c/diesel-mechanics

Old school vs. computer diagnostics on a 2008 Freightliner

I used to swear by my manual timing light and listening to the engine knock to set injection timing. After I picked up a used Autel scanner at a swap meet in Tulsa last spring, I quit doing it the old way. The computer caught a 2 degree offset I never would have heard, and that saved me from pulling the head on a customer's truck. Has anyone else switched over and found the digital tools are actually better for older stuff too?

Had a Cummins ISX eat a turbo on I-35 near Austin last Tuesday

I was hauling a load of lumber through Austin when the turbo let go at mile marker 238, sounded like a damn jet engine then nothing but black smoke. Cost me $3,400 to have it towed to a shop that found the oil feed line was clogged from sludge, which I should've caught on my last PM. Has anyone else had issues with these ISX turbos failing early if you skip the 50k mile oil analysis?

Had a shop owner scream at me for using a torque wrench on lug nuts

Hit a pothole outside Nashville that cracked my oil pan - now I always check my skid plate bolts

Was rolling through construction on I-40 near the 219 exit around 2am, didn't see that monster pothole till it was too late. Cracked the pan on my '18 T680, lost about 3 quarts before I caught it. Took me 4 hours on the shoulder to patch it up with some JB Weld and get to a shop. Ever since then I spend an extra 5 minutes every oil change making sure all those skid plate bolts are torqued right. Any of you guys run into a pothole that did some real damage?

Threw $80 at a cheap injector puller kit and instantly regretted it

I needed to pull some stuck injectors on a 6.0 Powerstroke last week and grabbed a budget puller kit off Amazon for 80 bucks. First one I used, the slide hammer threads stripped out on the second hit. Ended up having to torch and chisel the damn thing off. Now I'm out the money plus a whole afternoon. Anyone got a brand of puller that actually holds up to real use?

Old timer told me to run my engine hard to break it in, I thought he was crazy

Last year I bought a 2023 Cummins and this guy Bob at the shop in Omaha said to hold it at 2500 RPM for the first 500 miles. I figured he was messing with me, but I did it anyway. Truck has 40k miles now and runs like a top, no oil burn or anything. Anyone else get weird break-in advice that actually worked?

The week everything that could break... did break

Man, last Tuesday was something else. I had a 2004 F-250 roll in with a dead fuel pump, and I figured that'd be the big job of the day... swapped it out in about 3 hours, no sweat. Then the owner asks me to check a weird sound, and I pop the hood to find the serpentine belt shredded and wrapped around the fan clutch. Got that sorted, and just as I'm buttoning it up, the air compressor on my shop's lift gives out. Stuck with the truck half in the air for 45 minutes while I jerry-rigged a floor jack. By Friday, I'd also fixed a leaky injector on a Dodge and a bad turbo actuator on a Volvo semi. It was like the universe decided to test every diesel mechanic in a 20-mile radius of my garage. Has anyone else had a week where it felt like all the broken trucks in the county lined up at your door?

Unpopular opinion: Old timers who say to never use ether on a diesel are full of it

My grandpa Jake swore I'd blow a hole through a piston if I ever used starting fluid on a 7.3 IDI. He said if it don't start without it, somethings wrong with the glow plugs or batteries. But last winter my buddies F-250 sat for 6 months in the snow, batteries were fine but it would NOT catch. I cracked the glow plug relay and gave her a quick shot of ether, fired right up and has run fine for 3 months now. Has anyone else saved a cold IDI with ether against old school advice or am I just lucky?

Heads up on injector cups on 6.7 Powerstrokes

Had one crack on me last Wednesday during a routine injector swap on a 2015 F-450, dumped all the coolant out before I caught it. Has anyone else seen these fail without any warning signs beforehand?

Rant: That perfect 3 day stretch in Cincinnati last fall still bugs me

Everyone says a diesel shop needs chaos to stay sharp, but last October I had a Tuesday through Thursday where every single job went smooth - no comeback, no busted tool, a fleet truck overhaul finished a day early - and I swear it made the next two weeks feel twice as rough. Has anyone else had a run of good luck that actually messed with your workflow?

Had a 6.7 Powerstroke truck that changed my mind on oil change intervals

For years I ran 15,000 miles between oil changes on my Ford 6.7, thought the synthetic could handle it. Then I sent a sample to Blackstone Labs after 11,000 miles and they came back with high fuel dilution, told me to cut it to 7,500. I did that for two changes and sent another sample last month, numbers were night and day. The viscosity stayed right where it should be and wear metals dropped by almost 40 percent. That lab report was the proof I needed, now I'm a firm believer in the 7,500 mile mark for these trucks. Anyone else had Blackstone call them out on their maintenance habits?

Switched from impact wrenches to breaker bars on stubborn suspension bolts

I used to just grab my Milwaukee 1/2 impact and go to town on rusted control arm bolts, but after snapping two of them last year on a Ram 2500 I started using a 24 inch breaker bar with PB Blaster first. Now I let the penetrating oil sit for 15 minutes and crack them manually before the impact even touches it. Has anyone else had better luck breaking loose rusted frame bolts this way?

Why does nobody talk about fuel return line issues on 7.3 Powerstrokes?

I was hauling hay near Abilene last month when my '97 F-250 started dying under load. Spent two days chasing injectors before some old-timer at a truck stop pointed me to the return line crossover. Replaced the fitting for $12 and it ran like new. Has anyone else dealt with a simple fuel line problem that looked like a major failure?

Heard a kid say "just plug a scan tool in" and it got me thinking

I was grabbing parts at the local shop and overheard a younger tech say that. He was talking about how a scan tool will tell you everything, which is true to some point. But I remember spending hours tracing wires on an old 12-valve Cummins with just a test light and a multimeter. We learned the system by heart, not by reading codes. Has anyone else noticed newer guys skipping the basics because the computer does it?

That mechanic in Tulsa told me to skip the coolant flush on my 6.7

Guy at a shop in Tulsa said just drain and fill it every 30k instead of a full flush. Been doing it for 2 years now and my temps stay rock solid. Anyone else run into this debate about flushes on high-mileage engines?

Warning: using a cheap torque wrench on head bolts cost me a rebuild job last fall in Spokane

Was torquing down the heads on a Cummins ISX and the wrench clicked way too early, found out later it was 30 ft-lbs off at the high end. Anybody else had a harbor freight special fail at a critical moment?

I finally switched from conventional oil to synthetic in my old 7.3 and wish I did it sooner

Ran Rotella 15w40 in my 2000 F250 for the first 180k miles because that's what everyone told me to do. Last oil change I put in full synthetic 5w40 on a whim. Cold starts this winter in Maine went from 5 seconds of chugging to firing up instantly. Anyone else make the switch late and see a big difference?

The zip tie trick that saved me 3 hours on a stuck DEF injector

Had a 2015 Freightliner Cascadia in my shop last Tuesday with a clogged DEF injector that wouldn't budge. I tried heat, penetrating oil, even a breaker bar for 45 minutes with no luck. On a wild guess, I wrapped a heavy zip tie around the injector body and pulled it tight, then gave it a sharp tap with a hammer. The vibration broke the rust seal and it came right out with a wrench. Has anyone else used zip ties for anything weird on a diesel job?

Took me 3 rebuilds to realize I was overtorquing head bolts like a dummy

I kept having head gasket failures on a 5.9 Cummins I was working on. After the third time pulling the head, I finally sat down and looked at my torque wrench calibration. Turns out I was using a 3/8 drive torque wrench that was way off for the final angle torque step. The shop I work at in Denver has a calibration guy come through every 6 months, but I never bothered to check my personal wrench. I borrowed a calibrated one from a coworker and suddenly everything felt different. The bolts actually moved smooth instead of that jerky feeling I thought was normal. Has anyone else had a torque wrench give them false confidence for months before they realized it?

That time a farmer showed me a diesel fix I still use today

I was out near Lubbock last fall working on a irrigation pump and an old farmer walked over while I was scratching my head over a fuel issue. He just pointed at a little bleeder screw I had overlooked and said "sometimes the smallest thing is the biggest problem." After I got it running he showed me how he cleans his injector nozzles with a brass brush and diesel fuel instead of replacing them. Has anyone else picked up a trick from someone who wasn't even a mechanic?

Upside down injector trick is overrated

I keep seeing guys on here swear by the upside down injector trick for priming a new common rail system but I tried it last week on a 6.7 Cummins in my shop near Tulsa and it didnt help at all. Ended up with air in the rail for 2 hours before I got it sorted. What actually worked was cracking the high pressure lines at the injectors and cranking it for 20 seconds at a time until fuel dribbled out. Took 3 rounds of that and she fired right up. The upside down thing just made a mess and wasted my time. Has anyone else had better luck with just cracking lines instead of that trick?

Just realized my injector cups were the real problem

Had a 6.0 Powerstroke that kept missing under load for months. Chased injectors, harnesses, FICM voltage - the whole deal. Finally pulled the cups after 3 tries and saw micro cracks around the O-ring seats. Put new cups in and it ran like new the same day. Anyone else skip inspecting cups and regret it later?

That old timer at the parts counter got me thinking about glow plug maintenance

I was in at the local Cummins dealer in Lubbock last Tuesday picking up a set of injectors for a 5.9. This grizzled old guy next to me starts chatting while we wait, says he's been turning wrenches since the 70s. He goes off about how he replaces glow plugs every 50k miles on his own truck, even if they test fine. I always figured if the multimeter says they're good, leave em be. But he told me about getting stranded in a blizzard in 1985 because a glow plug failed internally after just passing a test. He said the electrical resistance lying to you is the number one hidden failure. Made me wonder how many trucks I've sent out with borderline glow plugs that could pop any time you need them most. Any of y'all run into glow plugs testing good but still causing hard starts?

Stopped at that old diesel shop outside Flagstaff last week

I was heading back from a job in Phoenix and my check engine light came on just past the Arizona line. Pulled into a place called High Desert Diesel, looked like it had been there since the 70s. The guy who came out, must have been 70 years old, walked over with a screwdriver and a stethoscope. He put that stethoscope on the injector lines and listened for maybe 30 seconds. Said I had a sticky injector on cylinder 4, popped the line, tapped it with a wrench, and the idle smoothed right out. Charged me 20 bucks and told me to run some cleaner through it when I got home. Made me wonder how much time I waste chasing codes with a scanner when the old guys just listen and know. Has anyone else run into a mechanic like that who still works without a computer?

Shoutout to the guy at the truck stop in Wyoming who showed me a trick for frozen fuel lines

I was stuck outside Laramie last January with a 2012 Freightliner that just would not start. Temperature was hovering around negative 15. A older mechanic who was passing through took one look and told me to pour a little bit of isopropyl alcohol into the fuel filter housing. It broke up the ice crystals in about 10 minutes and the engine fired right up. Has anyone else ever tried this instead of using those expensive fuel additives?