The Lexus GX460 and the 4.6 liter 1UR-FE engine can, as it ages, develop a coolant leak from the valley of the engine. This can cause pooling of coolant in the engine valley, often running down the back of the engine between the flex plate and transmission, or down the transmission itself. Diagnosing the cause of the leak is tricky because it originates deep in the valley of the engine.
Underneath the GX460’s intake manifold, Lexus engineered a cover plate that houses a coolant galley to pass coolant between the cylinder heads and heater core. With the intake manifold and a great deal of secondary air injection tubes removed, you’re looking at something like this:
Valley plate leaking coolant
The circled areas indicate coolant leaking from the valley plate that covers this coolant galley. With the plate removed the leaks are a bit more obvious. In the photo below the plate’s perimeter is indicated by the red line:
Valley plate removed
And the leaks more closely:
Coolant leaks up close
The valley plate is sealed with Toyota’s special 1282B fix-in plate gasket specifically designed for Toyota cooling systems. It works incredibly well when applied properly. With the plate cleaned of residual gasket and resealed with fresh 1282B, the problem should not reoccur.
The above cooling system repair is something, as a Toyota and Lexus specialist, CARspec is equipped to handle. As Minneapolis, Minnesota’s premier independent Toyota and Lexus specialist we see this and other GX460 specific issues regularly and are well equipped to handle all manner of issues. If you think you have a coolant leak from your GX460, don’t hesitate to give us a call and schedule a no-charge inspection at (952)426-4798 today!
