We see our share of leaking water pumps – it is one of the most common points of failure across Toyota, Lexus, and Scion models. In response to this, Toyota issued a technical bulletin to explain why a pump may need replacement, what a leak looks like, and when coolant residue may be normal. That bulletin is linked here.
CARspec recommends replacement if:
The coolant reservoir is below the lower limit OR
The water pump bearing makes excessive noise or has excessive free play OR
There is enough wet coolant on the water pump to mark a paper towel OR
Dried coolant deposits cover a large area of the water pump and surrounding engine area
In the above example from Toyota, further inspection is required. In figure 1 and 2, if the deposits are damp when pressed with a paper towel replacement would be required. In figure 3, CARspec would inspect for wet coolant, likely find none, clean the deposits and advise the guest to monitor the coolant level and temperature.
The majority of leaks from the water pump are temporary and require only a cleaning, a bit of coolant and some monitoring.
We here at CARspec hope this clears up some questions a guest may have about water pump replacement.