My wife's 2014 RAV4 petrol AWD is leaking petrol...

While it’s much less common to see a leaking rear main seal these days, it’s certainly not unheard of and definitely not an impossibility. While ever cars have seals and gaskets, they can fail, even if it’s not a common occurrence.

The rear main oil seal is the one located at the rear of the engine and is designed to allow the crankshaft to spin inside the engine without leaking oil through the rear main bearing to the outside world. When this seal wears or becomes hard with age and heat cycles, oil can get past it and that’s when you’ll start to find oily patches on the driveway under the car.

This seal is sandwiched between the engine and gearbox, so it’s quite a bit of work to separate those two components to gain access to the seal and replace it. It can easily be one of those $5 parts that costs $1500 to replace.

But before you commit to this, you need to make absolutely sure the rear main seal is the culprit. The best way to do that is to thoroughly clean the engine to remove any oil and then take it for a drive where it gets fully up to temperature. From there, you should be able to see where the oil is coming from and whether that place is the rear main seal. It might take a couple of journeys before the oil leak starts to show up again.

Don’t be surprised if the leak actually turns out to be from some external plumbing or even a seal or gasket at the back of the engine near the top, where the oil is escaping, running down the back of the engine and appearing to come from the rear main seal. Oil leaks can be tricky little devils, so take the time to diagnose the source carefully or you may find you’re replacing a seal that is perfectly fine. At which point you’ll have spent your money and still have an oil leak.