c/diesel-mechanics

Debate: is a full engine rebuild always better than swapping in a used long block?

Last month in Nashville I spent 6 days overhauling a DT466 only to find the crank was scored, but a buddy down the street did a junkyard swap in 3 days and his truck is running fine so which option actually saves you time and money in the real world?

Rant: That aftermarket injector swap that grenaded my #6 cylinder

Put a set of cheap injectors in a Freightliner last Wednesday to save the customer some cash. By Friday afternoon #6 piston had a hole in it and oil was pissing out the dipstick tube. Anyone else swear off anything that isn't OEM or Bosch reman after a blowup like this?

Vent: Fell for that 'miracle in a bottle' fuel additive scam last month

Dropped $80 on a bottle of some snake oil additive that promised to clean my injectors and save me on fuel costs but all it did was clog my fuel filter and leave me stranded on I-35 for two hours waiting for a tow, has anyone else had this happen with those miracle additives?

Ran across a stat that blew my mind about injector cleaning

I was looking up some stuff on the Bosch website last night and found out that a 2% injector flow loss can drop your fuel economy by over 5%. That seems tiny but adds up fast. I always thought a little clog here or there was no big deal. Has anyone else seen numbers like this from their own testing?

Old timer told me to use gear oil on cylinder heads, almost cost me an engine

Had a retired mechanic named Frank at the shop in Pittsburgh tell me to slather gear oil on cylinder head bolts for better torque. I figured he'd been doing it 40 years so he must know his stuff. Put a 6.0 Powerstroke together that way and two weeks later the head gasket blew out on a delivery truck. Turns out gear oil can hydro-lock the threads and mess with your torque readings. Frank meant well but I lost 12 hours of work and 200 bucks in gaskets. Any of you guys had bad advice from someone you trusted?

Had to pick between a rebuilt injector or a new one on a 6.0 Powerstroke last month

I went with the new one even though it cost $120 more, and the truck finally stopped smoking on cold starts. Has anyone else seen rebuilt injectors fail faster than new ones?

Hit 200 engine rebuilds this week and still can't believe it

Ngl, I was just counting up my logbook for tax stuff and realized I've done 200 full diesel engine rebuilds since 2018. That number surprised me because most of those were in a two bay shop in Bakersfield with no lift, just a floor jack and some sweat. The first one I did was a 5.9 Cummins in an old Dodge and I damn near stripped a main cap bolt. Has anyone else kept track of their rebuild count or is that just me being weird?

Finally tried my buddy's way of bleeding injectors instead of the book method

I was fighting a bad miss on a 2002 7.3 Powerstroke last Tuesday and spent like 3 hours following the service manual step by step. My buddy Dave stopped by and showed me his trick of cracking the lines at the injector while having someone crank it over instead of using the Schrader valve method. He had that thing running smooth in under 20 minutes, no joke. Now I'm wondering if I've been wasting time on every single diesel I've worked on for the past 5 years. Anyone else ditch the manual way for something a veteran taught you that just flat out works better?

Oil change intervals - are we all following the manufacturer or going by feel?

I've been turning wrenches on diesel trucks for about 12 years now, and I keep seeing guys at the shop argue about oil change intervals like it's a religion. On one side you got the sticklers who say follow the OEM manual to the letter, like 15,000 miles on synthetic or whatever the book says. Then you got the old school guys who swear by 5,000 miles no matter what, even with modern oils and filtration. I had a customer last week with a 2019 Cummins who was dead set on 3,000 mile changes, and I tried to explain he's wasting money and oil, but he wouldn't budge. But I also had a guy with a 2015 Duramax run 20,000 miles on the same Rotella T6 and his oil analysis came back clean. So which side are you on? Do you trust the engineering or go with the 'better safe than sorry' mindset, and have you ever seen an engine fail from stretching it too far?

Pro tip: check your lift pump before you throw parts at a no-start

Spent 3 days chasing a crank no-start on a 2005 Duramax last month. Swapped injectors, new CP3, even had the ECM flashed before I finally tested the FASS pump at idle and saw 4 psi instead of 15. Anyone else get burned by a dying lift pump that still whined like it was fine?

Old timer laughed at me for using a torque wrench on oil drain plugs

Was in Billings, Montana helping a guy with his Freightliner and he literally swatted my hand away, saying "son that plug ain't a spaceship part." He hand-tightened it with a cheater bar and it never leaked - has anyone else run into old-school guys who think torque wrenches are a waste on routine stuff?

Wasted 12 hours on a cylinder head gasket job thanks to the wrong torque wrench

Last month I spent an entire Saturday wrestling with a Cummins ISX head gasket, only to find out my cheap torque wrench was off by 40 foot-pounds. Leaked coolant everywhere on the test drive, and I had to pull it all apart again. The $75 tool cost me a full weekend and an extra $30 in gaskets and fluids. Has anyone else been burned by a budget torque wrench that wasn't calibrated right?

Had a coolant hose burst on me in the middle of a 3 AM tow on I-80

I was hauling a broken down dump truck back to the yard near Des Moines when the lower radiator hose let go. Steam was pouring out so thick I couldn't see the dash, and I ended up pulling over on a gravel shoulder with no cell service. Had to patch it with a roll of electrical tape and a Gatorade bottle to make it the last 15 miles - got me thinking, what's the weirdest field fix anyone else has had to pull off?

The ongoing fight over how often to change fuel filters on older Cummins engines

I keep seeing guys online saying change your fuel filter every 15,000 miles on a 5.9 Cummins, but then the old timers at my shop in Ohio swear by 30,000 miles and say the extra filtering just makes the injection pump rely on new filters too much. My own 2001 Dodge with 280k miles ran fine on a 20k mile schedule for years until I stretched it to 32k and got stalling on a grade. So what's the real sweet spot for ISB engines that see highway and towing, not just light duty?

Pro tip: Loosen the fan belt before you try to torque the harmonic balancer bolt

Was helping a buddy swap an engine on a 1995 F-250 at his shop in Billings last Saturday. Spent 45 minutes fighting that bolt before I realized the belt was tensioned and holding the pulley. Has anyone else figured out a faster way to break those bolts loose on a tight engine bay?

That talk with a old fleet mechanic really got me thinking...

I was swapping a injector on a 2015 Kenworth last Thursday and this guy Bobby who's been turning wrenches since the 80s walked over. He flat out told me I was wasting time chasing electronic faults when 90% of his problems get solved by checking grounds and harness rubs first. He showed me three trucks where I spent hours on scan tools and the fix was just a chafed wire behind the firewall. It hit me different because here I am relying on laptops and he's just looking at the truck and finding stuff in 20 minutes. Any of you old school guys got a habit that saves you time that newer techs miss?

Honestly the difference between a 2-stage and single-stage air dryer on a truck after 6 months is night and day

I found a bypass trick for a stuck HEUI injector that actually worked... or did it?

I was working on a 7.3L Powerstroke that wouldn't start, fuel return was normal, and ICP was reading low. I tried the old unplug the ICP sensor trick and no change. Then I read about swapping the IPR valve with a known good one from a running truck, which I did from a buddy's 2002 model, and it fired right up. But now I'm wondering if that was just coincidence or if swapping parts like that is a legit diagnostic shortcut. What's your take on this kind of swap test, does it prove the part was bad or just hide the real problem?

Blew $600 on a reman injector set that barely lasted 6 months

I bought a set of reman injectors off eBay back in January for my 6.0 Ford. Saved about half compared to new ones from Ford. By July three of them started sticking and I had to pull everything apart again. The labor alone cost me more than if I just bought new injectors the first time. Has anyone else had bad luck with reman parts from certain sellers?

Not convinced CAT filters are worth the premium anymore

I swung by a fleet maintenance yard in Tulsa last month and saw three 15-liter engines running nothing but Wix filters for over 200k miles. The oil analysis came back cleaner than any CAT filter I've ever pulled. Has anyone else switched brands and seen better results?

That day a freeze plug let go on I-40 outside Nashville

Last winter I was hauling a load of produce east on I-40 when the temperature dropped fast. Around mile marker 210 near Nashville, my old Freightliner started running rough and blowing white smoke. Pulled over at a rest stop and popped the hood to find a frost plug had popped clean out of the block. That let all the coolant drain out onto the asphalt in under a minute. I had to call a local wrecker to tow me to a shop in Lebanon where a buddy of mine worked. We ended up brazing in a replacement plug and flushing the system twice to get all the gunk out. The whole mess cost me 8 hours and $350 in towing and parts. Has anyone else dealt with freeze plugs letting go in older trucks during a quick cold snap?

I finally fixed a 6BT Cummins injector knock after months of headaches

Working on a 1995 Dodge 2500 near Denver last month, had a #4 injector that sounded like a hammer on idle. Swapped injectors, checked timing, even pulled the valve cover to look at pushrods. Turned out the copper washer on the injector was the wrong thickness by like 0.5mm. Anyone else run into a simple fix that took forever to find?

Swapped from a standard 10-micron fuel filter to a 2-micron on a 6.7 Powerstroke

The injector knock was gone in about 50 miles of driving, just from that cleaner fuel flow. I pulled the old filter after a week and the media was way darker than I expected. Anyone else seen such a quick fix from just stepping down the filter size?

My kid asked me why I still work on 'dirty' engines and it stuck with me

He's 12, and we were watching a show about electric cars. He just turned and asked, 'Dad, why do you fix the old smoky ones when the new ones don't need you?' I've been a diesel tech for 18 years, and that simple question hit hard. It's not about the smoke, it's about keeping the trucks that move everything running. Made me realize I need to explain the trade better. How do you guys talk to your family about what we actually do?

Had a weird injector cup failure on a 7.3 Powerstroke last Thursday

It was on a 2001 F-250 that came in running rough and pushing coolant out. Found the number 3 cup had a hairline crack right at the base, which is a spot I don't see fail often. Ended up pulling the head to do it right and avoid any sealant getting into the oil galleries. Anyone else run into a crack in that exact spot, or was this just a one-off fluke?