Used 6.7 Cummins 2007-2018: what to check before you buy

1Before you go

Run the VIN and ask for the paperwork on the campaigns below: a done recall or program is a solved problem, an open one is a free repair the seller has not had done.

• Run the VIN

  It confirms the engine and lists the campaigns for that model year. Whether a recall is still open on this VIN: nhtsa.gov/recalls.

• Safety recalls on this engine
  • 17V-562 · 2013-2017 · Engine and engine cooling
  • 15V-592 · 2016 · Engine and engine cooling
  • 14V-635 · 2011-2014 · Engine and engine cooling
  • 08V-641 · 2007-2008 · Engine and engine cooling
  • 07V-093 · 2007 · Equipment

2Cold start and idle

Ask the seller not to start or warm the engine before you arrive. Most of these only show on a cold engine; then let it idle and listen.

• Lift pump / fuel delivery weakness
  • long cranks, hesitation, power loss when the tank is low
  • FCA (fuel control actuator) ticking / rough idle when failing
• Exhaust manifold cracking
  • exhaust tick on cold start that fades (or doesn't) with heat
• Grid heater 'killer bolt' ingestion
  • hard cold starts / no grid-heater cycling when the heater itself has failed separately
• EGR cooler failure
  • white sweet-smelling smoke, coolant loss with no external leak
  • in bad cases: hydro-lock symptoms / white smoke clouds at startup
• Head gasket failure (tuned / overheated trucks)
  • white smoke, sweet smell; overheating events in history
  • misfire on startup after sitting (fluid into a cylinder)

3Scan for codes

A basic OBD-II reader shows stored and pending codes; on a diesel ask a shop for a full scan if you can. These are the codes our records tie to known failures on this engine.

What a code means on each engine: trouble codes by engine.

4Hood up and underneath

Engine off, in daylight, with a flashlight.

• DEF / SCR system failures (2013-2018)2013-2018
  • white crystalline urea deposits around the DEF tank, pump and injector

  To confirm: read DEF/SCR DTCs and current DEF quality / NOx PIDs before parts-cannoning

• Water pump failure
  • coolant weep from the weep hole / front cover area
  • coolant smell, occasional low-coolant warnings

  To confirm: trace the leak to the weep hole with a UV dye / clean-and-observe

• EGR cooler failure
  • EGR cooler DTCs / flow codes; coolant smell at the exhaust

  To confirm: block-test the coolant for combustion gas (careful: EGR cooler gas also shows)

5Test drive

At least 20 minutes, including a highway run and a hill or a load if you can.

• DPF clogging / regeneration problems
  • 'exhaust filter full / regeneration required' message on the overhead console
  • frequent or endless regenerations; aborted regens on short trips
  • loss of power (inducement / derate) until regeneration completes
  • excessive idle, white/grey smoke during regen, hot exhaust smell
  • fuel smell in the oil after repeated failed regens
• Holset VGT turbo sticking / actuator failure
  • low power / boost DTCs (over/underboost), smoky acceleration
  • excessive idle/lope or whistle change; failed regens because the turbo cannot build regen heat
• DEF / SCR system failures (2013-2018)2013-2018
  • DEF-system warning / 'service DEF system' message, then 5 mph derate if ignored
  • NOx sensor DTCs (P2200-family); 'DEF quality poor' messages
  • DEF pump / heater failure, especially after a freeze (pump assembly contains a heater)
  • failed emissions test / MIL with no driveability change
• Water pump failure
  • bearing noise from the front of the engine; overheating if run low
• Grid heater 'killer bolt' ingestion
  • sudden loss of power, knocking or clicking, then catastrophic engine damage once a broken nut or bolt reaches a cylinder (owners most often name cylinder #6)
• EGR valve sooting / failure
  • rough idle, smoke, occasional power loss; failed regens
• Injector 'chuffing' / seal blow-by
  • audible 'chuff chuff' exhaust beat (compressed gas past an injector's copper seal)
  • fuel smell, smoke, rough cylinder balance; balance-rate DTCs
• Fan clutch failure (overheat while towing)
  • temperature climbs only under load/towing/AC-high but stays normal unloaded
  • fan-clutch DTCs; belt noise from a wobbling clutch

6After the drive

Hot engine, parked: the dipstick and the coolant reservoir tell you what the drive did. Then shut it off and restart it hot: some failures only show on a hot restart.

• Injector 'chuffing' / seal blow-by
  • fuel in the oil / rising oil level (pairs with the oil-dilution mode)

  To confirm: cylinder-balance / contribution test to locate the weak hole

• EGR cooler failure
  • pressurised cooling system (bubbles at the degas bottle)

  To confirm: block-test the coolant for combustion gas (careful: EGR cooler gas also shows)

• Fuel dilution of engine oil (failed regens)
  • oil level RISING between services (fuel accumulating)

  To confirm: track oil level between changes - a rising level on a diesel is fuel or coolant, never good

• Head gasket failure (tuned / overheated trucks)
  • coolant loss, combustion gas in the cooling system, pressurised degas bottle

  To confirm: block-test the coolant for combustion gas

What it costs if you find it

Parts budgets from our repair recipes for this engine: Dave's Auto Center's prices where Dave's lists the part, approximate OEM and maker catalog prices (rounded) for the rest; labor not included. A campaign listed next to a failure may make the repair free on a covered truck: check it by VIN.