c/diesel-mechanics

Just realized I've been torquing head bolts the hard way for 3 years

Last week I was helping a buddy swap a head gasket on his 7.3 Powerstroke out in his garage near Tulsa. I grabbed my torque wrench and started doing the bolts in a simple circle pattern like I always did. He stopped me and said I was asking for a warped head doing it that way. He showed me the proper criss-cross sequence from the center out, working in stages. I felt like an idiot because I've been working on diesels for over a decade and nobody ever corrected me. Tried his method on the reassembly and the head sat way flatter when I checked with a straightedge. Has anyone else picked up a basic habit wrong for years and only learned the right way from someone calling you out?

Vent: Just had a fleet truck come in with oil pan full of coolant from a bad EGR cooler install

This 2015 Freightliner Cascadia came in last Wednesday with a milky oil sample from the last service. The shop before me put a cheap aftermarket EGR cooler in about 6 months ago and didn't torque the coolant line clamps down right. It leaked slowly for months until the cooler cracked from the stress. Now the whole oil system is contaminated and the guy is looking at a $4,000 rebuild. I keep seeing these trucks come in with the same problem from guys skipping the proper alignment steps on the EGR cooler bracket. Am I the only one who takes the extra 20 minutes to check the torque specs and bracket fitment on these trucks?

After 10 years, I finally switched from conventional oil to synthetic in my old Cummins and I was wrong about it being a waste

I used to argue with guys at the shop all the time that synthetic oil was just marketing hype for guys with too much money. Been running Rotella 15w40 in my 5.9 for over a decade with no issues. Then last winter when temps dropped to -15 in Denver, my truck sat for three days and I had to wait 20 minutes with block heater just to crank it over. Buddy told me to try Rotella T6 synthetic and I figured what's it gonna hurt. After that change, started right up at 5 degrees with no block heater. Oil pressure is more stable now too, sits at 40 psi at idle hot instead of bouncing between 30 and 35. I still think conventional is fine for most people who run their trucks daily in warm climates but for anyone dealing with cold starts, synthetic actually made a real difference for me. Anyone else have that moment where they had to eat their words about engine oil?

PSA: Always check your oil cooler lines before a long haul

I changed my mind about skipping routine checks on oil cooler lines after blowing one on I-80 outside of Des Moines last Thursday. I was hauling a load of lumber and saw the oil pressure gauge drop from 50 to 20 psi in about 30 seconds. Pulled over and found a chafed line that had been rubbing against a bracket for weeks. It cost me $350 for a tow and a replacement line at a shop in Newton, plus I lost a full day on delivery. Now I do a quick visual on those lines every time I fuel up. Has anyone else had a hidden chafe point wreck their run like that?

Put a fresh set of injectors in a 7.3 Powerstroke last Tuesday and got way worse fuel economy than before.

Old injectors were original at 280k miles. New ones are from a reputable brand not cheap eBay junk. Truck ran smoother idled quieter but my mpg dropped from 17 to 13 on the highway. Talked to a guy at the parts counter and he said new injectors need a good 500 miles to break in and the ECM has to relearn the trim. That sound right or did I get a bad set? Anyone else seen this after swapping injectors?

Stop using brake cleaner on injector seals. I keep seeing it.

Was helping a guy in Denver last week diagnose a rough idle on a Cummins ISX. He soaked the new injector seals in brake parts cleaner before install. Said his old boss showed him that trick. I told him to stop right there. That stuff eats the rubber coating on the copper seals over time. Seen three trucks in the last year blow out injector cups because of this. The seal swells up from the chemical and then fails under high pressure. Anybody else run into this or am I the only one yelling about it?

Pro tip: If you're fighting a water in fuel issue, check the tank pickup screen first

Last week I spent 3 hours chasing a random stall on a 2015 Freightliner. Changed filters, drained the separator twice, still had issues. Finally pulled the tank sender and found the pickup screen was clogged with algae slime. Cleaned that out with brake cleaner and a small brush, truck ran perfect after that. Anybody else run into this or do you usually just replace the whole sender unit?

Saw a guy use a Harbor Freight ratchet strap as a timing belt replacement on a 7.3 in a dirt lot off I-40 last Tuesday

He said 'it'll hold till I get home' and I just stood there wondering if I should help or just watch the show. Has anyone else seen a field fix that actually worked or totally blew up?

Remember when you had to use a torch to break loose rusted bolts?

I was under a 2015 Freightliner yesterday and got reminded how nice impact wrenches are. Back in the early 2000s when I started, I'd spend 20 minutes heating up a bolt on a semi frame just to get it moving. Now I just hit it with my Milwaukee M18 and it's off in 5 seconds. Anyone else glad we moved past all that torch work?

Water pump went out on a 6.7 Powerstroke near Flagstaff last Tuesday

Was hauling a 12k trailer through the mountains and heard the belt start chirping. Pulled over at a Love's in Flagstaff and the water pump was leaking coolant from the weep hole bad. Took 4 hours to swap it in the parking lot with basic tools, definitely gonna keep a spare pump and thermostat in my truck now. Anyone else carry backup parts for their work truck?

I finally walked into a truck stop in Bakersfield and saw something that made me laugh

So I stopped at this big Pilot off the 99 last week to grab a coffee and stretch my legs. I noticed this one mechanic had parked his rig right near the fuel island and left his hood propped open, like he was doing some kind of quick fix. But then I got closer and saw he had rigged up a bungee cord to hold a shop light under the hood, and the light was duct taped to a half-empty water jug for balance. I mean, it worked, but it looked like a total disaster waiting to happen. I stood there for a minute wondering how many times that thing had fallen on his face. Has anyone else seen some truly wild field repair setups that just make you shake your head?

Can we talk about how often people forget to prime fuel filters on the big rigs?

I swear I see it at least once a month at the shop in Tulsa. Some guy slaps a new filter on a Cummins ISX, fires it up, and then wonders why it's cranking forever and throwing air in the system. Takes 30 seconds to fill it with diesel from a clean jug. Why do people skip this?

Used to torque every head bolt by hand till my arm gave out, now I just use a torque wrench on a 1/2 impact for the rough pass

About 2 years ago I was doing a Cummins ISX head gasket in a Freightliner and my arm just cramped up halfway through the torque sequence. Took me an extra 45 minutes fighting that thing. My buddy Mike saw me and laughed, said why dont you just zip em down with the impact to 90 ft-lbs then finish with the wrench. Tried it on the next job and it cut my time in half, no issues with the stretch either. Anyone else do this or am I asking for trouble on the final torque check?

Realized how much diagnostics changed when I found my old Snap-on scanner from 2008

I was cleaning out my toolbox last weekend and found my old Snap-on Modis from way back. That thing was a tank back then, but now it just sits there lol. Last month I was working on a 2023 Freightliner with a DEF issue and my new Autel tablet found the problem in 10 minutes. Three years ago I would have spent an hour chasing wires with a multimeter. The old Modis could barely read half the modules on that truck. Anyone else hold onto old scanners for nostalgia or just me?

Water pump blew on my 6.7 Powerstroke halfway through a job in Nashville last Friday

Spent $450 on a used injection pump and it saved my old Cummins

My 12-valve started running rough last month and I figured it was the lift pump again. But after chasing fuel pressure for two days, a buddy at the shop said check the injection pump timing. I found one off a wrecked truck for $450 and swapped it in over a weekend. It fired right up and smoothed out completely - no more hunting at idle. Has anyone else had luck with used pumps or do you always go reman?

Had to pick between saving an old 12-valve or swapping in a common-rail

Pulled a 1997 12-valve Cummins out of a wrecked Ram 2500 last month, engine had 340k miles but ran like a top. I was torn between rebuilding that old mechanical engine or just finding a used common-rail for the project truck. I went with the 12-valve because I know those P-pumps inside out and parts are cheap, plus no wiring headaches. After I got the injection pump timed it fired right up - who else has stuck with the old stuff over the newer computer controlled diesels?

Hit 500 injector replacements last week without even realizing it

I was just tallying up my job logs for the year and saw I hit 500 injector swaps. That number caught me off guard since I mostly work on 6.7 Powerstrokes at a shop in Tulsa. Anyone else keep track of how many of a specific job they've done without meaning to?

Rant: Took me 3 tries to figure out a simple injector tick on a 2015 Cummins

Wasted 6 hours last month chasing a fuel pressure issue on a Ram 2500, swapped filters twice and pulled the pump before I noticed the #4 injector return line fitting was barely cracked, has anyone else had a fitting that looked tight but was actually loose?

Can we talk about injector cups that refuse to come out

Last month I was working on a 2015 Freightliner Cascadia out in Odessa, Texas and those injector cups were like welded in place. I spent a solid 3 hours just trying to get the first one loose with my slide hammer and it barely budged. Finally I had to bust out the torch and heat the head up to 400 degrees before it even thought about moving. My coworker Dave just stood there laughing saying I shoulda used Kroil overnight but I didn't have that kind of time. The whole job that should've taken 5 hours turned into a 9 hour nightmare because of three stuck cups. Has anyone else had luck with a specific method for removing stubborn injector cups without damaging the cylinder head?

I used to laugh at guys who swore by infrared temp guns for diagnostics

Been wrenching on diesels for about 8 years now and always thought those cheap IR guns were a gimmick. My old mentor would just feel hoses and manifolds with his bare hand after a cold start and he was never wrong. But last month I had a 2016 Freightliner Cascadia with an intermittent EGT issue that had me chasing my tail for two days straight. Finally borrowed a buddy's IR thermometer, pointed it at each runner on the exhaust manifold, and found a 150 degree difference between cylinder 3 and 4 in under 10 seconds. Turned out to be a clogged injector dumping raw fuel. That little $35 tool saved me probably 6 more hours of guessing. Has anyone else had a cheap diagnostic tool prove them totally wrong?

Blown a head gasket on a Detroit 60 in 117 degree heat outside Barstow

Last summer I was hauling a load of produce through the Mojave and my series 60 started puking coolant near Barstow. Pulled over and saw the head gasket was shot, oil looked like a milkshake lol. Had to wait 8 hours for a tow to a shop that could even fit me in. Anyone else had a hot weather failure like that on a highway run?

Finally fixed a leak on a Series 60 without pulling the head

I had to choose between trying a stethoscope and just replacing the fuel lines one by one. Went with the stethoscope first because I didn't want to waste $80 on new lines that might not fix it. Found the leak at the number 5 injector return line in about 10 minutes. Turns out it was just a cracked ferrule, cost me $3 at the parts store. Has anyone else had luck with those cheap mechanic stethoscopes or am I just getting lucky?

Man, the week I had to rebuild a 6.0 Powerstroke in a dirt driveway back in 2019

I still remember that stretch in July, temps hit 97 every day. Guy rolled up with his work van, 150k miles, said it started fine but after 20 minutes it would lose all power and blow white smoke. I knew it was a high pressure oil leak before I even popped the hood, that old 6.0 curse. Pulled the stand pipe and dummy plug on the passenger side and found the o-ring had just sheared clean off. The kicker was I had to do it all in his gravel driveway with no shade, just me and a cheap harbor freight socket set. Took me three days start to finish because I had to keep stopping to cool off and drink water. At the end he paid me $800 cash and said I saved his business, because the dealer quoted him $4k. Felt good but man my back hated me for a week after. Has anyone else here gotten stuck doing a big job in some crappy spot with no lift?

Shoutout to the guy who told me my injector timing was off by 3 degrees

I was in Green Bay last fall working on a DT466 and this old school mechanic just watched me for a minute. He goes "son, you're chasing a ghost if you don't check the timing first." I always just threw injectors in and hoped for the best but now I break out the dial indicator every single time. Has anyone else had a simple tip from a stranger save them hours of headache?