← Coolant loss on all engines

Symptoms · Duramax LML (2011-2016)

Duramax LML (2011-2016): losing coolant

2 documented failures on this engine list this among their signs. They are ordered from the most widespread down. Each one shows the signs in its record's own words, how to tell it from the others, the usual fix and any recall or bulletin.

1. Cooling system wear: water pump, fan clutch, oil cooler (LML) Occasional
2. EGR valve / cooler carbon and coolant service (LML) Occasional

Not sure which engine you have, or want the recalls for your exact truck? Check your VIN: it names the engine and lists the campaigns for that model year. Whether a recall is still open on your VIN: nhtsa.gov/recalls.

1 Cooling system wear: water pump, fan clutch, oil cooler (LML)

aggregated How widespread: Occasional

How it shows up

• coolant seepage at the water pump weep hole; bearing growl

Its other signs

• overheating under tow traced to a locked/loose fan clutch
• oil-cooler service themes carried over from the earlier Duramax era

How to tell it apart

• pressure-test the system; verify thermostat and fan clutch operation under load before radiator replacement
• inspect the oil-cooler lines at service intervals

Usual fix

replace the failed cooling component; use the correct coolant spec on refill

Root cause, parts and sources →

2 EGR valve / cooler carbon and coolant service (LML)

aggregated How widespread: Occasional

How it shows up

• coolant loss traceable to the EGR cooler; carbon buildup at the valve

Its other signs

• EGR flow codes, hesitation under load

How to tell it apart

• command the EGR valve with a bidirectional tool before replacing it
• pressure-test the cooling system to separate a cooler leak from other coolant loss

Usual fix

replace the EGR valve or cooler as testing dictates

Root cause, parts and sources →

Other symptoms on the Duramax LML (2011-2016)

Hard start, long crank or no-startLoss of power, limp mode or derateTicking, knocking, rattle or whineMisfire, rough idle, hesitation or surgingDEF, DPF and regeneration warnings

Everything on the Duramax LML (2011-2016)Its recalls and bulletins

Order: how widespread each failure is in its record (near-universal, very common, common, occasional, rare), then the number of NHTSA owner complaints that match its keywords. Complaint counts are keyword matches, not a manual review of each complaint. A symptom listed here means the failure is documented with that sign; it is not a diagnosis of your truck. Tiers: verified, aggregated, contested, data-gap. How we tier and source facts.