c/diesel-mechanics

That old timer in Flagstaff who made me watch him read a parts manual

I was 19, fresh out of diesel school, working at a shop off Route 66. This retired guy, must've been 70, came in with a Cummins 5.9 that had a weird miss. I started pulling injectors right away, but he just sat on a stool flipping through the factory manual for like 20 minutes. He pointed at a torque spec and said, 'The book tells you how, but it doesn't tell you why.' He made me re-check the valve lash first, and sure enough, that was the issue. Now I always read the theory section before I touch a wrench, and I catch more problems before they cost parts. Anybody else ever get schooled by a grumpy old-timer who turned out to be right?

2 comments

young.thomas•1d ago

My old foreman swore by breaker bars over impacts, now I get it

Back in 2019 my first foreman, Larry, would yell at us if we grabbed the impact gun for anything with more than 400 ft-lbs on it. He said impacts rattle the fastener and round off heads on seized bolts. I thought he was just old school and cranky. Then last month I had an F-550 hub nut that would not budge after 3 minutes of gun work. I finally broke out the 3/4 breaker bar with a 6 foot pipe and it popped loose with one solid yank. That was the moment I realized he wasn't being difficult, he was saving us from broken studs and wasted time. Now I only use the gun to break things loose if I know the threads are clean, otherwise it's bar and pipe first. Has anyone else had a stubborn bolt that only gave in to pure leverage after the air tools failed them?

2 comments

thea602•3d ago

The $60 ultrasonic cleaner that made me eat my words about injectors

I always figured those ultrasonic cleaners were for watch guys and jewelers, not diesel work. Last month my shop foreman in Denver made me run a set of CR injectors through one before we even talked about replacement. I was ready to call it a gimmick but after 20 minutes in the tank and a good air blowout, two of the three injectors flowed within spec on the bench. We saved the customer about $1,100 versus new parts and the truck has been running smooth for three weeks now. Has anyone else had good luck with ultrasonic cleaning on pump parts, or did I just get a lucky set?

2 comments

williamhenderson•5d ago

Had a dispatcher argue with me about idle time on a Cummins ISX last Thursday

Guy kept insisting I was wasting fuel letting a 2015 ISX warm up for 5 minutes before rolling. I asked him if he'd ever replaced a VGT actuator on one of these. Told him I'd rather burn a gallon of diesel than replace a $900 turbo because he's in a hurry. Anyone else deal with dispatch critics who don't turn wrenches?

3 comments

miles_robinson20•6d ago

Glow plug snapped off in my hand and I almost cried

I was working on a 2008 F-250 in my buddy's shop outside of Columbus last Thursday. Got the valve cover off and went to pull the glow plug on cylinder 5. It broke off flush with the head without any warning. Spent 3 hours with a extractor kit and a lot of swearing before I gave up and called a machine shop. They charged me $150 to pull it out with a welder. Has anyone else had a glow plug snap on them and found a faster way to deal with it?

2 comments

holly709•10d ago

Tried a $30 ultrasonic cleaner on injectors and it blew my mind

Picked up one of those cheap ultrasonic cleaners off Amazon last weekend for cleaning some injectors I had pulled out of a 6.7 Powerstroke. Ran them through a 10 minute cycle with some simple green and water, and the carbon just lifted right off the tips. I expected to still have to scrub them down by hand, but nope, they came out looking almost new. Has anyone else had luck with these budget units for fuel system parts, or did I just get lucky on this batch?

2 comments

the_eric•12d ago

Found the actual torque spec for injector hold-downs in a 15-year-old service bulletin

I was digging through old Cummins bulletins last night and found out the torque spec for ISX injector hold-downs was quietly updated to 96 ft-lbs back in 2008, not the 90 everyone still uses. Has anyone else run into head cracking issues from the old spec?

3 comments

mileslane•13d ago

That fuel return line crush washer trick is BS

Used to just reuse old copper washers on injector return lines like everyone at my shop in Tulsa did for years, until I had a customer come back with a miss at idle after 3 days. Now I replace every single one and torque to spec instead of just snugging them down, anyone else seen this cause intermittent issues?

3 comments

felixm29•13d ago

Old timer told me to put a penny in the fuel filter housing on a 7.3 Powerstroke

Back when I was starting out, this grizzled mechanic named Red at the shop in Rockford swore by sticking a penny in the fuel filter housing on those old Ford 7.3s to bump up fuel pressure on cold starts. I thought he was yanking my chain. Tried it on a customer's truck that wouldn't fire on a 20 degree morning. Damn thing fired right up after. Still feels wrong but it worked. Anyone else ever heard of this hack or did I just get lucky?

2 comments

wilson.olivia•13d ago

The hidden valve on fuel filters that everyone misses

I kept having prime issues after filter changes on a 2015 Freightliner until a shop foreman pointed out the tiny manual vent on top. It took me 6 months of fighting air locks to realize it was right there under the dust cover.

2 comments

jenny_lane12•14d ago

Hit 500,000 miles on my old Cummins last Tuesday

I was rolling through Flagstaff on I-40 when the odometer ticked over to half a million. That engine has never been opened up, just regular oil changes and fuel filters every 15k. Any of you guys pushed a 5.9 past 600k without a rebuild?

2 comments

fionafoster•16d ago

Tired of hearing everyone blame injectors for hard starts on 7.3s

I keep seeing guys online saying bad injectors cause hard starting on cold mornings. More often than not it's the glow plug relay or the harness going bad at the valve cover gasket. I swapped a full set of injectors on a 2000 F-350 last winter and the problem was a chafed wire under the cover. Anyone else check the simple stuff first before dropping cash on injectors?

2 comments

alice_allen5•16d ago

Switched to synthetic oil in my 6.7 Cummins at 180k miles

After running conventional for so long I saw the oil analysis come back way cleaner at 5k miles versus the old stuff at 3k. Anyone else notice a big difference in engine noise or oil life after making the switch?

2 comments

tessa_carr•17d ago

I hit 500,000 miles on my old Cummins today...

Pulled into the shop this morning and noticed the odometer rolled over to 500,000 exactly on my 1998 Dodge 2500. I've had it for about 12 years now, and it still starts up on the first crank most days. Never done a full rebuild, just regular oil changes and injectors once around 300k. Anyone else got a high mileage engine that's still going strong?

3 comments

lunar89•20d ago

Changed how I torque heads after a old-timer yelled at me at a shop in Billings

Got called out by a retired diesel guy named Walt at a parts counter last month. He saw me grabbing my torque wrench and said "you're gonna snap those studs before they even seat." Told me I was going too fast and not doing a three-pass sequence. I always thought I was careful but I was just doing one smooth pull to spec. Changed it up on a rebuild last week. Did 80 ft-lbs first, then 120, then final 150. Torque angle was dead perfect. Anyone else learn torque technique from a random guy in a parts store?

3 comments

colescott•20d ago

Saw something weird at a fleet shop in Phoenix last Tuesday

I was visiting a friend's shop out near the airport and noticed they had all their injectors laid out on a magnetic board with labels. Never seen that before, but it made pulling the right part way faster. Has anyone else tried something like that for organizing?

2 comments

the_sean•1mo ago

Went to a shop in Dallas that bragged about their "certified" techs

Stopped by a Cummins shop off I-35 last week to pick up a part. The guy out front had a sign saying all their techs were certified. But I watched one kid try to torque head bolts with a regular ratchet and a prayer. No torque wrench in sight. I asked the manager about it and he just shrugged. Anyone else run into shops that slap certifications on the wall but let people work like that?

3 comments

iris_schmidt•1mo ago

Got to poke around a truck stop garage near Bakersfield last weekend

Saw a Cummins ISX that had 890,000 miles on it with the original head gasket still holding. Have any of you seen an engine last that long without major work?

3 comments

willowr96•1mo ago

Best $92 I ever spent was on a used injector puller kit off craigslist

That cheap puller saved me from having to tow a broken down semi 80 miles back to the shop, so what's one tool you guys swear by that paid for itself the first time you used it?

3 comments

jason_stone59•1mo ago

So why does everyone treat a torque wrench like it's optional on injectors?

Last month I was over at a shop in Amarillo helping a buddy swap injectors on a 6.7 Cummins. Three different guys there told me they just 'feel it' when tightening down the hold-down bolts. One guy said he's been doing it that way for 15 years. I checked the torque on his last job with my wrench and three of six were way under spec. We're talking 5-8 ft-lbs too low on some. That's how you get injector cup leaks and copper washers failing early. Never understood why people will drop $200 on a quality torque wrench and then leave it in the box. Who else has seen a come-back job caused by guess-torquing?

3 comments

green.noah•1mo ago

Hit 100 engine rebuilds last week and it caught me off guard

I was going through my work log last Friday night, tallying up jobs from the past few years. The number 100 popped up for completed engine rebuilds, and I had to double check because it didn't feel real. I started doing them mostly on old Cummins ISX motors for a fleet out in Elmira, maybe two or three a year at first. That number just built up slowly with local farm trucks and dump trucks bringing me their tired engines. Has anyone else had a milestone like that sneak up on them where you look back and realize you've done more work than you thought?

3 comments

olivermason•1mo ago

My coolant flush machine broke down and I thought I was toast

Picked up a used coolant flush machine at auction last month for $200. Saved me tons of time on the first few jobs but the pump gave out halfway through a big fleet job last week. Had to finish flushing a dozen trucks by hand with a bucket and a hose. Cost me an extra 6 hours of labor. Has anyone else had luck fixing those pumps or should I just pony up for a new one?

3 comments

charlies37•1mo ago

Lost a whole morning on a coolant leak that was sitting right in front of me

Last Tuesday I was working on a 2015 Freightliner Cascadia at the shop here in Tucson. Spent about 3 hours chasing what I thought was a bad water pump, pulling hoses, checking the EGR cooler. Turned out it was just a loose clamp on the lower radiator hose that I tightened the day before but forgot to double check. Has anyone else had a simple fix eat up half their shift before you finally looked at the obvious spot?

3 comments

flores.emma•1mo ago

Old mechanic at a pilot in Ohio told me something that stuck

I was changing a fuel pump on a 2001 freightliner outside Columbus and this retired guy comes over, watches for a minute, then says "you're fighting the rust instead of working with the patience." He showed me how to tap the bolts a certain way with a brass punch and they came loose in half the time... has anyone else had an old timer drop a simple trick like that on you?

3 comments

evan_davis•1mo ago

Old timer at a truck stop taught me a fuel filter trick I still use

Back in 2019 I was changing a fuel filter on a Freightliner at a Flying J in Ohio and this crusty old mechanic walks over, says "you're bleeding it wrong kid." He showed me to crack the bleeder screw on the housing and crank the starter for 3 seconds instead of pumping the primer a million times. Has anyone else gotten a random tip from a stranger that actually works better than the book way?

3 comments