A limited service campaign for the 2004-2007 Toyota Prius has been announced due to a possible water pump issue.

The water pump in question cools the hybrid system components, and not the internal combustion engine. A fault in the pump can cause the build-up of air bubbles, disrupting coolant flow. This can eventually lead to overheating.

Toyota is quick to point out that this is not a recall, but rather a limited service campaign, since there is no safety risk. As the components heat up, the check engine lights come on. If the temperature reaches dangerous levels, the Prius enters a “fail-safe mode” to allow it to limp home without any damage to the hybrid components.

Around 378,000 cars are affected by the campaign. Notifications will go out to owners in early December.

Press Release

Toyota Announces Limited Service Campaign of Certain 2004-2007 Prius Vehicles

Toyota Motor Corporation announced it will repair 378,000 Prius vehicles in the United States from model years 2004-2007 to correct a possible water-pump condition that could cause coolant to overheat resulting in reduced power output.

“The water pump is part of a system designed to cool the hybrid powertrain components and is separate from the engine cooling system,” said John Hanson, Toyota Motor Sales National Manager of Environmental, Quality and Safety Communications. “A fault in the water pump can cause air bubbles to build up and disrupt the flow of coolant, which can lead to overheating.”

The heating of the components could trigger the check engine light “on” condition. If the temperature of the hybrid components becomes too high, the vehicle will enter “fail-safe mode” to prevent hybrid component damage.

This customer support campaign is not a recall as Toyota has determined it is not a safety issue and the company has not received any reports of accidents or injuries related to this condition.

Owners of the involved vehicles will be notified by first class mail beginning in early December 2010. Toyota dealers will replace the water pump with a newly designed one at no charge to the vehicle owner as long as the owner arranges for service before Nov. 30, 2013. Owners who have previously paid for repairs to address this specific condition should refer to the owner letter for instructions regarding reimbursement.

Detailed information and answers to questions are available to customers at the Toyota Customer Experience Center at 1-888-270-9371.

Source: Toyota