Question of the Week: What’s the dumbest mistake you’ve made working on your car?


I have learned so many things over the years doing some things the hard way till I got older and wiser.
I was a shade tree mechanic in the 70’s. In the early 80’s I took in many jobs because I could work on almost anything and any problem domestic or foreign. In the late 80’s-early 90’s I ran a station and also worked as one of it’s mechanics leaving to eventually become a lead millwright at a factory. Although I had done some crazy or downright unsafe things throughout those years it never cost me more than a busted knuckle, cuts, metal splinter, burns or what have you. I was smart when I needed to be and lucky when I was not. I feel so bad for your experiences because when you did not take proper precautions you received the worst possible outcome every time. I think any of us can relate and have empathy for you because if not by the grace of god any of us who are mechanically inclined could have experienced the same results. When alive my dad used to tell me, " God protects babies and fools and you are too old to be a baby ". I am sorry someone whom we can all feel a kinship to has had to endure the injuries that could have just as easily befallen any of us.


Not me. A friend of mine of course. In refilling an oil change allowed the little plastic lock ring from the oil quart to fall in and get washed deep. He was unsure but decided it might “pass” like the puppy that eats a quarter. That, 20 years ago but those tabs are still on a quart so we can learn something.


I was 16 had a 65 Austin Healy Sprite. I rebuilt the motor and forgot to put the clamp on the oil pressure gauge. ran great for about 5 min.oil gauge line came off, 4 quarts of oil spewed out,smoke every where .Rods rattleling . To top it off i failed to put the hood latch secondary catch on. The wind blue the hood up.I fixed what i could and still drove the car, never told my dad ,he came my the $40 for rings and bearings

  1. I somehow managed to put brake pads in the caliper friction side out. No clue how I did this but I’m sure it will come up as a story at my funeral! 2. Filled the engine with oil while the drain plug sat on the workbench.


I was around 17 in the mid-80’s doing something under the hood of my first car, a straight six 64 1/2 Mustang coupe, engine running, when somehow I got hold of a plug wire or the coil wire. Don’t recall which. Of course the current makes you tense up, grabbing tighter onto the wire. I recall the power going up one arm and down the other. Been paranoid about electrical ever since.


Always parked my Audi TT on carpet remnants to prevent “hot tire” damage to my recently painted garage floor. I used the factory jack to remove rear wheels and replace rear pads. Carpet allowed car to slide sideways and the jack to crunch into side of car. After repair at the body shop I purchased a floor jack.


I’m getting older and need reading glasses. About 4 months ago I was too lazy to find them. As a result, I misread the torque setting as “ft-lbs” not “inch-lbs” and proceeded to strip out a bolt in a BMW aluminum block for the oil filter housing… this turned out to be VERY expensive and time-consuming mistake… proving you’re never too old to be stupid.


Ha Ha…favorite trick at the race track when messing with your friends!


@robert - I love my inch-pound torque wrench, when I remember to use it. Which is never often enough.


I learned the hard way it is possible to put heads on a Pontiac 400 on the wrong side. Didn’t figure it out until the valves were set and headers were torqued. Intake wouldn’t fit. Duh


@dray4422 - Now that is one I have never heard before!


It was my first time. They were off awhile during my project. Corrected the mistake in about 6 hours


After I graduated high school I pursued an associate degree at the automotive tech department of a technical trade school across town from where I lived. Most of my class consisted of a bunch of 19 year olds peppered with a couple older guys brushing up on their skills or pursuing a promotion. One day a couple of my young classmates and I replaced a master cylinder on one of the classmate’s mom’s '74 six banger Matador (a car I had covertly raced in my mom’s '70 slant six Dart). When we were all finished bleeding the brakes the guy whose mom owned the car told us to go take it out for a test drive. “Dog it up” he said. So we did. The other guy and I took turns doing crazy maneuvers around the neighborhood trying to get it to fishtail, do burn outs and four wheel lock ups. We were working that white four-door Matador like Roscoe P. Coltrane. The brake warning light came on a couple of times but the brakes seemed to be working just fine with a normal firmness and pedal height. When we got back to the shop I was driving. I pulled up to the bay door and stopped quite abruptly with a chirp of a tire. When I pulled into the bay however and pressed the pedal it gave absolutely no resistance. It went straight to the floor without warning or giving any resistance to the vehicle’s forward motion and we rolled straight into the steel work bench the brake lathe was mounted on, crushing it into the cinder block wall. The instructor came over and backed the car out while we looked on sheepishly and, of course, the brake pedal had returned to its normal high and firm character. I tried to explain what had happened to one of the most patient teachers I have ever known and, although he remained calm, the look he gave me conveyed quite clearly that he thought my story was pure BS. He had seen me drive up to the building after all. Thankfully no real harm was done. The monstrous front bumper on the car protected it from virtually any damage save for four small slats knocked out of the grill. The lathe itself was unharmed and we spent most of the next two days hammering out and trying to realign the 14 gauge, or so, panels of the workbench while the rest of the class learned the fine points of reading a ‘Sun’ machine. We were totally baffled about how a master cylinder could so completely fail then immediately return to normal operation but the guy whose mom owned the car said it happened again on at least one other occasion. I think they eventually took it to a repair shop and had the job redone.


Easy. In some cases, actually starting a project was the mistake…

And countless times, the doodad that is supposed to go on the left, ends up on the right. And vice versa. Of course, I notice this fact as I’m tidying up the tools. (much swearing ensues) then, time to undo my stupidity.


Replacing the valve cover gasket on my '02 BMW 325 and I broke one of the hoses for the PCV assembly, which on that car replacement requires either baby hands (I’m 6’2 240 and can palm a basketball, that’s not my situation…) or near complete disassembly of entire intake system. A 2 hour, $60 job turned into a 2 day, $500 job… I feel like this belongs on FML.


Learned from this mistake at an early age. Don’t pull all the spark wires all at once.You may think you can. Remember which wire goes to the right plug. Wrong. You can only replace one plug at a time. So, why not do plu wire at a time.


Put a clutch disc in backwards on a 1960 Chevrolet while laying on the ground coldest day ever I worked on a car 10 degrees.


Bought a Buick Grand National from a guy who told me the head gaskets blew and he put it in his shed & it sat for years. So I bought it cheap knowing I could replace the gaskets myself. So I get it home & start it for just a minute & its blowing white smoke like mad!
So I start tearing it apart. I get the right head off & I cant see any sign of coolant or gasket failure. Same with the left side. Humm.
I’m new to the turbo game as I was a Chevrolet dealer tech for 18 years. So at the time, the internet was just gaining speed & not too many forums yet.
But the one I found had an area for questions from newbies like me. It wasn’t an hour after posting my problem an experienced poster told me it probably was my internal turbo seal. He told me to replace or throughly clean the intercooler. While the engine was apart I had the valves done & I replaced the cam & lifters, oil pump, etc. When I started the engine the smoke was gone.


Ex-crew screwing self-centering lug nuts on backwards.


In the course of detailing the engine bay on my 1964 Corvair Coupe, I disconnected all of the spark plug wires.
I did not take note of where plug wire “1” went on the distributor.
This led to a confusing afternoon of back firing, and eventually the Muffler exploded!
Being 17, I though a blew up the motor!
I knew the firing order was stamped on the motor but,
at this time nobody was on youtube guiding us like they are today and I had to sift through poorly pixelated pictures from EBAY MOTORS sales ads to find a photo with the correct order. Pro tip: Always take pictures before disassembly