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GM Pontiac Grand Prix Serpentine Belt Replacement Guide
A pictures illustrated guide for replacing the serpentine (accessory) belt on a General Motors 3800 Series II 3.8L V6 engine.

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This "how to" automotive repair guide was specifically written to assist owners of the 1997-2003 General Motors Pontiac Grand Prix GTP in replacing the serpentine (accessory) belt. Owners of other GM cars with engines similar to the 3800 Series II 3.8 Liter V6 may also find the guide to be useful. These other vehicles include the following: Buick Park Avenue Ultra, Olds Eighty-Eight LS, Oldsmobile Eighty Eight LSS, Olds Ninety-Eight, Pontiac Bonneville (SLE, SSE, SSEi), Buick Riviera, Buick Regal (GS, GSX, SLP), Chevy Impala SS, and the Chevrolet Monte Carlo SS. I am not a professional mechanic. I assume no responsibility for damage to your vehicle, persons, property or pets. If you have any doubts, please consult an ASE certified mechanic. Please proceed with caution at your own risk.

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GM 3800 Series II 3.8L V6
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New Dayco Serpentine Belt

 
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Belt Routing Diagrams

 

After redlining the engine through a turn a few days ago, I heard a series of loud noises coming from the engine bay. I popped the hood and saw that nearly half of the serpentine belt had broken off.

Luckily, the other half of the "accessory" belt held together long enough to drive to Advance Auto Parts and pick up a new one. The new belt that I purchased is a Dayco brand Poly Rib model # 5060918, which cost about $40.

Engine belts usually last anywhere from 60,000 miles to upwards of 100,000 miles. They should be inspected at least twice a year for cracks, fraying, glazing, or other signs of significant wear.

The tools needed to complete this procedure include the following: 15mm socket, 13mm socket, 10mm socket, 8mm socket, ratcheting wrench, and a long handled socket wrench.

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Supercharger Belt
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Half Of Serpentine Belt
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Torn Up Hood Mat

To remove either the serpentine or the Supercharger Belt, it helps to first remove the coolant overflow tank. My car has a Buick STB (strut tower brace) installed in the engine compartment, so I had to detach the left side of it before removing the coolant overflow tank. The Buick STB requires a 13mm socket and ratcheting wrench to remove the two passenger side bolts.

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13mm Socket & Wrench
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Buick STB Bolts
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Buick Strut Tower Brace

If your car is naturally aspirated, such as the Pontiac Grand Prix SE or GT, skip ahead to the instructions after the supercharger belt removal located below picture # 40.

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Removing Buick STB
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10mm Socket & Wrench
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Coolant Overflow Bottle

The coolant overflow bottle is held in place by two thin 10mm nuts. Once the coolant bottle is pulled up out of the engine bay, detach the black rubber hose from its side. To prevent any coolant from leaking out of the hose, I covered it with a plastic bag and a rubber band. Be careful when you move the coolant bottle because the fluid can splash out of the lid and the tube on the side.

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Removing Coolant Bottle
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Detaching Coolant Hose
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Coolant Bottle Removed
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Coolant Hose Sealed
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Engine Bay Brace
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13mm Socket

I had originally decided to remove the battery and the passenger side engine brace to make accessing the belts easier. This may have not been necessary as there is plenty of room to reach the belts and pulleys once the coolant overflow bottle is out of the way.

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Removing Engine Brace
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Rubber Mallet
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Two Small Lower Bolts
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One Large Upper Bolt
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Releasing Wire Harness
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Brace Removed


 
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8mm Socket
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Negative Battery Terminal
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Removing Battery Terminals

For extra safety, I removed both battery cables and covered the side mounted battery terminals with blue painters tape. I didn't want to risk accidentally putting a wrench across the two terminals and getting a shock.

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Battery Terminals Covered
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15mm Socket
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Routing Diagram

To remove the serpentine belt, I first had to remove the supercharger belt. Study the routing diagram on your car, or the one I took a picture in the row above.

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15mm On SC Tensioner
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Releasing Tension On SC Belt
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Loosened SC Belt

The smooth tensioner pulley for the supercharger belt is located below the supercharger pulley towards the front of the car. It is just behind a black ribbed idler pulley. To loosen the supercharger belt, place the 15mm socket and long handled socket wrench on the SC belt tensioner pulley. Pull the wrench towards the front of the car to release the tension on the supercharger belt. While holding the wrench in this position, slip the supercharger belt off the supercharger pulley. If you can't slip it off, rotate the wrench more towards the front of the car to further loosen the belt.

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Supercharger Belt Off
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Pulling Off SC Belt
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To completely remove the supercharger belt, pull it off the crank shaft (largest & lowest pulley), the tensioner and the two idler pulleys (3.5" smooth metal & 3" ribbed plastic).

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Old Supercharger Belt
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Pits & Cracks
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Old Serpentine Belt
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"Accessory" Belt
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Belt On Alternator
The tensioner pulley for the serpentine or "accessory" belt is located directly below the alternator. It is a smooth 3" metal pulley. To release the tension on the serpentine belt, place the 15mm socket on the pulley and push the long handled socket wrench towards the rear of the car.
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15mm On Tensioner Pulley
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Push Towards Rear of Car
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Tension Released Off Alternator

With the tension released, you can pull the old serpentine belt off the alternator and then off the other pulleys. The serpentine belt is routed around or over the water pump, crank shaft, air conditioner compressor, the power steering pump, and the tensioner.

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Old Serpentine Belt
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Cracks, Pits, Wear
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New Serpentine Belt

Now is a good time to check all of the idler, tensioner and other pulleys to see that they spin freely. The large crank shaft pulley is the only one you shouldn't be able to spin by hand. If any idler or tensioner pulley does not rotate easily with the flick of a finger, you should replace them now before they seize. I had to replace both the Supercharger Belt Idler Pulley and the Serpentine Belt Tensioner Pulley. For instructions on how to change those pulleys, click on the preceding links.

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Power Steering Reservoir
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Idler & Tensioner Pulleys
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Checking Pulleys
I also took this opportunity to check the level in the Power Steering Fluid Reservoir, and top it off with some "stop leak" PS fluid since the power steering pump has a very slow leak.
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$40 - Advance Auto
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Both Belts Removed
After checking and replacing any worn out pulleys, you can install the new Dayco 5060918 Poly Rib Serpentine Belt. First study the routing diagram. Also keep in mind that any smooth pulley gets the smooth side of the belt and any ribbed pulley should be wrapped by the ribbed side of the belt.
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Belts Routing Diagram
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New Belt On Crank
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The serpentine belt first goes around the inner part of the crank shaft (ribbed, largest, lowest), then around the water pump, tensioner, power steering, and the A/C. Pull the serpentine belt up towards the alternator and hold it with one hand. With your other hand, place the 15mm socket and long handled wrench on the tensioner pulley just below the alternator. Push the long handled wrench towards the rear of the car to release the tension on the belt and then slip it over the alternator pulley.
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15mm On Tensioner
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Pushing Towards Rear
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New Belt On Alternator

Double check the routing diagram and the serpentine belt to make sure that it is routed properly over the correct pulleys. Make sure that every smooth pulley is against the smooth side of the belt and every ribbed pulley is against the ribbed side of the belt.

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Checking Belt Routing
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Putting on SC Belt
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SC Belt On Crank Shaft

If you're car is naturally aspirated (doesn't have a supercharger) you're done replacing the serpentine belt. Skip past the next block of text.

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Holding SC Belt
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Pull SC Tensioner Forwards
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Slip SC Belt On SC Pulley
Now that the serpentine belt is in place, we can re-install the supercharger belt. Route the supercharger belt over or around the outer part of the crankshaft pulley, the two idler pulleys and the tensioner pulley. Hold the supercharger belt near the supercharger pulley with one hand. With your other hand, place the 15mm socket and long handled wrench on the tensioner pulley located just below the SC pulley and towards the front of the car. Pull the long handled wrench towards the front of the car to loosen the belt and then slip it over the supercharger pulley. Check that the belt is routed properly with the smooth side against every smooth pulley and the ribbed side against the ribbed pulleys.
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Serpentine & SC Belt Installed
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Re-Attach Coolant Hose
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Re-Attach Battery Terminals
The last steps are to re-install the hose on the coolant overflow bottle and re-install the bottle itself. Then re-attach the Buick STB if your car is equipped with one. If you've done everything right, your engine should look and sound like mine in this video clip - GM 3800 Series II Engine Running Video.
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Re-Attach Coolant Bottle
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Re-Attach Buick STB
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Re-Install Engine Bay Brace

For more of my automotive "how-to" instruction guides, click on the following links: Pontiac Grand Prix Supercharger Belt Replacement Guide, GM 3800 Series II Tensioner & Idler Pulleys Replacement Guide, Pontiac Grand Prix Front Brake Pads Replacement Guide, Grand Prix Rear Brake Pads Replacement Guide, Pontiac Grand Prix Brake Lines Bleeding Guide, GM 3800 Series II Power Steering Fluid Maintenance Guide, Pontiac Grand Prix Alternator Replacement Guide, Pontiac Grand Prix PCV Valve Replacement Guide, Grand Prix TCS/ABS/SES Troubleshooting Guide, GM Pontiac Grand Prix Power Window Motor & Regulator Replacement Guide, GM Wheel Bearing Hub Replacement Guide, GM Pontiac Grand Prix Engine Oil Change Guide, Eaton M90 Supercharger Oil Change Guide, and the Tail Light or Headlight Condensation Removal Guide.
 

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