Apropos Tech Solutions Corp. Blog

Category: autos

  • Autos: replacing brake pads: cleaning the carrier

    Changing brake pads, mechanics say to clean the carrier. Why is that so important?

    The following is by my understanding.

    Brake pads are a wearing surface: they are meant to wear out and be replaced. Calipers, however, are not. When one needs to replace brake pads, one hopes not to have to replace the caliper as well, since it makes the job more expensive.

    Calipers, as I understand, wear out because of heat: because, in particular, the brake pads aren’t moving in and out like they should be. One reason for that can be jammed caliper pin(s), from insufficient lubrication. (Needless to say, when replacing brake pads, the caliper pins and their housings, including the boots, need to be cleaned and regreased.)

    However, another reason the brakes might not be opening and closing freely can be that the pads themselves aren’t moving well on the tins – those metal liners between the carrier and the ears of the pad.

    One reason the pad can become sticky against the tin is that dirt and corrosion have gotten behind the tin, between it and the carrier body, effectively pushing the tin inward against the ears of the pad. Hence, as I understand it, the reason to clean up the carrier, then grease where the tins will go: so corrosion won’t start there.

    Therefore, to protect the caliper, one must clean and maintain the carrier: that’s why mechanics emphasize cleaning up and regreasing the carrier when replacing brake pads.

    Source:

    TRQ. (May 20, 2025). “How to Replace Front Brakes 2007-2017 Jeep Patriot 2.4L L4.” [Video]. YouTube. https://www.youtube.com/watch?v=y-5gU6DTpZw

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  • Autos: caliper pins

    Replacing brake pads, one faces brake calipers. In particular, their pins seem to demand attention, regarding their removal and even which is which.

    The following is by my understanding.

    I mention in my post from Sept 26 using penetrating fluid to loosen caliper bolts. On the vehicle I’ve been working on lately, a 2013 Jeep Patriot, the caliper bolts and caliper pins are the same thing.

    A peculiarity of this vehicle is that the two pins of a caliper are different. Specifically, one has a rubber bushing while the other doesn’t. Which is which, and why?

    It turns out that if one caliper pin has a rubber bushing, it’s usually what they call the trailing one, meaning the second one a point on the rotor would pass during a revolution of the wheel. The rubber bushing is meant to prevent vibration, noise, etc. It seems to work pretty well, in that regard.

    Yet, the rubber bushing can make the trailing caliper pin very hard to extract. I’ve been in a situation where the caliper pin was unscrewed past the threads, would turn freely, but just didn’t want to come out. Putting a wrench around the underside of the bolt head can facilitate more effective pulling, but even then it can be surprisingly hard to remove.

    Source:

    ScrewsNutsAndBolts. (Nov 22, 2024). “Brake Caliper Slide Pin Rubber Bushing – Top or Bottom?” [Video]. YouTube. https://www.youtube.com/watch?v=NfMLBOd5Ox0

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  • Hardware: how long for penetrating oil to work?

    Sometimes it seems like a stuck bolt might never come loose. How long is reasonable to wait, after applying penetrating fluid, before trying?

    Yesterday I was working on the brakes of a vehicle. Knowing that soon enough I’d have to replace the pads, I decided to loosen the caliper bolts, then tighten them back up. That way, when I would have to undo them next time, they (hopefully) wouldn’t be so hard to get loose.

    In my experience, caliper bolts can be really tough to loosen. Yesterday I did manage to get each one loose, with some struggle.

    A tried-and-true method, it seems, is to apply penetrating fluid to the stuck bolt, then wait before trying to loosen it. Yet, how long should one wait?

    Apparently, a few hours to overnight can perhaps be reasonable to wait for penetrating fluid’s full effect.

    Yesterday, I waited five to ten minutes. Did I end up working too hard simply from my lack of patience? I guess it’s something to think about, going forward:)

    Source:

    Spaans, Jacob. (Apr. 19, 2019). “Use Penetrating Oil to Loosen a Stuck Nut or Bolt.” https://winworks.com/use-penetrating-oil-to-loosen-a-stuck-nut-or-bolt/

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  • Autos: change oil indicator light reset, Dodge Grand Caravan 2016

    When you change your own oil, the “change oil” indicator light might come on at an unexpected time. Why, and how to reset it?

    The following is by my understanding.

    About every six months, I change the oil for both vehicles in this household.

    A couple of days back, the “change oil” indicator light came on when my wife started the van (2016 Dodge Grand Caravan). I knew I’d changed its oil in early July, so wasn’t worried.

    With the 2016 Dodge Grand Caravan, the “change oil” indicator light comes on according to a cumulative measurement of duty. When you change the oil, the computer system can’t tell. It just continues monitoring how much work the car has done since its last reset, and eventually reminds you to change the oil.

    To reset the “change oil” indicator on said vehicle, one follows these instructions:

    1. Turn the ignition to on/run, but don’t start the vehicle.
    2. Within 10 seconds, press the accelerator pedal down, then let it return, three times.
    3. Turn the ignition to off.

    Source:

    2016 Grand Caravan User Guide

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  • Autos: tire pressure and load, part 0

    Does tire pressure increase when you put more weight on the tire? There are conflicting ideas…

    I’ve been looking around the Internet. Some people suggest adding weight to a vehicle will increase its tire pressure; some say it won’t.

    I’m of the opinion that added weight won’t increase a vehicle’s tire pressure, by the following reasoning. At a fixed temperature, PV=k, that is, pressure multiplied by volume is constant for a confined gas.

    Given PV=k (assuming fixed temperature), the only way for pressure to increase is if volume decreases. Yet, it seems unlikely to me that a tire will shrink as more weight is put on it. The tire can bulge out the sides, for instance, to make up for a decrease in height.

    I plan to revisit this topic, but that’s my idea so far.

    Source:

    White, J.E. (1987). Physical Chemistry. Books for Professionals, Harcourt Brace Jovanovich.

    Grassroots Motorsports. (2018). “Tire Pressure: Hoist vs On the Ground.” https://grassrootsmotorsports.com/forum/grm/tire-pressure-hoist-vs-on-the-ground/3231/page1/

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  • Autos: how much torque to turn healthy engine?

    The idea of how much torque is required for tasks in mechanics can be fascinating.

    The following is by my understanding.

    In my previous post I mention the idea of drive size, torque, etc. Ideas of aligning drive size with socket size, as well as torque requirements of certain tasks, naturally arise thence.

    The idea of turning over a car engine, by hand, is one I’ve been hearing about lately. One wonders what torque that might require.

    It turns out, apparently, that it might only take around 20 ft*lbs of torque to crank over a healthy engine by hand. Such can be done, at least in some cases, using a 1/2″ drive torque wrench.

    Source:

    YouTube: MotorCarNut: “How To Tell If Your Engine Is Seized”

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  • Autos, hardware: drive size for sockets

    Most people might be familiar with a basic socket set. Yet, drive size might be less obvious.

    The following is by my understanding.

    I recall buying a socket one time to remove the anode of a hot water heater. It was, I think, one-and-one-sixteenth. I bought it from a discount bin, and it came on a straight bar. I was in a hurry, so didn’t think much of it.

    Later, I had to buy a 15/16″ socket to undo an oil filter casing. The clerk asked me what drive I was using. I didn’t know. The socket was 1/2″ drive. He assumed, correctly, that I would need an adapter from 3/8″ drive to 1/2″.

    Back then, I just had a standard socket set from Mastercraft. It had both 1/4″ and 3/8″ drives, and its largest socket was 3/4″. It hadn’t occurred to me that bigger drives – for instance, 1/2″, were called for sometimes. However, when I got home from buying the 15/16″ socket, I inspected the one-and-one-sixteenth socket, on its bar, that I’d bought years ago to remove the water heater anode. Indeed, that socket, too, was 1/2″ drive.

    When I thought about it, the reasoning was obvious why 1/2″ drive might be called for: a bigger fastener might well mean it’s under more strain, so needs to be tighter. In turn, a larger-diameter drive would be stronger, so less likely to break when removing such a fastener.

    It turns out that, for 3/8″ drive, the torque range tops out around 75 ft*lbs, then for 1/2″, around 250 ft*lbs.

    It’s hard to imagine me, personally, applying more than 250 ft*lbs of torque, but apparently that’s when 3/4″ drive becomes relevant.

    Source:

    eTork. (Sept 4, 2024). “Torque Wrench Sizes Explained.” https://etork.com/torque-wrench-sizes/

    -js

  • Autos: transfer case

    With a 4WD vehicle, one might hear about the transfer case. What is a transfer case, and what does it do?

    The following is by my understanding.

    A couple of lifetimes ago, I took a heavy-duty pre-app course, ten months. Until then, I’d spent my life in the academic world. I learned a great deal in that heavy-duty pre-app program.

    Yet, from any course one takes, there might be leftovers – things one didn’t quite catch, but partially recalls. For me, one topic from the heavy-duty pre-app course was transfer cases.

    A transfer case conveys power to the end of the vehicle where it’s optional. Therefore, a typical 2WD vehicle wouldn’t have a transfer case, but just an engine, transmission, then differential.

    With a 4WD, the transfer case contains what one might call a pressure plate that turns with the output shaft to the permanent driving axle. The optional driving axle, via a clutch (that’s what I’d call it), can be shifted into contact with said pressure plate. Then, 4WD mode is accomplished.

    The fact that it’s a clutch-type connection that actuates 4WD explains to me why, on the vehicles I’m familiar with, one can launch into 4WD while already driving.

    Source:

    YouTube: Engineering Explained (May 2, 2012). “Transfer Case – Explained.” https://www.youtube.com/watch?v=K1qj8dHTmP4&t=1s

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  • Autos: 10w30

    10w30 motor oil was common when I was a kid. Why does it seem not so anymore?

    The following is by my understanding.

    When I was a kid I had a Honda 50 minibike. My understanding was that it took 10w40 motor oil. I knew some people who interpreted the manual a different way, so used 10w30 with theirs. “That means it acts like 10 weight when it’s cold, but 30 weight when it’s hot,” somebody said. Even at age 11, with no hands-on experience with engines, it made sense to me.

    Decades later, I drove a (used) sedan that took 10w30 oil. I recall hearing 10w30 mentioned a lot by car people, in connection with their used 70s and 80s cars.

    Nowadays, the lawn mower I use takes 10w30, but the vehicles we drive, both from the 20-teens, take 5w20. Sometimes I wonder what happened to 10w30, vehicle-wise.

    I have realized for awhile that thinner oils go along with smaller tolerances, so the oil can get into the smaller spaces.

    Yet, another idea I wasn’t thinking of is that a thicker oil is harder for the engine to circulate. Therefore, another reason manufacturers are going to thinner oil is to ease its motion throughout the engine.

    Interesting, eh?

    Source:

    classichonda50saustralia.com.au

    Jiffy lube of Indiana (Feb 15, 2021). “The Evolution of Motor Oil: Why 10W30 Is No Longer the Most Popular Choice.” https://jiffylubeindiana.com/vehicle-maintenance/the-evolution-of-motor-oil-why-10w30-is-no-longer-the-most-popular-choice

    -js