Silencing a Noisy Prius

s early as the mid-1600s, some forward-thinking people began envisioning steam-powered vehicles. In the 1800s, a great deal of time and energy was spent on developing electric propulsion. Around 1900, European carmakers began pairing gasoline engines with electric motors in a system we refer to today as a hybrid system. In the years since, electric and then steam-powered vehicles gave way to the gasoline engine as the primary source of propulsion.

Now, travel forward in time to the past! The Toyota Prius and other “revolutionary” hybrids are everywhere. And development continues on promising new power sources as well.

Automotive technology is advancing at a pace that was unthinkable just a few years ago. And propulsion is just one example. Electronic systems control every aspect of today’s vehicles. Navigation, collision avoidance, self-parking, safety systems … the list goes on and on. With vehicles becoming more and more complex, how do you determine the best and most cost-effective manner of repairing cars that are, in fact, computers with wheels? There is only one reliable answer: manufacturers’ repair information.

Whether the issue is electronic or mechanical, accessing OEM repair procedures, diagrams, specifications and technical service bulletins (TSBs) is the best strategy for performing safe, efficient and proper repairs. TSBs are an especially important tool for quickly diagnosing unusual issues. In many cases the problem concerning the car in your bay may already be known and a repair procedure may have been published by the factory.

Here is an example excerpted from a Toyota TSB concerning a knocking noise in some older Prius vehicles.

Prius Metallic Knock

Some Prius owners may complain of a metallic knock or clunk noise from the engine bay heard only while driving over speed bumps or rough road conditions. The engine mount assembly has been improved to prevent this condition.

Applicable Models

This TSB applies to vehicles produced BEFORE the Production Change Effective VINs shown.

Parts Information

NOTE: The affected mount is attached to the hybrid transaxle. The part name in this service bulletin is “Insulator, Engine Mounting, LH” (left-hand). This is also referred to as “No. 3 Engine Mounting Bracket.”

Required Tools & Equipment

Warranty Information

This repair is covered under the Toyota Powertrain Warranty. This warranty is in effect for 60 months or 60,000 miles, whichever occurs first, from the vehicle’s in-service date.

Repair Procedure

Review safety procedures in ALLDATA Repair S3000SM before beginning.

After verifying that the “knock” noise is coming from the area near the hybrid transaxle replace the engine mounting insulator LH with a NEW part.

1. Remove the inverter w/converter assembly following factory and/or industry standard approved practices.

NOTE: Do NOT replace the inverter.

2. Support the hybrid transaxle assembly by using a transmission jack.

3. Remove and replace the engine mounting insulator LH (No. 3 Engine Mounting Bracket)

(Figure 1).

A. Remove the engine mounting insulator sub-assembly LH from the vehicle.

B. Remove two nuts from engine mounting insulator sub-assembly LH

(Figure 2).

C. Replace the engine mounting insulator LH with the NEW part (P/N 12372-21111)

(Figure 3).

D. Tighten the 2 nuts. Torque: 47 ft lb (64 Nm, 640 kg cm)

E. Attach the engine mounting insulator sub-assembly LH on the vehicle. Torque: 59 ft lb (80 Nm, 800 kg cm)

4. Install the inverter w/converter assembly following factory and/or industry standard approved practices.

5. Road test to verify proper operation of the vehicle.

For more information on OE repair information, please visit www.alldata.com/promo/imp5tt/

NOTE: This Repair/Service Procedure is excerpted from a Technical Service Bulletin published by the vehicle manufacturer, and is intended for use by trained, professional technicians with the knowledge, tools and equipment to do the job properly and safely. It is recommended that this procedure not be performed by “do-it-yourselfers.”

Dennis Shortino has over 32 years of experience as an auto technician / shop manager and nine years as an auto instructor and contract trainer. Dennis has written for Check Chart’s college level auto repair text books and ASE study guides. He’s an ASE Master & Advanced Engine Performance Technician and is certified by the California Bureau of Automotive Repair as a Master Trainer. He has been with ALLDATA for nine years as an Editor.

©2013 ALLDATA LLC. All rights reserved. All technical information, images and specifications are from ALLDATA Repair. ALLDATA is a registered trademark and ALLDATA Repair is a mark of ALLDATA LLC. All other brand names and marks are the property of their respective holders.

Toyota and Prius are registered trademark names and model designations of Toyota Motor Corporation and/or Toyota Motor Sales, USA. All trademark names and model designations are being used solely for reference and application purposes.