What is the worst mistake you made doing your own wrenching?

a long time ago my neighbor was working on a chevy vega.
he had his socket set and some tools balancing on/near the radiator
when he said he was going to try to start the engine and wanted
me to watch for something. well the socket set fell into the fan
and that was the first and only time i got hit by a 9mm.

 

As a teenager l did a NASCAR style quick brake change, ran in the house took a shower, ran back out and jumped in the car, dumped the clutch to back down a super steep driveway, pedal went straight to the floor so I dove for the handbrake and thankfully slid to a stop. Have never been in a hurry to do anything on my vehicle since then, double check things and take my time.

 

Wasn't catastrophic... but when I was 17 I drained my transmission thinking it was the oil drain bolt on my explorer... Was a sealed tranny and had to tow to dealer for refill service to be done. I double check every single time now... and think of my teenage mistake with each oil change since.

 

I went on TW and got advice from internet engineers. It ended badly. You should hear the mistakes from the same people who think they are qualified to tell others how to do stuff.

 

Considering I have a new front bumper on order that will require cutting the front of my new truck this thread is making me very nervous lol. Hope I’m not contributing to it shortly.

 

Changed the oil on my teams KTM500EXC in the middle of a Mexican 1000 race in Baja. Put the oil drain plug back in and took another drag on the tequila bottle. Grabbed the ratchet, extension and socket and gave what I thought was the drain bolt a grunt. Later that day we got a call on the radio that the bike was broken down and all the oil had drained out. Got to the place where the bike and rider were waiting. Yep, oil drain plug was missing and there was a big puddle of oil. Luckily, the oil drained out at a check point and was noticed by someone. We hauled the bike to the next town, pulled the valve cover, inspected everything, found and installed another drain plug, topped off the oil and got the bike back in the race the next morning. Turns out I tightened the wrong bolt. Lesson learned-wait until rest stops to drink tequila and safety wire drain plugs.

 

I cracked a water pump bolt in my 280Z back in ‘the day’. We ended up taking the whole front end off and buying a nice tap set to get that thing out. Took the weekend, but other than time and knuckle skin, I wasn’t out anything additional.

Oh, and the biggest boneheaded move? I was detailing the engine bay in my first car... ‘72 El Camino. Decided that all the spark plug wires needed to be rerouted so they were more ‘organized’. That didn’t go well. At least my stepfather got a good laugh out of it. Pretty easy fix once we found the firing order.

 

ECGS Bushing, couldn't get the diff seal to seal, tapped it in, used the 2" pvc coupling, checked cv joint with caliper, had it all apart 5 times,............... helps if you don't put it in backwards!

 

Those seals are a real bitch. I’ve had to replace my passenger one 3-4 times because apparently I suck at installing them.

 

In high school, we were getting ready to go on a road trip for thanksgiving (700 miles each way) and the weather looked bad. I thought I’d help out and swap from summer wheels and tires to the snows.
About 250 miles into the drive on I-90, Mom is driving and we start hearing a noise, then a vibration. Weird. Driver side rear drops and the car heads for the median in a shower of sparks. Mom did a great job maintaining control and was able to stop on the shoulder. The rotor left a groove hundreds of feet long and 1/2” deep. Dad and I had to rent a car to go find the wheel and tire the next day which had crossed the median, the opposite lane, hopped a fence and landed on the cover of someone’s above-ground pool. When we got back to the shop dad taught me how to use a torque wrench. Luckily there were no vehicles near us when the wheel came off.

 

The biggest mistake I’ve made wrenching is to let things snowball. A check of a VW VR6 engine timing chains turned into a full blown rebuild. The chain tensioners needed to be replaced, but to do that you have to drop the transmission. If I’m doing that I might as well replace the clutch and add a lightweight flywheel. It’s not much more work at that point to swap in a limits slip differential. And swap the cams out. Or to replace the head gasket. And if the heads off I might as well rebuild it with new valves, stem seals, springs, lifters, etc. And while the head is off it’s easy to check the condition of the cylinder walls and piston skirts, and they don’t look perfect so it’s easy enough to do new pistons and bottom end bearings. That’s an easy way to turn a fairly simple weekend $200 job into a month long many thousand dollar job.

 

I can see that. The oil screen and drain plug are pretty much right next to each other.

 

Too much red threadlocker !! You don’t even know how much u stuffed up for such a long time

 

Have one from my stepdad. Back in his hotrod days they were building a ratrod from spare parts they scrounged from, lets just say 'places'. Since all the parts were coming from various donors, nothing mated up well. Particularly they were struggling with the rear diff. One of them has the bright idea to flip it over and it'll make things soooo much easier. 4 reverse gears and 1 forward gear later, they're figuring out that wasn't such a bright idea.

 

Had a 98 Wrangler 5 speed I put a new clutch in(first time clutch replacement) put everything back together and clutch wouldn’t pull in. Pulled it again and reinstalled.. same problem, pulled again and opened it up. Cleaned and reassembled (should have clarified, I disassembled the whole transmission..literally had a pile of gears on my bench)reinstalled and still the damn thing didn’t work. Light bulb goes off...I gotta bleed the slave cylinder and line. Worked great after that.

 

Was it worth it? That’s what matters.

 

Changed the water pump on my 07 yaris. When putting the alternator and belt back on, I was prying on the alternator to tension the belt against what I thought was the block, but apparently it was a oil valve timing sensor and I broke it. Luckily it was only about a $2-300 fix.

 

so about half the cost of the car?