Nissan Patrol: TD42 Thermostat Housing Crack and Coolant Loss

The TD42 uses a cast iron block with an aluminium thermostat housing. Thermal cycling over many years causes the dissimilar metals to fatigue at the gasket face, and the housing develops hairline cracks at the upper hose outlet and at the coolant temperature sender boss. Slow coolant loss from this area is frequently mistaken for a hose leak and left unaddressed. On turbo-equipped TD42T variants (fitted to some Y61 export models) the turbo coolant return line banjo bolt threads into the block and can strip or weep at the seating washer, compounding coolant loss.

• White mineral deposit or rust staining around the thermostat housing
• Coolant smell from engine bay after shutdown
• Slow coolant level drop over weeks without visible puddle on ground
• Temperature gauge fluctuating at operating temperature

With engine cold, clean the thermostat housing and surrounding area with a rag, then run the engine to operating temperature and inspect for weeping coolant at the housing-to-block joint, at the temperature sender boss, and at both hose outlets. On TD42T variants, check the turbo coolant supply and return banjo fittings for seepage. If a workshop inspection is possible: Pressure-test the cooling system to 100 kPa and hold for 10 minutes — any drop indicates a leak path.

Parts involved: Thermostat.

$200 to $700 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 thermostat housing been replaced or resealed recently?”
• “Is there any history of overheating or coolant loss?”

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.