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


I have been doing my own work for 53 years, so I have made lots of dumb mistakes. Here are just 2:
I don’t use my 99 Volvo wagon much anymore, so I often put the charger on the battery to keep it alive. One night, I needed the wagon, so I went into the garage, opened the middle door and, walking in the dim light, closed the hood of the Volvo, got in, and backed out. Hmmm. What’s that slight scraping noise? Moving forward, no more scraping noise, but a thump as I run over something. I get out of the car an find the flattest battery charger on planet Earth. The scraping noise was dragging the still connected charger out of the garage.

Back in 2007, I was doing the first oil change on my wife’s new Infiniti M35. I had just moved the pan of old oil to someplace where I wouldn’t trip over it, when my then 16 year old daughter came out the remind me that I was supposed to drive her someplace. “Yeah, yeah. Just give me 5 minutes…” I get in the car, start it up and look underneath to check for leaks…no leaks. Shut off the engine and start to walk into the garage and just stop dead when I see the unopened case of new oil in front of the car. With the distraction, I had forgotten to put oil back into the motor. I had visions of a $10,000 bill to replace an engine with 3,500 miles on it, but there must have been enough oil on the bearings from running the engine just before the oil change, because 100,000 miles later the engine is still running fine. Dodged that bullet.


Have 2 good ones from when I was 17 years old.
I had a 1962 Chrsyler Newport 4 door sedan with a 361& factory 3 speed stick.Yeah you read it right, a factory 3 speed stick.
I bought a 4 barrel manifold and carb from a guy that took it off his 66 383 Satellite (he put on dual quads).Also bought his rear leaf springs.
Carb story first.Put it on ,car started right up.Sounded good.Took it for a test drive. Flooded it in first, dropped the clutch and was off.Hit second gear,let up on gas ,engine was still screaming! Holy s— batman!Had wherewithal to quickly turn off ignition.Fortunately did not crash.Check carb, found out I put a heavier return spring on the secondaries. When I floored it it kept the carb wide open!
Stupid #2.Put on the new leaf springs.This was 1968 when having the rear end jacked up high was the way to go.The new springs had 2 more leaves then the original springs. Went to install driveshaft, found that shaft didn’t reach rear end.The center bolt of the new springs move the rear further rearward.
So to compensate, got a block of wood and some long carriage bolts and put it together. Test drive was about 50 feet.Bent the crap out of the bolts and snapped the wood.End using my original main leaf and added more from the Satellite springs.DUH!!


I changed the throw out bearing on a 1980 Mustang 4 banger back in the late 80’s, I had a spare trans from another stang that was nice and clean so I decided to install it instead of the original. I finished up and tried to start the car, when I spun it over the car tried to move even though it was in neutral with clutch in. Nothing I tried would work. Back under I went to remove the tranny. Needless to say it would not budge. I tried hooking a come along to the axle and pull the trans from the engine but no luck, it was welded to the clutch plate lol. I had to drill a bunch of holes in the bell housing and smash it apart with a hammer so I could get at the pressure plate bolts. I learned the hard way that some input shafts are a bit longer. I did all this in a dirt driveway. Gottta learn somehow


Owned a Fiat 600 in the early 70’s. I decided to replace the engine and bought a used one and replaced it myself. When I installed the “new” engine I forgot to install a spacer plate between the engine and transmission. After finishing the job I did a test drive and discovered that the clutch was slipping badly and realized my mistake. Had to completely remove the “new” engine and reinstall it correctly.


The dumbest mistake you can make is making an assumption without a full diagnosis. Here’s how I found
out: My first car was a 1959 MGA. On a 1st to 2nd shift I got nothing but a revving engine, no power to the wheels. Towed to a shop and diagnosed as clutch problem. Sure enough after pulling engine and gearbox(had to pull engine to get to clutch on MGA) they found the clutch plate disintegrated.
About a year later the same thing happened. This time, as a funds lacking college student I decided to do job myself. Borrowed a chain hoist and hung it from house porch,with car underneath in driveway, and with a friend’s help got the engine and tranny out in good time, BUT… when unbolted the tranny found the clutch in good shape! Only then did I reach through the shifter hole in the trans tunnel, grabbed the driveshaft and turned it easily with both rear wheels on the ground. Pulled the differential to find it a pile of broken spider gears and carrier. Installed the new clutch anyway (especially the quick wearing archaic non-rotating graphite throwout bearing, but that’s another story) reinstalled engine, and parked the car for a week until I could buy a junkyard diff. At least with a full floating rear end could put the wheels back on without the axles, and push the car around. That’s how I learned NOT TO MAKE ASSUMPTIONS!


Got impatient broke spark plug off, should of soaked down wth some penetrating oil


As a young guy, I got my MG MIdget out of Winter storage one year at my parents place and the ignition switch wasn’t working right. Off to the parts guy. It will take a week to get the part. I want to drive the car so I bought two toggle switches and a mounting plate, mounted the plate under the steering column, cut the old switch off the harness and wire one switch for ignition and the other for the starter. I get it all in, it works fine. I’m kneeling on the carport floor, leaning in, cleaning up the wire bits and tools off the floor mat and I inadvertently hit the starter toggle with the back of my hand. The starter spins and the car is in gear so the car takes off. I hang on for dear life and get dragged along the ground, wildly swiping at the switch to shut it off. I get to the switch after the car hits a movable plywood privacy barrier, knocks over the wood pile behind the barrier, crushes my Dad’s lawn mower and stalls. The first thing I do is jump up and check if anyone saw me. They didn’t. I then spent a few hours moving the wall back, restacking the wood pile and bending the mower handle back into shape. It worked out ok so I never mentioned it to my Dad. He never noticed the mower handle wasn’t quite stock any more. I learned my lesson, always work where nobody can see you make a mistake. :slight_smile:


I had just put a new mild cam and lifters in my 1965 Coronet w/ a 318 Poly. I was tuning the carb, working by myself, and stupidly using a remote start button. The car was cold and the carb on high idle. I hit the button and the car was apparently in reverse. It started immediately and took off backwards out of the garage at a high rate of speed, but the wheel was turned slightly to the left. The drivers door was open so I had to run from the front of the car, run around the door, and I jumped in and got it stopped. Unfortunately the wheel was turned to the left so it put the right front fender into the garage door frame, caught the tire, bent the lower ball joint, bounced off the tire, went back into the fender again, and I got it stopped 1 inch before it ripped the front bumper off the car. I pulled it back in the garage, shut it off, walked around and surveyed the damage, then immediately grabbed the remote start button and smashed it with a hammer. Then I sat down and started knocking out the 2 huge dents in the fender…the fender was perfect before that!!The bonehead move of bonehead moves!


Using a breaker bar to loosen a torsion bar while lying under an Xterra WITHOUT a floor jack. Snapped the torsion bar in half. Nearly gave me a heart attack when the wheel dropped down about 5 inches from me.


My Dad made sure what ever I learned, it was the hard way. He would give verbal instructions and leave. His 52 Chevy needed rear brakes. So to be safe, I placed a heavy duty wooden motor box under the axle on each side. After a long day of struggling with the brake job, it was time to go home. My Dad was puzzled as to why the Chevy had no go. He looked straight at me and asked me to run through what I did. It was then that I remembered my safety motor boxes. At 12 that was my first of many dumb mistakes


When I was a lil punk, working under my truck in the drive. It had just rained and the creek behind the house was out of its banks. Which had made this huge Wolf Spider seek higher ground. Right under the truck with me. Being a punk…did what a punk would do. I soaked him down good with WD-40. Then set him a fire ! I can’t imagine what it would feel like to be set on fire, but this guy heads straight for cover in my Dad’s shop. (not the tidiest) and found a gas covered rag. Now it too is on fire. Got everything out. How would you explain that to the insurance co. after the place burns down.


Amoral on the pedals…never gonna do that again.


@grapeape73 - Ooohhhh… Forgot about htat. I have done that one too. You are right. Never again.


I thought I was jacking up my Triumph TR3A on the frame BUT I had placed the jack under the radiator instead. Crushed it!


when I was a freshman in college, I had a '68 Thunderbird that burned a valve. Had to pull the intake and in the process, pulled the distributor without marking it. Didn’t catch my screw up until I went to put it back in. Spent a couple of extra hours checking position, which piston should be where, and then the moment of truth, cranked it up expecting the worst. Someone was looking out for me that day and things went well. Never forgot it, first thing I do now is mark it.


Mating the freshly rebuilt 401 engine to the 400 turbo transmission in my sons project Jeep and forgetting to install the bell housing plate between the transmission and engine. Even took pictures of the finished install and then looking at the pictures saw the plate leaning against the wall of the garage. Duh. Engine back out.


I hate to say it, but in the early '80s I was working for a friend in his automotive garage on a 1979 Buick Riviera replacing the rings and forgot to refill the front wheel drive differential (front wheel drive was new to me). The customer picked up the car and got about 15 miles away when the car came to a screeching halt. The differential had fried. I had to pay for a used differential and do the labor for free! I never forgot to fill a differential again after that!


I rebuilt a big block Chevy 427 and I forgot to snap the nylon coupler to the oil pump . I dropped the drive in and thought I didn’t hear it click in but I got distracted and didn’t pull it and check. The motor ran great for a few hundred miles until one very cold morning. 5 degrees I believe it was. I fired it up and had about 90 psi of oil pressure. I drove it nice and easy for a few minutes , then got on it. Soon the valves were tapping! Looked down and saw zero pressure and valves clacking away. The shaft broke both ears off the oil pump and the cam shaft wiped out 4 lobes. Very expensive mistake!


Overheating 65 Mustang. It would overheat on highway, but not at idle.
I installed a fan shroud, checked the circulation in the radiator, installed an aluminum radiator in place of the original. All to no avail. I didn’t replace the water pump since it was recently replaced by the dealer I bought it from.
One night, while standing in front of the car and puzzling over the idling engine, something caught my attention. I felt a breeze on my legs. It was then that I realized that I had spent hundreds of dollars before I felt that breeze caused by the FAN BEING INSTALLED BACKWARDS by the dealer when they replaced the water pump just before I purchased it.
Turned the fan around and all was well!


At age 19, I just tuned up my car for the 1st time ever to do such. I was proud! Just thought I’d make sure everything was snug tight. I then grabbed the ignition coil while the car was running! YOUCH!! :rage:. Never did that again.