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


Mine is embarrassingly recent… Bought a ‘48 Ford Convertible back in October. Had it shipped from upstate NY to MD with no problems. The driver of the shipping company unloaded the car and parked it in our driveway, again no problems, and hands me the keys. He goes on his way and I go to start the car… I put the key in, turn it all the way to the right, and nothing happens… I try it a couple of times and nothing… I start to get upset and start trying to figure out why all of the sudden the car will not start… Then the embarrassing light bulb goes on over my head and I remember that back in 1948 cars had starter buttons! Duh… Problem solved!


Needed to replace a severely rusted oil pan on my '04 Ram 2500 pickup with 5.7L Hemi.
I read the service manual. They always say to start by disconnecting the battery. Why do that when you are not servicing anything electric?
I’m laying on my back under the truck, the old pan is off. I’m looking at the bottom of the crank, with my hands in close proximity. All of a sudden I hear the electric fuel pump start up, and the engine starts to crank with me under it!.
It turns out I had the keys in my pocket with an after-market remote starter fob. When I was rolling around under the truck, I had inadvertently pressed the remote start button!
Fortunately I had the presence of mind to understand what had happened and was able to abort the start.
After thinking about it some more, I wondered why the truck would start with the hood open. It had a safety switch that was supposed to prevent starting if the hood was open. A quick check showed that safety switch was broken (open) which allowed the engine to start.
I replaced the safety switch, and I also now make certain to remove the battery cable, especially on this vehicle before I work on it. I don’t like sudden surprises.


Last January, had a slow leak on the left rear tire of my 63-1/2 Galaxie. I got the floor jack out and placed an 8" x 8" by 1-3/4" thick piece of plywood on top of the jack seat or pod which is about 3 inches in diameter. Jacked the car up under the frame, took the wheel off and check the tire for a screw or nail, checked the valve stem and valve in the stem, it wasn’t done up tight, hence the slow leak. I tightened it up and proceeded to put the wheel back on, I got it almost on through the stud holes and the 8 x 8 block split, the car dropped down but not in the blink of an eye, it just slowly broke the plywood and a chunk of the wood wedged against the gas tank and the jack… Lucky no leaks in the tank, but I had to buy a new gas tank which cost me all of $800. Should have taken a little more caution. Just lucky myself and hands were clear when the car dropped.


Opening the tool box and starting the job.


Put front and rear pads in my sons first car Crown Vic ex squad car , told him to pump the pedal and back it out to the shop door. Of course he thought the I meant the gas pedal before he started it up.
Hit reverse and well you can guess the rest.
By the time he stopped , he had it turned off, ebrake on and in park, just as he went through the open shop door and backed into my pickup. With eyes like saucers he is freaking out about the bumper until I mentioned that I had a brand new one in the shop for it and the door had been open. An hour later and one new bumper somebody learned a very good lesson.


Allowed the oil pump hex drive shaft to fall out of the distributor while attempting to re-engage the teeth on the cam. First start-up of a 58 Ford 300hp, 352ci FE Interceptor engine we just rebuilt and needed to move the distributor a couple teeth for timing. Hex slipped out of the oil pump and made its way to the bottom of the oil pan with a resounding “thunk.” After a day of “fishing,” pulled the engine and the pan to retrieve it. Peened a dimple on the oil pump end of the shaft this time to keep it in the oil pump when pulling the distributor. Lessons learned!


I pride myself on being a backyard mechanic. We have all replaced the wrong part to no avail at one point or another. Well i have a early 2004 BMW all wheel drive wagon. Front drivetrain making the typical front wheel drive sound of time to replace the axle. Waited to long the vehicles trans axle cuts out. Need a tow home. No big deal.Hey NAPA on speed dial. Time constraints renders to rent a car for a week. Fight with the old axle but eventually it comes out in two pieces. Install new one drive around the block, life is good. We all know that feeling of being a back yard mechanic master. You know the master of my domain. Anyway the rental car gets returned and I am off. Well for about four or five miles, and she loses the drive again. Repeat tow truck and rental car. All appears to be trans axle issue. Confirmed by other backyard mechanics as well. So I purchase another Bmw Wagon. Park the three series. And away I go for about 60,000 miles or so till I have problems involving taking the head off. So i return to the original project be having it sent out to the shop. Ready in a few days at a reasonable cost and I ask what was the problem. He says the front axle. Apparently I replaced the wrong one. Go figure.


Too many to list.Would take a week to list them all. LOL


The weirdest experience I ever had was with one of the many Volvos I have had in my life. It was a 122 wagon that I bought as a winter beater. It ran great but on a run back into town there was a low thump and all of a sudden was not running on all cylinders. And under closer examination had developed an oil leak from the rear of the motor. Now these B18 motors were basically indestructible, but after checking everything I figured it must have been a blown head gasket, even though head gaskets NEVER go on these Volvo motors. So I pulled the cylinder head and replaced the head gasket and began to button everything back up. Easy-peasey! After torquing the head down and re-installing the rocker arm, I set to adjusting the valves. Everything was going well until I noticed cylinder four had no movement on the valve gear! Whaaa? I ended up pulling the motor at which time I found the source of the oil leak. The core plug at the rear of the camshaft was out of place! So I pulled the head again, then pulled the camshaft out. It turns out the cam had broken just behind the distributor drive gear, leaving the last two lobes idle. When the cam broke the loose piece jumped backwards and dislodged the core plug. The amazing part is the engine had kept running! I replaced the cam, and installed another head gasket, and got the car back up and running. I have never seen another incident like this ever, and I still have the broken camshaft in my tool box to remind me of the weird things that can happen with an automotive engine!


I was 17 or 18 years old
Chev 350 had a normal ticking noise but a friend who didnt know anything said sounds like you have a bent pushrod. So i proceeded to take the intake off WITHOUT DRAINING ANY COOLANT

rod was fine put it all back togeather but the engine died not long after all the coolant got circulated.

Beat that dumb job


Was working on exhaust leak on my 68 gto had to drop starter and reinstalled it with battery cable angled wrong and it shorted as soon as i accelerated. It was dark outside and everything went dark on the car, smoke poured out from under hood. I opened the hood to find a bright orange glowing hot cable from battery to the starter. I was able to break it loose with the tire iron, clean things up and push the car to get it started and drive home. I keep a pair of cutters in the glovebox now just in case.


In 1979 I was installing a new water pump on a '71 MGB. When I finished the job, cranked up the engine and heard a heart-stopping crash. I had left a wrench sitting on the radiator, which fell into the fan, which then propelled the wrench through the radiator. Back to the junkyard for another fan and radiator. Won’t make that mistake again anytime soon.


I ran my front brakes down to the rivets on my 68 GTO and kicked myself for that. I was able to separate the old drums from the hubs somehow even though they were swaged together at the wheel studs.I bought 2 new drums and cracked one of them trying to force it over the wheel studs that had been swaged to hold the old drum and hub together. Back then it was my daily driver and I was in a hurry to get it back together. It was a little embarrassing ordering a third drum at the parts counter.


Working as a mechanic over 40 years ago, I left a 1/2" socket in the intake valley of a 73 Impala 350cu. in. V-8.
Heard it rattling around a little bit, but since it was too long and wide to get caught or do any damage, I left it in there. Owner drove the car for two more years, never complained about any noises. Also, I changed the tires on a mint 1966 Mustang, owned by a Sargent with the local police. While yapping and not paying attention, I never tightened down the rear lug nuts, just slapped the wheel covers on. Things got wobbly while backing out of the bay, thank God nothing happened, stopped the car, jacked it up, and tightened things up. The guy was really pissed off.


Change a rear axle bearing on 60s GM and forgot to put the axle retaining bracket on before the bearing. Had to destroy the new bearing to remove it and then install another new one. Luckily they were only about $15 at the time.


Back in 1979 I had a buddy in high school that was working on his firebird. He had removed the left rear wheel to for something and when he went looking for the wheel to reinstall he couldn’t find it. It had rolled out of the garage down the driveway and turned left. He found it about a block away in the woods.


There’s so many it’s hard to pick the DUMBEST, but this is one of the most entertaining. I bought a “well used” '69 GTO. The carb was garbage, several of the pushrods were bent, some badly (!), and three of the hydraulic lifters had broken retaining clips and had spewed their innards. Got it all back together around 2 AM (with a '66 tri-power that I had on hand) and I decided to do the test drive thing. Started right up and purred like a kitten. Well, like a tiger cub, I guess. I put it in reverse and backed down the driveway into the road, but when I shifted into drive it just sat there. Fuming, I got out, threw up the hood, and, sure enough, the trans dipstick came out dry as a bone. I walked back up to the shop and got a couple of quarts of ATF & a funnel, put them in, and it’s still dry. I hiked back up to the garage and grab another couple of quarts and when I turn around, there’s the GTO slowly driving away. I’d left it running and hadn’t thought to put it back in park. It had enough of a head start that I had to chase it nearly a block before I could dive through the driver’s window and slam the shifter into park. Thank Heavens for straight roads, and I’m glad that it happened when I was a kid, because if I tried to pull it off today I’d give myself a heart attack!


Yeah my 68 GTO was pretty well used. Called a “mechanics special” in the autotrader. Had to tow it home. I was working on the carburetor one of many days and buttoned it all back up, started the engine and adjusted everything. It was purring, so I took it for a test drive and noticed a strong gas smell when I got back. I had forgotten to tighten the clamp on the fuel hose and the engine was completely bathed in gas. Oops.


@craigpartridge - Damage stinks, but the fact he had the presence of mind to shut it off, get it into park, and hit the parking brake says he had some decent wit about him!


I did a transmission swap on my '86 Omni GLH Turbo and forgot to install the throwout bearing. That was in the days when I was still learning about cars, so a lot of mistakes were made back then.