Pajero Engine Oil Cooler 1240A001

The NS NT NW NX 4M41 Engine Oil Cooler comes as an 'assembly' which includes the 'Cooler core' and 'Outer housing' which comes pre-assembled from the factory with internal core flange gaskets in-place fitted and torqued in Factory. This is Genuine Mitsubishi Part Number 1240A001 

 

4M41 Engine Pajero Engine Oil Cooler  - Known Issues

There are Many reports of  the Pajero 4M41 Engine Oil Cooler (Not to be misinterpreted or confused with the transmission oil cooler) Leaking suddenly and forcing the engine oil into the radiator and coolant lines which results in the coolant Reservoir Filling up and overflowing Black brown sludge substance out of the coolant reservoir and onto the ground, near the front / passenger side of the vehicle.

 

Usually when this happens, The cooler core has cracked, burst or a small rupture has formed in the core that expands and opens under pressure. When inspecting a leaking core, it may require a pressure test to show or produce the leak.

 

This issue has proven very common in the NW range, but not limited to,  as there are reports of Nx and other models suffering the same issue.

 

Once a cooler core has leaked or ruptured filling the cooling system with oil , several initial flushes with a special solution (water soluble degreasing agent) (Penrite Australia make a specific product 'Oil in Radiator remover")  will be required, and further flushes down the track, as any oil contamination of the rubber hoses and cooling system seals will short life greatly afterwards.

 

There is no accurate detail on what milage the oil cooler issue happens, or the true cause, However it seems more common in the 160 to 200k range, in addition there are reports of failings as early as 100k and other reports of 400k plus and never had a oil cooler fail ever. 

Whether it be a bad batch?, or internal coolant corrosion of the cooler core walls ? or heat up and cool down - expansion / contraction cycles of the core metal causing long term metal fatigue?...Who knows

 

This issue can be Wrongly diagnosed, easily, due to the symptoms, similar to a blown Head Gasket if a mechanic is not aware of the common issue, and has not taken the time to thoroughly inspect or run any tests, leaving the client with costly repairs replacing the wrong parts.

 

Many NW and NX owners are Replacing the Engine Oil cooler as a maintenance item now, Before it fails, due to the known issue. Which is a smart idea and saves, reduces,  later costs , breakdowns, and additional constant coolant flushing and hose replacements, Not to mention the risk of major engine damage if driven undiagnosed or driving off without seeing symptoms (puddle of black oily substance under front passenger side of vehicle).

  

 

Disclaimer: Any Information listed is provided as general nature information only, We provide no warranty or guarantee for any information provided .  You should seek professional advice and guidance from your Automotive technician or mechanical workshop based on your  particular circumstances with your particular Vehicle.

​

​

​