D13/MP8 EGR Cooler Coolant Leak (Common High-Mileage Failure)
The VOLVO-MACK-MP8-EGR-COOLER-COOLANT-LEAK (Volvo/Mack D/MP Series) diesel fault code means: D13/MP8 EGR Cooler Coolant Leak (Common High-Mileage Failure). This is a serious severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- intermediate
- Estimated cost
- $1,800-$4,500
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Common Symptoms
- Gradual coolant loss between service intervals
- White steam from stack under load
- Sweet exhaust smell
- Engine derate from high coolant temp fault (MID128-PID110-FMI16)
- Heater works intermittently
- Pressure in cooling system rising unusually
Probable Causes (Ranked by Likelihood)
- Internal EGR cooler crack or tube erosion (very common on MP7/MP8 around 400K-700K miles) Very Likely
- EGR cooler external coolant fitting leak Possible
- EGR cooler gasket at cylinder head failed Possible
- Cracked cylinder head masquerading as EGR cooler leak (rule out with isolation test) Possible
- Failed water pump or thermostat contributing to coolant loss Less Likely
Frequently Asked Questions
What does Volvo/Mack code MP8-EGR-COOLER-COOLANT-LEAK mean?
Volvo/Mack code MP8-EGR-COOLER-COOLANT-LEAK (D13/MP8 EGR Cooler Coolant Leak (Common High-Mileage Failure)) is a serious-severity diagnostic trouble code set on D11/MP7, D13/MP8, and D16/MP10 diesel engines in Volvo VNL/VNR and Mack Anthem/Pinnacle/Granite/Titan trucks. It indicates a fault in the EGR cooler system and should be read with Volvo Premium Tech Tool (PTT) or Mack Guided Diagnostics.
Can I drive a Volvo or Mack truck with code MP8-EGR-COOLER-COOLANT-LEAK?
Short distances may be acceptable to reach a repair facility, but the fault will escalate to derate (typically 55 mph then 5 mph on aftertreatment faults). Do not defer diagnosis beyond a shift.
How much does it cost to fix Volvo/Mack code MP8-EGR-COOLER-COOLANT-LEAK?
Typical repair falls in the range $1,800-$4,500. Sensor/wiring repairs are at the low end; EGR cooler, NOx sensor set, DEF pump, injector, or head work runs at the high end. Volvo PTT or Mack Guided Diagnostics is normally required for calibration and parameter programming.
What actually makes the computer set this EGR code?
California's heavy-duty OBD regulation sets the low-flow trip point where a decrease from the manufacturer's specified EGR rate would push NMHC, CO or NOx past 2.0 times the applicable standards, or PM past the standard plus 0.02 g/bhp-hr (Title 13 CCR 1971.1, section (e)(3.2.1)). Note the second route: it must also flag the case where the EGR system has hit its control limits and simply cannot reach the commanded flow — so this code can set with the valve working and the system still unable to deliver. This threshold comes from the heavy-duty OBD regulation, which covers 2010 and later heavy-duty engines. If your engine is in a pickup at or under 14,000 lb GVWR it is certified under the separate medium-duty rule instead, so treat this as the design intent rather than your engine's exact limit.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
Pressure-test the cooling system and monitor for leak-down.
Isolate EGR cooler by clamping inlet and outlet coolant hoses; re-pressurize and observe.
If pressure drop stops during isolation, EGR cooler is confirmed leaking.
Verify no combustion-gas in coolant (block-test) before blaming the EGR cooler.
Replace EGR cooler with new unit, new gaskets, and new coolant; inspect head surface for erosion at the mounting face.
Pressure-test the new cooler and refill cooling system; verify fault clears with Volvo PTT or Mack Guided Diagnostics.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- California Code of Regulations, Title 13 section 1971.1 (Heavy-Duty OBD)malfunction criteria, section (e)
Commonly Affected Vehicles
- Volvo VNL 760/860 with D13
- Volvo VNR 640 with D13
- Mack Anthem with MP8
- Mack Pinnacle with MP8
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