c/diesel-mechanics

Two-Stroke vs Four-Stroke Detergents: I was wrong about one of them

For years I swore by four-stroke oil additives for cleaning injectors on highway trucks. Thought two-stroke oil was just a small engine thing. Then I ran a bad tank of fuel through my Peterbilt outside of Phoenix and the injector stuck open. A buddy told me to run a 2 ounce per gallon mix of cheap two-stroke oil in the next fill. I laughed at him. After 200 miles of hard interstate driving, the truck smoothed out and the smoke cleared up. Now I keep a jug of it in the shop but I still question the long term effects on DPF systems. Anyone else use this trick or have a story where the opposite happened, where a trusted additive failed you completely?

Running a compression test taught me more than any spec sheet ever did

Last month I had a 2008 Freightliner with a miss that was driving me nuts, so I finally pulled the valve covers and did a proper compression test instead of guessing. The readings came back at 310, 305, 290, 180 on cylinders 3, 6, 8, and 9, which totally changed how I looked at the whole engine. I found out from a old manual at the shop that these Detroit 60 series should stay within 15% of each other, and that 180 was way outside the limit, so it saved me from rebuilding the whole thing when it was really just a cracked piston head. The numbers told me exactly where to start tearing down, no smoke and mirrors needed. Has anyone else had a compression test reveal something that contradicted what the computer was saying?

Discovered a trick for freeing stuck glow plugs without snapping them

I had a 7.3 Powerstroke come in last week with two stuck glow plugs. Normally I'd soak them in PB Blaster and pray, but one of the old guys at my shop in Des Moines told me to heat the block around the plug with a heat gun for about 10 minutes before trying. Worked like a charm on both. No snapped tips, no helicoil needed. Has anyone else tried this method, or do you have a better approach for stuck plugs?

Just realized my $300 injector puller was a total waste

I bought a fancy injector puller set last year for doing powerstroke injectors. Figured it would save me time and hassle on the job. First few times it worked okay but then I had a stuck injector on a 6.0 last month and that puller just bent right up. Cost me $300 and I had to go back to the old slide hammer method I've been using for years. A buddy down at the shop uses a cheap $50 puller from NAPA and swears by it. Now I'm wondering if I just got a bad brand or if these expensive sets are mostly marketing hype. Any of you guys had luck with a specific puller that won't break the bank?

I still think glow plugs are overrated on older Cummins engines...

Had a guy tell me last week I was crazy for not replacing all six on my '96 12 valve. I've run that truck for 8 years now and only swapped two of them. Fires up fine down to about 20 degrees with a good battery and a little ether. Maybe I'm just lucky but I feel like people replace them in sets way too often. Anyone else stick with the originals longer than you're supposed to?

Old timer at the parts counter said I was wasting money on synthetic oil for my 7.3

Guy named Jerry at the NAPA in Bakersfield told me I was throwing cash away running synthetic in my 7.3 Powerstroke. Said these old IDI engines were designed for conventional 15w40 and the seals would start leaking. I argued with him for like 10 minutes but he just shrugged. 6 months later my rear main seal is seeping oil on my driveway. Should have just listened to the guy. Anyone else had seals go funny after switching to synthetic?

Why does nobody talk about injector return line leaks causing hard starts

Swapped out a whole set of injectors on a 7.3 Powerstroke two months ago and it still cranked forever when cold. Finally found the return lines were weeping air into the fuel... put new caps and o-rings on and it fires right up now. Anyone else run into this after replacing injectors?

Changed my mind about fuel filters after a shop foreman yelled at me

I used to just swap fuel filters whenever I got around to it, maybe every 30k miles or so. But this old foreman at a shop in Phoenix caught me and said 'you're just asking for injector failure at 100k doing that.' He showed me a cut-open filter from a truck at 15k and it was full of black gunk I never even thought about. Now I do them every 10k without fail on every engine I touch. Has anyone else had a filter look way worse than expected way early?

That fuel injector puller cost me 4 hours of my Saturday

Last month I was swapping injectors on a 6.7 Cummins and one of them was seized solid. I tried the usual tricks like soaking it in penetrating oil and tapping it with a hammer, but nothing worked for 2 hours. Ended up pulling the whole valve cover and using a slide hammer attachment I borrowed from a buddy, which finally got it out in 20 minutes. Anybody else got a go-to trick for stuck injectors that saves them time?

Old timer at the shop told me I was spinning my injectors wrong

Guy named Chuck with 40 years experience watched me torque down an injector in a 5.9 Cummins and just shook his head. He said I was overtorquing the hold-down bolts and that I should be using a 3/8 drive instead of 1/2 for better feel. I switched to a torque wrench that goes 10-150 ft-lbs and havent had a leaky injector come back since. Anyone else get a simple tip from a veteran that totally changed their install game?

Always used brake cleaner on injector O-rings until I had one swell up and lock in the bore

Pulled a set of 6.0 injectors a few years back and one of the new O-rings grabbed so bad I had to hammer the injector out. Reworked it and got a new seal kit. Buddy told me that brake cleaner swells viton O-rings like crazy. Switched to just lubing with diesel oil before install and haven't had one stick since. Anyone else run into this?

Pro tip: Don't buy those cheap fuel injector cleaning kits off Amazon

I wasted $45 on one of those in-line cleaning kits last month and it did nothing but clog my filter on a '06 Cummins, has anyone else had better luck with a specific brand or method?

Just passed 500 engine rebuilds and it hit me different

I was cleaning up after number 500 on a 6.7 Powerstroke last Thursday. Did the math on my old logbook and realized that's over 15 years of cranking bolts and chasing oil leaks. My back hurts all the time now (no surprise there) and my knuckles look like hamburger. But seeing that number made me feel something I wasn't expecting. Anyone else ever stop and count up how many motors they've actually cracked open?

Walked into a shop in El Paso that changed my whole view on injector cleaning

I was in El Paso last month visiting my cousin and he dragged me to this little diesel shop called Rojas Diesel Repair. I figured it would be some back alley operation, you know? But the owner let me watch him clean injectors using some ultrasonic setup (not the cheap ones you see on Amazon either). He showed me the before and after on a Cummins injector and I swear the improvement on spray pattern was night and day. I always thought those ultrasonic cleaners were just a gimmick for home use, but seeing it done right in a real shop with the right solution and cycle times totally flipped my opinion. Has anyone else seen a pro setup like that change your mind on something you thought was BS?

Tried a el cheapo injector puller vs a Snap-On one last Tuesday, what a difference

I had this old 5.9 Cummins that had a injector stuck good. I figured I'd save some cash and grabbed a $30 puller off Amazon. Big mistake. That thing bent like a wet noodle after two hits with the slide hammer. I ended up borrowing my buddy's Snap-On puller and it popped that injector out in like 3 seconds flat. The cheap one just couldn't get the grip right and flexed all over. The Snap-On had a better jaw design that clamped tighter and didn't slip. Cost me an extra hour of messing around though. Has anyone else run into a tool that just falls apart when you need it most?

Vent: Older mechanic told me I was overtorquing head bolts and I blew a gasket

I was doing a rebuild on a 5.9 Cummins last month and a retired guy came by the shop and told me I was cranking those bolts way too tight with a cheater bar, said I was gonna warp the deck. He was right, that engine developed a coolant leak after 50 miles and I had to pull the head back off and replace the gasket. Has anyone else had to eat crow on a torque spec they thought they knew?

Shoutout to the old-timer who showed me how to clean a injector cup properly

I was working on a 12-valve Cummins swap at a shop outside Portland about a month ago. This guy named Jerry, must have been 70 years old, walked over and watched me struggle with a stuck injector for 10 minutes. He didn't say a word, just pulled out a worn-down flathead screwdriver and tapped the cup a certain way that broke it free. Then he said "you gotta work with the metal, not against it." Has anyone else had a random older mechanic drop some simple tip that saved you hours?

Finally got a full 800 hours out of a set of injectors

Swapped a set of Bosch injectors into my old Freightliner last year and they just crossed 800 hours with zero issues - used to replace them every 400-500. What's the best luck you've had with a specific brand on high-mileage engines?

Spent $900 on a Snap-on scan tool and it either saved my butt or cost me big time

I dropped just under 900 bucks on a used Snap-on scanner last year for my shop. It diagnosed a ghost issue on a 2018 Freightliner that was stalling at random. saved me maybe two days of guessing. But a week later I tried using it on a 2020 International and it just gave me a code that was wrong. I got led down a rabbit hole and wasted a full afternoon replacing parts that didn't need it. So now I wonder if spending that much was worth it or if I should have just gotten a cheaper generic tool. Has anyone else had a high end tool burn them on a newer model?

Heard a shop foreman say he never uses torque wrenches on head bolts

Guy at the local diesel shop told me he's been wrenching for 20 years and just tightens head bolts by feel. I've always followed the spec - I snapped a bolt on a 6.7 Powerstroke last year doing it by feel. Is he full of it or am I overthinking this?

Tried that new DEF delete controller on my F250 and got a nasty surprise

I put one of those aftermarket delete controllers on my 2016 F250 last weekend, and after about 50 miles the truck went into limp mode and threw a P2002 code... Started smelling something burning too. Has anyone else had these things fry their DPF differential pressure sensor?

Had a piston ring land crack on a Series 60 last Tuesday

Was doing a routine overhead on an '02 Freightliner and found the #4 ring land split clean in two. Anyone else seen these late model Series 60s start doing this more often?

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