← Coolant loss on all engines
Symptoms · 5.9 Cummins (1994-2007)
5.9 Cummins (1994-2007): 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.
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.
verified
How widespread: Common
How it shows up
- coolant loss with no external leak traces; crusty white/green residue high on the block, under the intake side near the injection pump
Its other signs
- in cold climates the crack weeps and can dump coolant fast
How to tell it apart
- locate the '53' casting number on the block side (engraved, ~2 cm) and inspect the pump-boss area for weeping/crusting
- pressure-test the cooling system cold and re-inspect the boss area
- if buying a used 1999-2002 engine, check the casting number FIRST
Usual fix
replace the engine: used non-53 block or a reman long block (the crack itself is not weldable reliably)
Root cause, parts and sources →
verified
How widespread: Common
How it shows up
- coolant push-out under boost (degas overflow), combustion bubbles in the degas bottle
Its other signs
- cleaning up on stock tunes returns - the tell that it is boost, not the cooling system
How to tell it apart
- combustion-leak test at the degas neck + boost-event logging (overboost spikes)
- inspect for previous 'repair by re-torque' marks on the head bolts
Usual fix
head gasket set with ARP head studs (the community-standard upgrade), machined deck check
Root cause, parts and sources →
Other symptoms on the 5.9 Cummins (1994-2007)
Hard start, long crank or no-startLoss of power, limp mode or derateWhite smoke from the exhaustTicking, knocking, rattle or whineMisfire, rough idle, hesitation or surging
Everything on the 5.9 Cummins (1994-2007)Its recalls and bulletins