c/diesel-mechanics

Rant: That 'it's fine' customer who handed me a death trap

Last spring a guy rolled into my garage in Missoula with a lifted Ford that had a driveshaft u-joint so loose I wiggled it with my pinky. He said 'just top off the oil and send it' and I had to flat out refuse to let him leave without a tow - you ever have someone argue with you about their own safety like that?

6 hours to find a 10-cent o-ring on a Cummins ISX in Nashville

I swear I almost pulled my hair out last Tuesday on a 2015 Peterbilt. It had this weird oil leak from the front cover that looked like a main seal job at first. I spent 4 hours chasing it down, pulling stuff apart, cleaning everything, running the engine, nothing. Then I noticed a tiny drip coming from a random bolt hole on the timing gear cover. Turns out there's a stupid little o-ring under a cap plug that nobody ever checks. Replaced it for like 10 cents and it fixed the whole thing. Made me feel like a complete idiot but also kinda proud I didn't tear the whole engine down. Has anyone else wasted a whole day on a simple gasket or seal that was hiding in plain sight?

Just realized how much fuel I waste idling in the lot every morning

I was sitting in my truck at the depot last week waiting for my dispatch sheet to come through and I got curious. Did some quick math off a fuel consumption chart I found online and figured out I idle about 20 minutes every day before even rolling out. At 0.8 gallons per hour that adds up to like $50 a month just burning diesel sitting still. Now I'm wondering how many of you actually shut down and restart versus letting it warm up for that long.

Took me 8 hours to diagnose a no-start that was just a bad ground

I had a 2012 Freightliner Cascadia that wouldn't crank, and I spent all damn day checking injectors, fuel pressure, and ECM power before I finally found the ground strap from the block to the frame was completely corroded. Has anyone else had a simple fix like that eat up a whole shift?

Just realized my old mentor had it right about fuel filter timing

Am I the only one who sees guys cranking torque specs way too high on injectors?

I was helping a buddy swap injectors on a 6.0 Powerstroke last weekend and he just grabbed his torque wrench and went straight to 30 ft-lbs without even checking the manual. I told him to stop because those hold-down bolts are only supposed to be like 18-20 ft-lbs on most of these big diesels. He argued with me saying "it needs to be tight to seal" but that's exactly how you crack the bore or strip the threads in the head. I've seen it happen twice now at a shop I used to work at in Denver where guys cranked them way over spec and ended up pulling the head off to fix a leak that wasn't even the injector's fault. The real trick is to clean the bore super good with a wire brush and some brake clean, then torque to the exact spec for that engine family. Has anyone else run into this where guys just go by feel instead of looking it up?

Swapped from synthetic to conventional oil on an old Cat 3406 and it stopped leaking

My mechanic buddy swore the synthetic was too thin for the high miles, so I tried conventional and after 2 weeks the drip under the pan went away - has anyone else seen that with older engines?

Stopped by a fleet garage in Salt Lake and saw them using an impact on oil drain plugs

I was dropping off a part at Johnson Fleet Services last Tuesday and watched two guys zip off drain plugs with a cordless impact. They did it to four trucks in a row without once touching a torque wrench. I told the lead mechanic that's a good way to strip threads or crack a pan and he just laughed and said they've been doing it for 5 years with no issues. Am I wrong for thinking this is a bad habit or is everybody doing this now?

Compared open element injectors vs pintle style on a 7.3 Powerstroke

Last month I swapped out my old pintle style injectors for open element ones on my 7.3. Thought it would be a simple upgrade. But the open elements made the engine run rough at idle and fuel economy dropped by 2 mpg. After three weeks of messing with tuning I put the pintles back in. Engine smoothed right out and my mileage went back to 18 mpg highway. Has anyone else had better luck with one type over the other?

TIL a simple brake bleed trick that saved me 3 hours of frustration

I was working on an old Freightliner last week, the rear brakes were spongy no matter how many times I bled them. I tried the standard two-person method, then a vacuum bleeder, still felt like mush. Finally a shop foreman walked over and told me to crack the bleeder screw at the master cylinder first before doing the wheels. I felt stupid but I tried it, and sure enough there was air trapped right at the top that was never getting pushed out. After that, the pedal was rock solid in like 20 minutes. Has anyone else dealt with air pockets hiding in weird spots on these older trucks?

That engine fire on I-95 taught me a hard lesson about zip ties

I was rolling southbound near Richmond last Thursday when I saw smoke pouring from under the hood of a 2015 Freightliner. Pulled over and popped the hood. A fuel line had rubbed through where I had zip tied it too tight against a bracket. The vibration wore a hole in it over maybe 6 months. Dumped a bottle of water on the small fire and called it lucky. Now I use those rubber-lined clamps for anything near moving parts. Anyone else had a fix come back to bite them like that?

PSA: Stop using brake cleaner on wheel bearings before packing them

I saw two different guys at the shop this week spray brake cleaner all over fresh wheel bearings before packing them with grease. That stuff strips every bit of lubricant off the metal and leaves them dry. Did it on a Peterbilt last month and the bearings were squealing after 200 miles. Why would you wash off the factory coating and then think grease alone is enough?

Just realized I wasted $400 on a fancy injector tester

Bought one of those digital injector testers last year thinking it would save me time. Turns out the old manual pop tester I had did the same job just fine. Anyone else buy a tool they barely use?

20 years in and I just learned I was torquing head bolts wrong

Been doing diesel work since 2004. Always did the torque sequence in a circle, never paid attention to the pattern. Last month a Cummins ISX guy came through my shop, watched me for 2 minutes, and just shook his head. He showed me the factory manual pattern starts from the center and works outward. 18 bolts, specific order, dead serious. Makes total sense now but man, all those years.

Pro tip: swapping to Teflon tape on my injector line threads cut my leak repairs by about 80% in just two weeks

I started using it after a guy at the Cummins shop mentioned it during a coffee break and it stopped those annoying seepage issues on my 5.9L, has anyone else tried this on high pressure lines?

Shoutout to the old guy at the Fleet Pride parts counter who told me to stop using starting fluid on my 7.3 Powerstroke

Back in 2018 I was fighting a no-start on my F-350 in Davenport, Iowa. I was ready to spray ether all over it like I always did. He grabbed my arm and said 'son, you're gonna break glow plugs or worse, burn the truck down.' He showed me how to check the glow plug relay with a test light instead. Did that, found a bad relay, swapped it for $35, fired right up. Saved me a tow and possible fire. Anyone else get handed a golden tip from an old parts counter guy?

Question about the $1200 Jasper reman I dropped in a 6.0 last fall

Did that Jasper rebuild save my shop hours or just burn my customer with a ticking time bomb because that thing already has a weird knock at 15k miles and I'm starting to wonder if those cheap in-frame kits from the parts house would have been smarter.

Question about an old master tech's advice on injector timing

Had a 30-year veteran at the shop in Tulsa tell me last week to stop chasing factory specs and listen for the knock instead, and now I'm wondering if I've been overthinking 90% of my rebuilds since I started.

30 minutes turned into 4 hours on a simple injector swap

I had a 7.3 Powerstroke in my shop last Tuesday that just needed one injector. Simple job right? Well the glow plug tip broke off in the prechamber when I pulled it. Had to pull the head off to get it out. Customer was standing there watching the whole time too. That extra labor cost him almost $600 more than the original quote. Has anyone else had a straightforward job just totally fall apart like that?

Spent $600 on a fancy injector puller kit and it was junk

Bought a Master Injector Puller set from a tool truck last spring. First time I used it on a 6.7 Powerstroke, the adapter threads stripped out. Cost me another $200 to have a machine shop fix the head. Went back to my old two-jaw puller and never had an issue since. Anyone else get burned by overpriced specialty tools that don't hold up?

I used to rebuild injectors in a clean room now I do them in my truck bed

For 8 years I worked at a shop in Tulsa where we had a sealed off room just for injector work. HEPA filter, static mats, the whole deal. Took it for granted. Got laid off last March and started doing mobile work. First time I had to rebuild a set of HEUI injectors in a dusty parking lot I panicked. But honestly? Wipe everything down with brake clean, work fast, bag the parts as you go. Done maybe 30 sets this way now and zero come backs. Has anyone else had to downgrade their workspace setup and found it works fine anyway?

Heard a guy at the parts counter say never use impact guns on injectors... now I get it

Surprised how a 100-hour injector service changed idle quality

Has anyone else seen a set of injectors that looked fine but turned out to be the whole problem?

I think everyone's wrong about oil change intervals on newer trucks

At a shop in Phoenix last spring I had a 2020 Ram 2500 come in with 45k miles running great. Owner had been going by the computer every 15k miles like the manual says. Everyone at my shop was freaking out saying that's way too long between changes. But I pulled the filter and sent the oil to Blackstone Labs and it came back fine. Now I'm starting to think these 15k intervals are actually fine with the right synthetic oil. Has anyone else actually tested their oil instead of just guessing?

The time I tried chasing a fuel pressure issue on an older Cummins ISX and swapped three sensors before finding a $12 crimp fitting that was loose under the cab.

Spent last Saturday in the shop tearing my hair out over a 2015 ProStar that kept dying on hills, only to realize a bad ground connection at the frame rail was the real culprit, and now I'm wondering how many of you check every single connector before throwing parts at it?