engine

Idler Pulley

for 2017 Dodge Viper 8.4L V10 · RWD

Difficulty

Easy

Time

1.0 h

Tools

Steps

✓Fact-checked. Built from OLP's spec database, then independently fact-checked line by line with every correction applied. Master-tech sign-off by Chris Hackleman is queued. Cross-check torque values against the factory manual, and stop if anything looks unsafe. How our data is made.

Removal and replacement of the serpentine belt system idler pulley on the 8.4L V10 engine, including belt removal and reinstallation.

Warnings

⚠Allow engine to cool completely before beginning work. Engine components may retain heat for extended periods.

⚠Belt tensioner is spring-loaded and stores significant energy. Maintain firm control when releasing or applying tension.

ℹ️The 8.4L V10 has multiple idler pulleys in the serpentine belt system. Verify which pulley requires replacement before beginning work.

Tools required

15mm socketEssential

3/8" drive ratchetEssential

Serpentine belt tool or 18mm wrenchEssential

Torque wrenchEssential

Shop light

Belt routing diagram photo/sketch tool

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Parts

Idler pulley assembly × 1 — Use OEM specification

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Preparation

Park vehicle on level ground and engage parking brake
Allow engine to cool completely
Open hood and secure in raised position
Photograph or sketch the serpentine belt routing for reference during reinstallation
Visually inspect all pulleys to confirm which idler pulley requires replacement

Procedure

1
Remove serpentine belt
Locate the belt tensioner on the front of the engine. Using a serpentine belt tool or appropriate wrench/socket on the tensioner, rotate the tensioner in the direction that relieves belt tension (verify direction against the vehicle's belt routing/tensioner marking) to release belt tension. While holding tension released, slide the belt off one of the pulleys (typically easiest at the alternator or idler pulley). Carefully release the tensioner back to its rest position. Remove the belt from remaining pulleys and extract from engine bay. Note: Locate the belt tensioner on the front accessory drive of the engine (confirm exact position by visual inspection).
2
Locate target idler pulley
Identify the specific idler pulley to be replaced. The 8.4L V10 has one or more idler pulleys in the accessory drive; identify the specific idler pulley to be replaced by visual inspection. Idler pulleys are typically mounted with a single center bolt threaded into a bracket or the engine. Verify the pulley spins freely without wobble or noise before proceeding with replacement.
3
Remove idler pulley mounting bolt
Using the appropriate socket and ratchet (verify bolt head size on the vehicle), remove the center bolt securing the idler pulley to the engine block or bracket. The bolt threads directly into the engine block or bracket. Remove the bolt completely and retain for comparison with new hardware if replacement bolt is included with new pulley.
4
Remove idler pulley
Pull the idler pulley assembly straight off the mounting stud or boss on the engine block. If the pulley is stubborn, gently wiggle while pulling to free it from the mounting surface. Inspect the mounting surface for debris or damage.
5
Prepare mounting surface
Clean the idler pulley mounting surface on the engine block using a clean rag. Remove any dirt, oil residue, or old thread sealant from the mounting bolt hole threads. Inspect the mounting boss or stud for damage or excessive wear.
6
Install new idler pulley
Position the new idler pulley onto the engine block mounting boss, ensuring proper alignment. Verify the pulley rotates freely before securing. Start the mounting bolt by hand to ensure proper thread engagement and prevent cross-threading.
7
Torque idler pulley bolt
Using a torque wrench and the appropriate socket, tighten the idler pulley mounting bolt to the factory-specified torque (verify against the 2008 Viper 8.4L V10 service manual before finalizing). Verify the pulley still rotates freely after torquing and has no lateral play or wobble.
ℹ️Torque specification is typical for this application but should be verified against factory service manual if available.
8
Reinstall serpentine belt
Using your belt routing diagram or photo, route the new or existing serpentine belt around all pulleys except one (typically leave the alternator or an idler pulley for last). Ensure the belt is properly seated in all pulley grooves with ribs aligned. Using the serpentine belt tool or 18mm wrench, rotate the tensioner clockwise to create slack, then slip the belt onto the final pulley. Carefully release the tensioner to apply proper tension to the belt.
9
Verify belt routing and tension
Visually confirm the serpentine belt is correctly routed according to the belt routing diagram (typically found on the fan shroud or radiator support). Verify the belt is properly seated in all pulley grooves with ribs fully engaged. Check that the belt has proper tension and is not twisted anywhere in the routing path.

Reassembly

Ensure all tools and parts packaging are removed from engine bay
Double-check serpentine belt routing matches factory diagram

Verification

Start the engine and listen for unusual noises from the belt or pulley area
Observe the serpentine belt during idle to confirm smooth operation without slipping or vibration
Verify the new idler pulley rotates smoothly without wobble or noise
Check belt alignment across all pulleys while engine is running
Allow engine to reach operating temperature and recheck belt operation for any issues that appear when warm