Ford Explorer: Rear main seal oil leak — a small part behind an expensive job

A rear main seal leak on the 2.3 is among the commonly reported faults on this Explorer. The seal itself is a cheap component; what makes this matter is where it sits. The rear main seal is at the back of the engine, between it and the gearbox, so reaching it means removing the transmission — commonly eight hours or more of labour on this vehicle, and more again on all-wheel drive. That turns a small part into a four-figure bill, and it is the reason a seller may know about a slow drip and simply keep topping up. The leak develops gradually, so a fresh oil change and a quick clean underneath can make a car look dry on the day. Look at where it lives rather than at the ground.

• Oil drips or spots where the car has been parked, under the middle of the vehicle
• Oil level dropping between services with no visible leak up top
• Oily film or grime on the underside around the gearbox bellhousing
• Burning oil smell after a longer drive
• Oil residue thrown along the underside towards the rear

Look at the ground first, where the car normally sits rather than where it is parked for the viewing — oil spots under the middle of the vehicle rather than the front are the pattern here. Then look underneath from the side without getting under the car: you are checking whether the area where the engine meets the gearbox looks dry and dusty, or wet and grimy with dirt stuck to an oily film. Compare it with the rest of the underside; a single dirty patch in that one area is the sign. Be suspicious of an underside that has recently been cleaned or sprayed, since that is how this gets hidden. Check the oil level and colour and ask how often it needs topping up. After the test drive, with the engine hot, check for any burning oil smell. Ask the seller directly whether the car has ever leaked oil and whether any seal work has been done. If a workshop inspection is possible: this is one worth having looked at on a hoist, because the diagnosis is easy from below and the bill is not.

$1,400 to $4,000 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.

• “Are there oil spots where the car is normally parked?”
• “How often does the oil need topping up between services?”
• “Has the rear main seal or any engine seal ever been replaced?”

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.