c/diesel-mechanics

Swapped to synthetic oil in my 2007 6.0 and lost fuel economy

Last month in Boise I finally switched from conventional to full synthetic on my work truck, and my average dropped from 14.2 to 13.1 mpg over 800 miles. Everyone online swears synthetic is a no-brainer, but has anyone else seen worse numbers after the change or is my injector stiction just messing with me?

Found a $8 harbor freight pry bar that beats my $60 one for injector cups

Stripping injector cups on a 6.0 in Columbus last week and my Snap-on kept slipping. Grabbed a cheap HF flat bar from the truck, ground the tip down to a chisel edge, and it popped all 8 cups without any fuss. Used it with a slide hammer adapter I rigged from an old u-joint. Anyone else modding cheap tools for specific jobs instead of dropping cash on the fancy stuff?

Roadside repair in Flagstaff turned into a full audience event

Stopped at a Love's off I-40 in Flagstaff last Tuesday to fix a blown air line on a Peterbilt. The fitting on the brake chamber had stripped, so I ended up replacing it with a 3/8 compression fitting from my truck kit. Next thing I know, three drivers walked over and one guy in an International was holding my flashlight, another handed me his crescent wrench. Has anyone else had a simple roadside fix turn into a group project with about 15 minutes of helpful advice?

Injector stuck open, cooked a piston on I-80

Freightliner started missing hard near Joliet, smoke rolling out the stack. Pulled the head and found injector 5 stuck open, piston crown melted on one side. Anyone run into this with a specific common-rail pump causing repeated injector failures? I'm looking at replacing the whole fuel rail next.

Chased a phantom misfire for 6 hours, turned out to be a bad ground strap

Hauled a 2019 Freightliner into the shop last Tuesday. Driver said it was missing hard under load, throwing no codes. I replaced the fuel filters, checked injector return rates, went through the whole intake path. Six hours in, I finally noticed the ground strap from the block to the frame was cracked right where it bolts up. Cleaned it, tightened it, fired it up and it ran perfect. That little strap stole half my day. How many of you have burned hours on electrical gremlins that turned out to be simple grounds?

Oil sample said copper, I ignored it for 2 more oil changes

Ran a Cat C15 in my dump truck, 420k miles. The lab report came back with high copper and I figured it was just normal wear. Truck ran fine, no noise, no smoke. Then last month the main bearing went at mile 78 on a loaded run near Fresno. Tore it down and the crank was scored bad. That copper was the bearing material telling me something. Cost me $6,800 for a used crank and bearings plus 3 days of downtime. Has anyone else had a lab result they shrugged off and paid for it later?

Swapped my old injector puller for a slide hammer set on a job in Tulsa

I always used the old screw-type injector puller on 7.3 Powerstrokes. Worked fine for years, no complaints. But last week I had a 2000 Ford with a stuck injector that would not budge. After 45 minutes of wiggling and cussing, I borrowed a buddy's slide hammer set from his truck. Popped that thing out in maybe 3 minutes tops. I was dead set against slide hammers cause I figured they'd damage the bore, but he showed me the right adapter and it came out clean. I ordered my own set that night. Has anyone else been converted to a different tool for a job you thought you had figured out?

Had to pick between a used $800 injector tester and a $1200 new one

I was looking at buying an injector tester for my shop last month. The used one was an old Bosch unit from a guy selling out of his garage in Des Moines. I went with the new one because the used had no warranty and looked beat. Turned out the new one works fine but honestly the savings would have been worth the risk.

Watched a guy at the PACCAR shop rebuild a 15-speed Eaton Fuller from memory

I was at the Kenworth dealer in Spokane last Thursday picking up a part for our fleet truck. One of their old school mechanics was putting together a 15 speed transmission without looking at any manual, just grabbing synchros and bearings by feel. He had every gear stack laid out on a clean mat in the exact order they came off. I stood there for 20 minutes just watching, and he didn't even glance up once. Has anyone else seen a rebuild done that fast without any reference material?

Had to pick between a used Snap-on scanner or a new Autel last month

I was staring down a $3000 budget for a diagnostic tool after my old one bricked on a job. The Snap-on was a 2017 model with no updates left for $2200, and the Autel was a brand new MX808 for $1800. I went with the Autel cause I figured updates matter more than a nameplate. Three weeks in, I had to use it on a 2024 Freightliner and read DPF regen data no problem. The only thing I miss is the Snap-on's build feel, but the Autel does everything I need. Anyone else choose new tech over used premium and regret it or not?

Stop using anti-seize on every bolt you touch, especially on a DPF equipped truck

Stripped a head bolt on a 6.0 Powerstroke in a parking lot outside Tulsa back in 2018

I was doing a buddy a favor fixing his work truck in a Walmart lot. The bolt just gave out at 130 ft-lbs and I had no tap and die set with me. Had to drive 45 minutes to the nearest NAPA and buy a thread chaser kit. That one mistake added 3 hours to what should have been a 2 hour job. Now I never leave home without a full tap and die set in my service truck. Anyone else learned the hard way to bring extra tools on a simple job?

Logged 200K miles on a single set of injectors and I'm still kicking myself

Heard a loud bang at a truck stop in Oklahoma that made me change my whole inspection routine

I was fueling up at a Pilot off I-40 last month when a tractor next to me let out this gunshot sound. Turned out the driver had a cracked flywheel housing he'd been ignoring for two weeks. The shop there said they see three of those a month from guys who skip the bottom end checks. Now I drop the inspection cover on every Class 8 that comes through my bay and look for hairline cracks with a flashlight. Has anyone else caught a major failure that way before it got expensive?

Tried ultrasonic cleaning on a set of injectors and one came out seized solid

Last month I had a set of Bosch injectors from a 6.7 Powerstroke that were all gummed up with carbon and old fuel deposits. Figured I'd throw them in my new ultrasonic cleaner with some heavy duty diesel cleaner for 30 minutes at 140 degrees. Five of them came out looking brand new and sprayed clean. But the sixth one had something weird happen. The ultrasonic vibrations must have loosened up some grit deep inside the nozzle and it wedged the needle valve shut. I couldn't even get it to budge with a brass punch. Now I'm wondering if I should have pulled the nozzles apart before cleaning them or if the cleaner was just too strong for that one injector. Has anyone else wrecked a part with an ultrasonic bath?

PSA: That time I caught a fuel line fire with a rag and a prayer

I was working on a 2015 Freightliner Cascadia outside Birmingham last Thursday. Had the engine running to check for a leak after replacing an injector cup. Fuel sprayed right onto the exhaust manifold and lit up before I could even cuss. Grabbed a shop rag and smothered it out fast, but melted half the wiring harness on that side. Took me 3 hours to splice in new wires and replace the burnt injector harness. Cost me about $150 in parts and a full afternoon. Anyone else had a fire scare that made you change how you test for leaks?

Shoutout to the old mechanic who told me to swap injectors before chasing air in the fuel system

Spent 3 hours bleeding lines on a 7.3 Powerstroke last Friday only to find out a stuck injector was dumping fuel back into the return rail instead of the cylinder, so has anyone else wasted a whole morning chasing a ghost like that?

Got chased by a bull at a farm call in rural Ohio last spring

I went out to fix a busted hydraulic line on a feed mixer at this dairy farm near Millersburg. The owner said the bull was locked up but he forgot to latch the gate. I was under the truck running a new hose when I heard hoofbeats and looked up to see a 2,000 pound Angus staring at me from 20 feet away. I dove back in the cab and sat there for 20 minutes until the farmer came out with a bucket of grain. Now I always check every single gate and pen before I crawl under anything. Has anyone else had a close call with livestock on a farm job?

Can we talk about passing 200 engine rebuilds without even noticing?

I was going through my old job logs last night trying to find a specific invoice from 2019 and I counted em all up. 217 full rebuilds over 12 years at the same shop. That number hit me weird because it doesn't feel like that many when you're just doing one at a time. Most of em were old Cummins N14s and Series 60s. The first one I did was a 1999 Freightliner with a wet cylinder liner issue and the old guy I was learning from had me measure everything three times. Now I can almost tell by feel when a liner is seated right. Has anyone else kept track of something like this over a long career and been surprised when you actually add it up?

Old timer's advice on fuel filters saved me $800 last winter

Back in 2019, a grizzled mechanic named Tom at the Union 76 near Bakersfield told me to always replace the water separator on a Cummins ISX before winter hits. I ignored him and ended up with a frozen line on I-5 in December, costing me a tow and two days of lost work. Has anyone else had a seasoned mechanic give advice that paid off big?

Hit 500 engine overhauls last Tuesday and it felt less like a milestone than I thought it would

Everyone acts like hitting a big number means something but honestly it was just another job same as the first one. Did anyone else get weirdly neutral when you passed a big count?

Why does nobody talk about how hard it is to find a good fuel injector guy these days?

Last month an old timer at a shop in Bakersfield spent 20 minutes showing me how to clean a set of injectors by hand instead of just swapping them, and he said 'you gotta learn the feel of it, not just the part number.' Has anyone else run into a mechanic who actually took the time to teach something like that instead of rushing through the job?

Old timer at the local diesel shop told me to quit using ATF in my fuel

I've been putting a little automatic transmission fluid in my diesel fuel for years, figured it helped with the injectors. An old mechanic named Dave over at Bob's Truck Repair told me it was just gumming things up on modern common rail systems. I ignored him for about 6 months until I had to pull my injectors on my 2012 Ford 6.7 and found them caked with varnish. Cost me $340 to have them cleaned and now I just use a proper additive. Anybody else get bad advice from an old timer that ended up costing you?

Unpopular opinion: torque wrenches need way more respect than they get

I was working on a Cummins ISX15 last Tuesday over at Johnson Fleet Service in Tulsa. Had a buddy who always just ugga-dugga'd his head bolts and laughed at me for taking time with my torque wrench. Three years ago he blew a head gasket on a rebuild and it cost him $4,500 and three weekends. Now he borrows my Snap-on every time. Has anyone else seen a guy learn this lesson the hard way with their own engine?

I used to think aftermarket injectors were junk until I put 200k on a set from Oregon Fuel Injection

For years I only ran OEM Bosch injectors on my Cummins builds, but a shop owner in Spokane talked me into trying a set of reman units on my personal truck. What convinced you to switch sides on something you thought was a bad idea?