Nissan Patrol & Landcruiser Overheating Problems

Time and time again, we’re contacted by customers who have overheating problems with their diesel engines that they just can’t rectify. Many have spent $3,000 to $4,000 on big-core radiators, new water pumps, thermostats, fan hubs, chemical cleaning and more — yet still haven’t fixed the problem.

Short answer: if your diesel runs hot under load but cools down when you back off — and new radiators, pumps and thermostats haven’t fixed it — the real culprit is often dirty engine oil and sludge, not the cooling system. Clean oil is essential for carrying heat away. Get the basics right before spending big.

The typical pattern is that their engines run hot under load (towing a trailer, climbing a range, higher cruising speeds) rather than when idling in traffic. As soon as they back off the load, the temperature drops. It’s particularly a problem with 4×4 and light-vehicle diesels.

It seems that very few people — even some running radiator shops — realise that the engine oil has a crucial role to play in the cooling system. Engine oil actually has 5 duties to perform:

• Effective lubrication to minimise wear
• Keeping internal components clean
• Protection against corrosion
• Cooling
• Providing a fluid seal

A good strong supply of oil to all parts is crucial for effective cooling. It is particularly important to remove heat from around the pistons. Any deposits around the piston rings, top lands and skirts insulate against heat transfer. Engine oil sludge is a big problem: it can reduce oil flow by constricting oil galleries, reduce oil pump output, and insulate against heat transfer around internal oil coolers. Dirty, sooty oil doesn’t carry heat away — it absorbs heat but doesn’t disperse it as well as clean oil does.

As several hundred of our customers have found out over the years, you can spend some pretty big dollars trying to sort out overheating issues. Our advice is to make sure the basics are right before you start spending big on a trial-and-error basis.

Before you part with big dollars, check that:

• the lubricating system and crankcase are clean;
• the radiator and cooling system are sound and clean;
• the thermostat is working;
• the temperature gauge and sensor are working;
• the sensor wires and connections are sound.

If your vehicle was designed with a standard radiator, why should it need a big-core radiator to fix overheating? Surely it’s more likely to be something basic creating the problem.

Solutions to Your Overheating Problems

Our Flushing Oil Concentrate and Cleanpower pack has been solving these overheating problems in diesels for nearly three decades now.

By removing the unwanted sludge and built-up oil deposits, the Flushing Oil Concentrate restores a pristine level of cleanliness to all oil-wetted parts of the engine. When customers have tried everything else and failed, this is usually the answer. If only they’d come to us first and got the basics sorted, they’d have saved themselves big dollars.

For the full flushing method, see our guide on why you should flush a diesel engine (including the 6-step process).

For more information on how to stop overheating problems, give the team at Cost Effective Maintenance a call on 07 3376 6188.

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