M9R engine reliability: strengths, watch-outs, and known issues

Bosch piezo injectors are demanding on diesel quality and have poor repairability, but the main issues are caused by unreliable fuel pressure regulators. Diagnosis of poor starting or floating idle should start with them.

This engine was developed jointly with Nissan engineers, so the timing drive is chain-based. Opinions on its lifespan vary greatly: some claim 400,000 km on the original chain, while others needed replacement at 150,000 km.

All versions of these diesel engines are equipped with reliable Garrett turbochargers, but boost errors appear regularly. Usually the vacuum system, boost sensor, or sticking variable geometry mechanism is at fault.

The throttle assembly is complex, with electronic actuation and an integrated EGR valve. This design is sensitive to contamination and tends to jam at the worst moment.

The classic problem for all modern Renault diesels of bearing cap rotation has not spared this engine, but it is less pronounced than on other company engines.

Also, the oil separator is relatively weak, injectors stick to the cylinder head, the crankshaft pulley damper often fails, and the diesel particulate filter clogs quickly.