Engine Damage through Water Ingestion
with Factory Bull Bar Fitted
The standard air intake arrangement on the 120 Series draws air from inside the front RHS cavity created by the exterior panel and inner guard as shown below.
There is also a plastic wheel well liner that prevents water and other "stuff" from being thrown up by the wheel into the cavity and air intake. When the factory bull bar is fitted, the front portion of the wheel well liner is cut and trimmed away. This is necessary due to the fact that the bull bar is mounted to the chassis and the liner to the body. The body and chassis move independently to each other and direct attachment to both will cause failure of the liner. By trimming way this part of the liner, the forward splash guard is effectively removed.
The picture below is a worm's eye view looking up the RHS of a 120 Series GXL fitted with a factory bull bar.
The picture clearly shows the trimmed wheel well liner (inner guard) and you can just peek at the forward edge of the air intake inside the guard cavity. In standard form the liner continues forward and attaches to the bumper bar, creating an effective shield against water being splashed up from the front wheel.
When the front portion of the liner is cut away, the air intake becomes exposed to water being splashed up from the front wheel. Normally in suburban road use this may not cause a problem, however when the water depth increases, the wheel pushes a wave of water forward and it is deflected up into the air intake cavity - and free to be drawn into the engine through the air intake. After some rough calculations, in situations where the water level is above 100 mm and vehicle speed above 30 kph, sufficient water volume may be pushed up to cause engine damage.
The reports of engine failure (some well documented in the 4WD press) all relate to the petrol engine. There is good reason for this as the air intake system is completely different to that of the 1KZ-TE turbo diesel - it is also more exposed.
In the case of the diesel air intake, a long (though restrictive) air duct is situated inside the guard cavity - and faces towards the rear of the car. This duct passes air directly into the pre-spinner assembly.
In the case of the 4.0L V6 petrol engine, a much higher flowing air intake is required due to the high air demands of this engine (24.1 lb/min of air versus 17.9 lb/min for the turbo diesel). The picture below shows the pre spinner assembly and the rubber air entry boot attached. The rubber air entry boot is situated inside the guard cavity.
Front view of pre spinner with rubber boot removed
The picture above shows the rubber air entry boot in more detail. When installed on the vehicle, the open scoop sits at around 40 deg from the horizontal facing towards the rear of the vehicle.
Now, let's cast our minds back to the worm's eye view shown again below.
Water that is pushed up by the front wheel is placed pretty much at the same position that the air intake of the 4.0L V6 engine is situated. And, being an open scoop, there is a good chance that the water will be drawn into the engine.
The diesel intake on the other hand as seen previously has an air intake that is positioned a good deal further back from the front of the car. Consequently, a smaller volume of water reaches the air intake, thus lessening the chance of water ingestion.
Unlike other Land Cruisers such as the 80 and 100 Series, the air filter assembly on the petrol 120 Series does not contain any guards or cyclonic action to prevent water from being drawn into the air filter. Neither does the diesel model air intake, however visually, it is more suitable to deal with water.
Whilst the diesel engine air intake is more protected, it is not uncommon to see a wet air filter after modest water crossings well under the specified wading depth. This indicates that water has entered the air intake system but not in sufficient quantity to cause engine damage.
The pre spinner above off a diesel 120 shows clear evidence of muddy water entering the air intake system.
Of the handful of engine failures we are aware of, these have been assessed on an individual basis by Toyota dealers with regard to repairs carried out under warranty. To date though we are not aware of any that have been covered by warranty though it is common for the consumer and Toyota to reach an agreement that is kept private. If indeed the owner had been notified that fitting a factory bull bar would reduce the wading depth from 700mm to 100 mm, then it is entirely reasonable that warranty be refused. However, we are not aware of any such warning or change in specifications. That said, owners of vehicles fitted with the factory bull bar do need to contact their dealers so that a thorough inspection be carried out to ensure that the specified wading depth is either maintained or reduced to a level that will ensure no engine damage occurs - or modifications performed to ensure that water is not pushed up into the air intake. To date, we are not aware of any easy modification to rectify the situation.
Note that the Toyota bull bar only has been inspected. Other bull bars may have splash guards or be designed such that the air intake is protected from water ingress. In future, we will endeavour to update this page with more examples.
As indicated previously, due to the fact that the plastic liner is mounted to the body, it is not feasible to mount the leading edge to the bull bar, as it is mounted to the chassis and the two move independently to each other. The plastic liner is also flimsy and can be pushed back by air pressure when traveling at speed, or by water during a river crossing for example. The animated picture below shows the level of deformation using light hand pressure on the plastic liner. This is enough to have the liner make contact with the tyre.
The picture below is another worm's eye view showing a plastic liner on the LHS that has been ground down from making contact with the rotating wheel at highway speed. In this case, a rubber support was fabricated to pull the liner forward and to limit the amount of movement and avoid contact with the tyre.
There are a number of different methods to keep the liner in place and off the front wheel. It is not uncommon for zip ties to be used however given the fragile nature of the plastic liner, only time will tell if this is successful.