Mitsubishi Pajero: NM/NP 4M41 Intercooler Pipe Split at Boost Clamp

The NM and NP generation 3.2 DI-D 4M41 engine uses rubber intercooler hoses connecting the turbocharger outlet to the intercooler and from the intercooler to the inlet manifold. The factory spring clamps and later aftermarket worm-drive clamps allow the rubber hoses to crack or split at the clamp edge under sustained boost pressure, particularly at the lower intercooler outlet pipe and at the top-pipe connection to the inlet manifold. When a pipe splits or blows off, the vehicle enters limp-home mode as the ECU detects loss of boost, or the engine loses power dramatically without triggering a fault code if the split is partial. Symptoms are most apparent under hard acceleration. The hoses become brittle with age and heat cycling; vehicles over 15 years old should have all intercooler pipework inspected as a routine item. Repair with quality silicone hose and T-bolt clamps is the preferred permanent fix.

• Sudden significant loss of power under acceleration, returning at light throttle
• Black smoke from exhaust under load after sudden power loss
• Boost gauge dropping to zero under acceleration if fitted
• Hissing or fluttering sound from engine bay under boost
• Limp-home mode activation with turbo-related fault codes

With engine cold, squeeze and inspect all intercooler hoses for cracks, hardening, or splits particularly at each clamp location. Pay special attention to the bottom intercooler pipe and the upper connection to the inlet manifold. Look for black soot tracking from any pipe joint indicating a boost leak. With engine warm, have a helper hold the engine at 2000 rpm in neutral while you listen for any hiss or flutter from the intercooler circuit.

Parts involved: Intake manifold, Turbocharger.

$120 to $480 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Has the vehicle ever suddenly lost power under hard acceleration?”
• “Have the intercooler hoses been replaced and with what type of clamp?”
• “Has the turbo boost ever dropped unexpectedly?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.