EGR Cooler Replacement — Duramax, Cummins & Power Stroke
How to replace a failed EGR cooler on a diesel truck. Covers symptoms of failure, coolant contamination diagnosis, and complete replacement procedure.
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Instructions
Diagnose EGR Cooler Failure
Symptoms: white smoke from the exhaust (coolant burning), sweet smell from exhaust, coolant loss with no visible external leak, milky residue in the coolant reservoir, overheating. Diagnosis: Remove the EGR valve and look for coolant residue or white deposits. Pull the intake manifold and look for coolant pooling. A combustion leak test (block tester) on the coolant reservoir detects combustion gases in the coolant, confirming a failed EGR cooler. The LB7/LLY Duramax and early 6.7 Power Stroke are notorious for EGR cooler failures.
Drain Coolant & Flush the System
Before any disassembly: drain the entire cooling system. If coolant is contaminated with exhaust gas or oil, flush the system thoroughly with distilled water before refilling with new coolant. Exhaust gases in the coolant raise pH and destroy aluminum components. Use a cooling system flush product and flush until the discharge runs clear.
Remove Intake Manifold & EGR Components
The EGR cooler is typically located between the exhaust manifold and the intake manifold. Removal requires: removing the air intake system, disconnecting EGR valve electrical connector, removing the EGR valve bolts, removing the intake manifold (may require removing the fuel rail and injectors on some engines), disconnecting EGR cooler coolant lines (clamp and slide off). Label all electrical connectors and coolant hoses with tape as you remove them.
Remove the EGR Cooler
Unbolt the EGR cooler from the exhaust manifold and from the intake side. The cooler is typically 4–8 bolts on each end. Have rags ready — residual coolant will drain. Inspect the exhaust manifold gasket surface and intake manifold gasket surface — replace any damaged gaskets. Clean all mating surfaces with a gasket scraper.
Install the New EGR Cooler
Use all new gaskets — never reuse old EGR cooler gaskets. Apply a thin coat of high-temp RTV to any surfaces specified by the manufacturer. Bolt up the new cooler to the exhaust manifold first, then the intake side. Torque all bolts to spec (typically 18–22 ft-lbs for EGR cooler bolts). Reconnect coolant lines — replace hose clamps with new ones. Reinstall the intake manifold with new gaskets, torquing in the specified sequence.
Refill Coolant & Bleed the System
Refill with the correct coolant spec for your engine. Bleed air from the cooling system: locate the bleeder valve (usually on the thermostat housing) and open it while filling. On engines without a bleeder, squeeze the upper radiator hose while filling to burp air out. Run the engine to operating temp with the heater on full heat to purge air from the heater core. Watch for bubbles in the coolant reservoir — bubbling after the engine is hot indicates remaining air or a combustion gas leak. Top off coolant after the engine cools.
