round cylinder on top of classic car engine

You're talking about a classic air filter housing. Older style air filters were round in shape and sat inside a round metal enclosure. This is a Holden straight 6 from the 80s, where the air filter ...
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  • 1,086
21 votes
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What is the purpose of this black plastic loop around rim spokes?

The wheel trim that it is holding on is likely damaged, so a previous owner has added the cable/zip tie to stop it falling off. The damage may not be visible from the outside. There are plastic tabs ...
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  • 20.9k
13 votes
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What is this thing hanging from a wire from the front headliner at the top of the windshield?

Figured out it (thanks to a shove in the right direction by @mikes): It's the remote engine start accessory's antenna. I didn't think of it when I was asked if I had "add-ons" because it's an ...
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  • 491
11 votes
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What is the small plastic dimple found on some front doors?

It is a guide for the window as it closes. It is only needed for closing the window when traveling at higher speeds as the airflow sucks the window outward. Why you see it on cheaper cars probably has ...
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10 votes
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Front left controller arm corroded and broke on my 2002 Hyundai Elantra

You have severe case of corrosion. The part is called the lower control arm. Its function is to maintain the tire in the correct position. Do not attempt to drive the vehicle. In the best case ...
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  • 19.7k
10 votes
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Purpose of highlighted mirrors in trucks

They provide the driver with coverage of two significant blind spots. Especially in cities, there are numerous accidents with cyclists, pedestrians or even small cars being in that blind spot and ...
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  • 18.5k
10 votes
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What is this box next to my car's battery?

That is your diagnostic connector. You will need a Mercedes-specific tool to read trouble codes stored by the computer.
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  • 12.1k
9 votes

What's this part? Hanging from left rear of Subaru 99 legacy.

It's the EVAP vent solenoid. And I think you mean right rear.
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  • 10.7k
9 votes
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Discerning a component of a motorcycle

According to this https://www.yamahamotorcyclespares.co.uk/genuineparts/13208/8/yamaha%20xj6n/oil%20cleaner?uid=0 parts manual (image not copied to protect copyright) its the oil cooler assembly. ...
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  • 2,645
8 votes
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What is this (cooling-system related) part?

This is the heater valve. It's Motocraft part# YG350:
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8 votes

Which 18-pin automotive connector is this?

It seems that this is one of Delphi's own proprietary connectors - it's not a Tyco one. From a cursory search, the mating connector appears to be "Delphi 13658062". However there is no datasheet for ...
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8 votes
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What is this U shaped tube sticking off the intake hose?

It's a silencer. It's used on the intake tract to deaden the noise of the air as it goes through the intake. It usually isn't needed, but if taken off, you'll need to ensure the hole is completely ...
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8 votes
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What is the name for the spoiler above the cabin of a semi?

It's most typically called a wind deflector. You can see it listed as such on this website. It can also be called a cab air deflector or even an air foil.
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8 votes

What is the name for the spoiler above the cabin of a semi?

That part is known as either a wind deflector or a Roof Fairing. I believe the latter is the correct technical term. To satisfy your curiosity about the other parts as well. I know it is a little ...
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  • 3,842
8 votes
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This part fell from my car when driving - any idea what it is?

2nd that; its a catalytic heat shield. Now your catalytic convertor will be able to ignite grass fires when parked more easily.
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7 votes

What is a "confidential vehicle identification" number?

A confidential vehicle identification is just a VIN in a hidden place that is only known by the manufacturer and law enforcement. It is used to thwart car cloning. Examples of this would be a VIN ...
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  • 1,965
7 votes

Missing part on '87 Ninja 600R

There is a hose that connects your air box to this As stated in comments, this is connection point for a PCV hose. The hose connects to the bottom of your air box that attaches to your carburetors. ...
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  • 32.8k
7 votes

Coolant Flange - What is it really called?

tl;dr: it's really called a coolant flange. I had also never heard of a coolant flange but it turns out that it's a real part and, based on the video, it's a part that fails around 120K miles (which ...
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  • 24.3k
7 votes
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What is the difference between an inner tail light assembly and an outer tail light assembly?

The tail lights on this car look like: (image source) The outer assembly is the one on the quarter panel: The inner assembly is the one on the trunk: I'm 99% sure of this, but note that it is the ...
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  • 4,910
7 votes

why does the VW dealers in NA have a different battery than OEM?

When I worked for BMW NA, I was the 'Merican engineer responsible for batteries, start, and charging systems on BMW vehicles stateside from about 1990-95. There was some bean-counter thing that also ...
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  • 12.2k
7 votes

Do month-year coloured dots on batteries signify install-by expiration date?

No, these are not sell-by dates or expiration dates. If batteries expired within a couple of months of manufacture, they'd be useless for their intended purpose. Getting a battery that's been ...
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  • 1,536
7 votes

Do month-year coloured dots on batteries signify install-by expiration date?

The "9/16" marker (at Walmart, at least) is the nominal date of manufacture - the actual date may be a few weeks earlier. It's used for warranty replacements. Walmart batteries are often on a 3+2 ...
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  • 8,612
6 votes
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What is this lever?

I'm not positive, but it looks like a vent actuator. In most older vehicles there were manual vents down in the foot well area of the passenger cabin. You'd have to reach down to actuate it by pulling/...
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6 votes

What is this part?

I'd need exact details to confirm, but this should put you on the right track: "Stopper, rear" This genuine part fits your 2007 BMW 1 Series (E82,E88) 135i. Stock Code 33316794866 ; 33316763411 ...
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  • 12.2k
6 votes
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Small black box located under intake manifold

It's a vacuum canister, it holds vacuum so the EGR can operate smoothly. Video of a guy talking us through the Subie's intake on his workbench Video of the same guy talking us through the Subie's ...
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  • 12.1k
6 votes

What is this object

It's a damper, probably from a glove box door. Does your glove box open and close smoothly with a little resistance? Or does it just plop open when you pull the handle? If it plops open, that part is ...
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  • 1,124
6 votes

What is the purpose of this black plastic loop around rim spokes?

These cable ties are usually found on the cheaper plastic wheel trims as they can fly off. Some of the more expensive ones suffer from the springs and tabs getting bent when owners force them. Seen ...
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  • 34.4k
5 votes

What is this (cooling-system related) part?

This is your Heater Control Valve But I am going to explain what it does. First of all the "wire" you see is actually a vacuum line, it's a hollow (hopefully) air-tight tube that passes vacuum to the ...
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  • 197

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