c/diesel-mechanics

I finally figured out why my truck kept overheating after a coolant flush

Overheard a guy at the parts counter say the thermostat gasket can swell if you use the wrong coolant. Swapped mine out with a new one last Wednesday and the temp gauge has been dead center ever since. Anyone else had this happen with a certain brand of coolant?

Just did the math on injector rebuilds vs. buying new

I figured out I could rebuild six injectors for what one new one costs, $240 at the shop down on Main. Saw a YouTube video from a guy in Texas that broke down the whole process, ever tried it yourself?

Had a chat with an old fleet mechanic last week and he said something about DEF that stuck with me

Cat vs Cummins: I ran both injector setups back to back on the same 3406E

Ngl I spent 8 months running Cat injectors in my 3406E and swapped to Cummins CELEA injectors last Tuesday. The Cat ones just don't hold up past 300k miles without losing pressure. After the swap I gained 2 MPG on my Pete hauling logs out of Eugene. The CELEA injectors also cut my idle smoke by half. Has anyone else tested this swap on a 3406E without changing the ECM calibration?

Found my old master cylinder from 1987 under the workbench

I was cleaning out the shop last week and stumbled across a master cylinder I pulled off a Freightliner back in '87, still sitting in a dusty box. That thing was all metal and rebuildable, not like the plastic junk we get now from the parts houses where you just throw the whole unit away. Does anyone else save old parts just to remember how much simpler this trade used to be?

PSA: A bad injector return line took me 4 hours yesterday

Thought I had a low compression issue on a 7.3 Powerstroke, chasing IPR duty cycles and buzz tests for 3 hours. Turned out to be a tiny pinhole in a return line spitting fuel at the connector. Anybody else waste a whole afternoon on a $6 piece of hose?

Unpopular opinion: Rebuilt injectors are just as good as new ones... or not?

My '02 Cummins started running rough last week, so I pulled the injectors. One was shot, bad enough to make it idle like a tractor. I was set on buying new ones at $400 each, but the local shop I trust said to go with rebuilt for $180 each. They promised they flow-test them and replace the tips... but I keep thinking about that one guy on here who said rebuilt ruined his motor after 2,000 miles. Has anyone else tried rebuilt vs. new on a high-mileage truck? Did yours hold up or did you regret it?

Question about rebuilding injectors versus buying remanufactured sets

We got a fleet of old Cummins ISX motors at our shop outside Nashville. Last month I spent 4 hours rebuilding a set of injectors for a 2013 Pete 386, only to have one fail the pop test on the bench. I swore off rebuilding after that and told my boss we should just buy reman sets instead. But the shop foreman says rebuilding is cheaper if you know what you're doing and have the right tools. What do you guys do when a set of injectors needs attention, tear em down or swap em out? I'm leaning toward reman after that wasted day but I'm open to hearing the other side.

Swapped from a cheap torque wrench to a Snap-on and my head bolt torque readings finally make sense

I was chasing head gasket leaks for three months on a 6.7 Cummins, and the cheap Harbor Freight wrench was off by 25 ft-lbs at 200. The Snap-on was pricey at $400, but after one job the coolant stayin' in the block. Anyone else seen big swings between budget and pro torque tools on their builds?

Stuck on a job in Lubbock because I forgot my torque wrench

I drove 4 hours to Lubbock last Tuesday to do a head gasket swap on a Freightliner and realized I left my torque wrench at the shop. Had to borrow one from a local guy and it wasn't even close to calibrated right. Cost me an extra 3 hours of work and a lot of cussing. Anyone else had a tool screw up their whole day like that?

I used to tell guys to always replace injectors in sets of 6, but a CAT rep in Nashville talked me out of it last month.

He showed me data on a 3406B where mixing a single new with five old ones actually held better flow balance because the ECM could compensate easier. Has anyone else run into this or am I just late to the party?

Old timer at a job site in 2008 told me to always torque injector lines by feel, not with a wrench

I followed his advice for years until a line cracked on a 6.0 Powerstroke last winter, cost me $400 and a full weekend to fix, what do you guys use for torque spec on those old Navistar lines?

Drove 3 hours to a shop in Bakersfield and watched a guy fix a 6.7 Powerstroke with a zip tie...

Had a week where every engine I touched fought back

Three jobs in a row last Tuesday through Friday. First was a Cummins ISX in a Freightliner that wouldn't hold oil pressure. Spent half a day chasing it, turned out to be a stuck piston cooling nozzle. Then a Cat C15 with a miss that ended up being a rocker bridge that cracked in half. Then on Friday a Powerstroke 6.0 that needed head gaskets, which I knew going in, but two of the head bolts snapped off in the block. Took me into Saturday night to extract them. Anyone else have a stretch like that where nothing goes smooth?

Three day stretch last month nearly made me quit diesel work.

Lost a Cummins ISX to a dropped valve on a Monday, then a DEF system threw a code that took 14 hours to trace on Tuesday. Wednesday had a customer argue my $850 quote was too high for an injector swap. Anyone else have weeks that make you question this trade?

PSA: That conversation with my old instructor finally clicked after 5 years

Was talking to my diesel instructor from tech school last week about a truck that kept losing power uphill. He said I was probably chasing sensors when the real problem was rail pressure dropping from a worn pump. I always thought he was just old school and out of date but the guy was right, I found a cracked plunger in the CP3. Has anyone else had a past teacher or mentor say something that nagged at you for years before it finally made sense?

Vent: Found out my torque wrench was off by 40 ft-lbs for 2 years

I was doing a head gasket job on a Cummins ISX last week and kept second guessing myself because the torque felt wrong. So I finally went and borrowed my buddy's Snap-on digital torque adapter to check my old Precision Instruments wrench. Turns out it was reading 40 ft-lbs low on anything over 200 ft-lbs. I've been using that wrench since I started at this dealer in 2022 for every main cap and rod bolt. That means I've been under-torquing critical fasteners on probably 30 plus rebuilds. I found the calibration sticker and it expired in 2021, never even thought to look. Now I gotta figure out if I should call those customers back or just hope nothing grenades. Anyone else ever trust a wrench too long without checking it?

Was dead wrong about synthetic oil in my old Cummins

I spent 15 years swearing conventional Rotella was the only thing that belonged in a 12-valve. Buddy at the shop kept pushing synthetic, said I was leaving power on the table. Finally tried it after I pulled a pan full of sludge at 350k miles. Six months later my oil analysis came back cleaner than ever and I gained 2 psi oil pressure hot idle. Any of you guys made the switch on a high-mileage engine and seen real results?

Chatting with an old fleet mechanic changed how I look at oil analysis

Was at a parts counter in Tulsa last Tuesday and this guy in his 70s starts explaining how he caught a failing bearing through oil samples 6 months before it let go. Said he never waited for the lab report to confirm what he already suspected from the smell and texture. Any of you guys run extra checks on your oil yourself before sending it off?

That common glow plug replacement mistake that bit me (and probably you too)

So I was helping a buddy swap glow plugs on his 7.3 Powerstroke last weekend, and he kept saying the new ones were too loose going in. I looked closer and realized he was putting the wrong ones in for the application. He had bought the longer ones meant for a different head design, and they were bottoming out before they even seated. I told him to stop right there, because I've seen guys crank those down anyway and snap them off inside the pre-chamber. That's a nightmare to extract, and it can ruin your whole weekend. We ended up having to order the shorter ones from the parts store, and they cost like $40 more but at least they fit. Has anyone else dealt with mixing up the two different glow plug lengths on these older Fords?

Tried a fuel additive on my old Cummins and got a surprise

I threw some of that popular diesel injector cleaner in my 2002 Ram 3500 last week, figured it couldn't hurt. After driving about 200 miles, my rough idle totally smoothed out, and I swear the acceleration felt snappier. I checked the fuel filter after and it had way less gunk than usual, so maybe it actually broke stuff loose. Has anyone else seen real results from these additives, or was it just placebo on my end?

Question about those injector cleaning machines everyone swears by

I spent 3 years telling guys at the shop that those ultrasonic injector cleaners were a waste of cash. Finally broke down and bought a used one from a shop in Cleveland for $400 when nothing else would fix a rough idle on a 6.7 Powerstroke. Two cycles through that machine and the truck ran smoother than it had in years. Has anyone else had a tool they were dead wrong about that actually saved their bacon?

Had a talk with an old timer at the shop that made me rethink my whole approach to injectors

I was swapping out a set of injectors on a 6.7 Cummins last Tuesday and this guy in his 70s walked by and asked why I was replacing them instead of pulling them to test first. He said he's seen guys toss 800 bucks at new injectors when the real problem was a bad fuel pump starving them or a wiring issue. It hit me different because I've been doing this for 10 years and never once questioned if the new part was even needed. Anybody else ever get schooled by someone twice your age on something you thought you had down?

Stopped by an old Cummins shop outside Raleigh last week...

Walked in and the place still had those paper rosters on the wall from the 80s. They had three mechanics running five bays... nobody under 50 years old working there. Makes me wonder where all the young guys are going.

Last month I finally got why old school guys swear by straight weight oil

I've been running 15w-40 in everything for years, but last month a retired fleet mechanic in Tulsa said I was wasting money on a 6.0 Powerstroke that's already got 280k on it. He showed me how much blowby was getting past the rings with multigrade and said straight 30 weight would seal it better. Has anyone else switched to straight weight on a high mile engine and seen a difference?