Dennis Shortino, ALLDATA Editor
and Jeff Webster, ALLDATA Technical
As 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
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
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 procedures 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.
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
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.
Review safety procedures in ALLDATA® Repair S3000SM before
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.
Remove the inverter w/converter assembly following factory
and/or industry standard approved practices. NOTE: Do NOT replace the inverter.
Support the hybrid transaxle assembly by using a transmission
Remove and replace the engine mounting insulator LH (No. 3
Engine Mounting Bracket) (Figure 1).
A. Remove the engine mounting insulator sub-assembly LH
B. Remove two nuts from engine mounting insulator
C. Replace the engine mounting insulator LH with the NEW
(P/N 12372-21111) (Figure
D. Tighten the 2 nuts. Torque: 47 ft lb (64 Nm, 640 kg cm)
E. Attach the engine mounting insulator sub-assembly LH on
vehicle. Torque: 59 ft*lb (80 Nm, 800
Install the inverter w/converter assembly following factory
and/or industry standard approved practices.
Road test to verify proper operation of the vehicle.
For more information on OE repair information, please visit
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 9 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 9 years as an Editor.
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.