c/diesel-mechanics

Visited a shop near Nashville and their air compressor setup was a total mess

I stopped by a little diesel shop outside Nashville last week to grab a part for a 6.7 Cummins I'm working on. Walked in and saw their air compressor was sitting right next to a wall with zero ventilation. The tank had rust dripping from the drain valve too (like, actual orange streaks). I asked the guy about it and he just shrugged and said "it's always been there." Anyone else run into shops that totally ignore basic air compressor maintenance and floor layout?

I finally threw away $400 on a reman injector that was dead out of the box

Ordered a reman injector for a 6.7 Cummins off some online parts place last month. Got it in, swapped it in on a Saturday thinking I'd save time. Truck wouldn't start, sputtered like crazy. Took me three hours of chasing wires and checking fuel pressure before I tested the injector itself. Turns out it was bad from the start. Anyone else had a reman part show up DOA and waste a whole day? Feels like it's happening more and more.

Question about using starter fluid on a cold Detroit 60 series

I always thought a quick shot of ether was fine for starting a cold 14 liter. A older guy at the shop showed me glow plugs warm up the intake air enough that you don't need it, and I toasted a glow plug relay last winter trying anyway. Anyone else stop using starter fluid after seeing what it does to the preheat system?

Called BS on injector cleaning services until I pulled a set off a 6.7 Powerstroke last Tuesday

Guy comes in complaining about rough idle and loss of power. I figured it was a bad injector or two. Pulled them and they were caked in carbon. Sent them to a shop that does the ultrasonic cleaning and flow testing. $45 each. Put em back in and the thing runs smooth as silk. Been a diesel guy for 12 years and always thought cleaning was a scam. Guess I was wrong. Anyone else had luck with this or was it just a fluke?

That one Wednesday where a coolant leak led me to a cracked head on a 6.7 Powerstroke before it blew

I caught it because the truck had been sitting for two days and there was a tiny puddle under the fan shroud, not the radiator, so I pressure tested it and found a hairline crack between cylinders 5 and 6.

Had to pick between an OEM injector and a reman one today

Went with the reman to save $400 on this 6.7 Powerstroke job. Now it's got a slight knock at idle and I'm wondering if I screwed up. Anyone else take the cheap route and regret it?

Shoutout to the guy who showed me the grease gun trick on a stuck U-joint

Honestly, last Wednesday was shaping up to be a nightmare. I was underneath a 2015 Freightliner Cascadia trying to get a seized U-joint off the driveshaft, and nothing was budging. I'd been at it for over an hour, heat, breaker bar, the whole deal, and my arms were shot. This older mechanic from the bay next door walks over and goes 'try pumping grease into the zerk fitting till it pops the cap.' I laughed at first, but Ngl, after I hooked up the grease gun and pumped about four good shots, that cap popped right off with a little tap. I spent the next 20 minutes just shaking my head thinking about all the time I wasted on these things before. Has anyone else found a weird trick like that that just saves your whole day?

Heard a guy at the parts counter say he never uses torque wrenches on intake manifolds

I was picking up oil filters this morning and overheard this older mechanic telling the parts guy he just tightens them by feel. No torque wrench ever. I dont know why that stuck with me but it made me think about how many things I do by the book when maybe I dont need to. Still gonna use mine on head bolts though lmao. Has anyone else picked up little shortcuts like that from just being around the shop?

Swapped out my hydraulic pump for a cheaper brand and regretted it immediately

I compared a Parker pump to a no-name knockoff on a 2005 Peterbilt last month and the difference was night and day. The knockoff started whining after about 60 hours of run time, while the Parker one I replaced had lasted 4 years without a peep. What kind of luck have you guys had with aftermarket vs OEM hydraulics?

Old timer in Memphis called me out on my valve lash technique

I spent like 3 years doing valve lash adjustments the way I was taught at tech school. Then this grizzled old diesel mechanic at a shop in Memphis watched me for 30 seconds and said 'you're leaving half a turn on the table every time.' He showed me how to feel for the exact spot instead of just going by torque specs. Tried his method on a 2007 Peterbilt last week and the engine ran smoother than it ever has. Now I'm questioning everything else I learned on a textbook lol. Has anyone else had some old school dude completely change how you do a basic job?

Why does everybody skip checking the injector return lines?

I swear I keep pulling into shops behind other mechanics who just replaced injectors on a 6.0 Powerstroke and the truck is still running like garbage. I had a guy in Denver last month bring me a 2005 F-350 that three different guys already worked on. They all put in new injectors but never bothered to look at the return line crossover tube. That stupid plastic T-fitting was cracked and leaking fuel pressure back to the tank. I replaced that $15 part and the truck ran perfect. How come nobody talks about this stuff? Has anyone else dealt with a simple return line issue that everyone else overlooked?

Switched to synthetic oil after seeing the internals of a 7.3 Powerstroke

A buddy tore down his '02 Ford with 250k miles on conventional oil and the sludge was bad. I looked at a similar motor that ran synthetic its whole life and the difference in the valvetrain was night and day. Anyone else see enough proof to make the switch?

Hot take: Those ultrasonic injector cleaners are not a gimmick

I ran a set of older Cummins injectors through a cheap ultrasonic cleaner I got on Amazon for $120 after a buddy swore by it. The difference in spray pattern before and after was night and day, and the truck actually stopped smoking at idle. Anyone else have results that surprised them from something they thought was snake oil?

My old mentor told me I was ruining injectors by not pre-lubing them

A couple years back, my old diesel mentor Dave watched me slap a set of injectors into a 6.0 Powerstroke without oiling the o-rings first. He pulled me aside and said 'you're dry firing those seals, they'll leak in 5,000 miles' - and he was right. After that, I started using a thin coat of clean 15W-40 on every injector install and seal replacement, and I haven't had a single comebacker since. Anybody else have a simple habit like that that made a huge difference in your failure rate?

Why does nobody talk about how injector tips wear down slowly over time?

I work at a shop in Phoenix and I pulled a set of injectors out of a 2015 Freightliner last month that had 400k miles on them. The tips looked fine from a glance but when I compared them to a brand new set under a magnifying glass the difference was crazy. The orifices had gotten about 15% larger from all the fuel flow and wear. Has anyone else noticed this gradual change causing weird misfire codes that come and go?

Hit 500,000 miles on my work truck last week and I'm still shocked

I rolled over 500,000 miles on my 2002 Ford F-350 with the 7.3 Powerstroke last Tuesday. Got it from a guy in Austin who had already put 300k on it doing hauling gigs. I've been using it for my landscaping company for the last 6 years pulling dump trailers and skid steers. The thing still starts up every morning without any glow plug drama and I've only had to do basic maintenance like injectors and a water pump. The big surprise was that the original transmission finally gave out at 482k, which I thought was pretty good for a stock unit. What kind of high mileage numbers have you guys seen on your shop trucks or personal rigs?

Just figured out why my high-pressure oil pump kept failing

I used to just throw a new pump on whenever I lost pressure in a Powerstroke, thinking the part was junk. Then a guy in Toledo showed me his trick after I swapped my third pump in 8 months, checking the IPR screen for debris. Turns out I was missing a clogged screen every time, which starved the new pump. Now I always pull and inspect that screen first, saves me $400 a pop. Any of you guys run into this on the 6.0L?

Took me 3 injector swaps to realize I was overtorquing the hold-down bolts every time

An old journeyman at the shop glanced at my torque wrench and said 'you're tightening those cold, aren't you?' and I finally understood why I kept snapping bolts on the rear cylinder.

Stop buying cheap fuel filters from that auto parts chain on Route 9

I grabbed a bargain bin filter for my Cummins there last Tuesday and found plastic shavings in the housing when I swapped it out two days later, has anyone else run into junk like this from those stores?

Talked to an old Cummins guy at a parts counter last week and he made me rethink everything about how I clean injectors

Warning: Found out my injector cups were off by 0.002 inches

I was pulling injectors on a 2008 Cummins ISX in Atlanta last Tuesday and decided to mic the cups before slapping new ones in. Turns out two of them were out of round by 0.002", which is basically nothing but the manual says it'll kill the seal. Anyone else ever find stuff that's technically within spec but still causes issues down the road?

PSA: Cold air intakes on big rigs - hype or real gains?

I was convinced aftermarket CAIs were just noise makers for pickup guys, but a buddy documented a 2 MPG improvement on his Freightliner Cascadia after 6 months of data logging. Has anyone else seen actual fuel savings from one, or was that just a lucky fluke?

Old timer changed my mind about block heaters yesterday

I've always been the type to just let a cold engine crank and crank until it fires up. Figured block heaters were for guys up in Canada or something. But yesterday I was helping this retired mechanic named Frank with a Cummins swap and he asked if I always beat on my starter like that. He said every cold start without a block heater is like grinding 500 miles off your starter and battery life. Then he showed me his old work truck with 400k miles on the original starter and he always used a timer to plug it in two hours before start. I never thought about the math that way. It hit different hearing it from a guy who's been doing this since the 70s and still has all his original tools. Anyone else have an old timer talk sense into you about something you always thought was unnecessary?

That $200 coolant flush kit that did nothing but leak

Picked up one of those fancy coolant flush kits last month from a parts store in Spokane. Cost me $200 and I spent 4 hours under my F-750 trying to get it to seal right. Ended up dumping half the coolant on my garage floor and the stupid thing still leaked. Went back to the old garden hose trick and it worked perfect in 20 minutes. Anyone else waste money on a tool that just made things worse?

That one Tuesday last month when three trucks showed up with the same exact problem

I swear it was like the universe was testing me. Three Freightliner Cascadias all came in on the same day with the DEF system throwing the exact same code (P204F if you're curious). First one took me 4 hours to diagnose, second one I did in 90 minutes, third one I knocked out in 45. The common culprit? A $12 plastic fitting that cracks right where it connects to the pump. Just a heads up if you start seeing that code pop up more often. Has anyone else noticed a weird pattern with certain issues hitting in waves like that?