Safety First:
* Disconnect the negative battery terminal. This prevents accidental shorts and electrical hazards.
* Allow the engine to cool completely. A hot engine can cause burns.
* Use jack stands. Never work under a vehicle supported only by a jack.
* Wear safety glasses. Broken parts can fly.
* Have the correct replacement belt. Get the correct size and type from an auto parts store, providing your vehicle's details.
Tools You'll Likely Need:
* Wrench(es): Appropriate sizes to loosen/tighten the belt tensioner(s) and any pulleys if needed. You may need a ratchet, socket set, and open-end wrenches.
* Socket wrench set: For removing and replacing nuts or bolts, if required.
* Pry bar (optional): Might be needed for stubborn belts.
* Gloves: To protect your hands.
* New fan belt: The correct size and type.
Steps:
1. Locate the fan belt and tensioner: The fan belt runs around the crankshaft pulley, water pump pulley, alternator pulley, and possibly others (power steering pump, air conditioning compressor). The tensioner is a device used to loosen the belt to allow for removal and installation. It's usually a spring-loaded mechanism. Identify the tensioner; it will have some kind of adjustment mechanism (usually a bolt or lever).
2. Loosen the belt tensioner: Use the appropriate wrench to loosen the tensioner. This will create slack in the belt. You might need to slightly turn the pulley or lever. *Be careful not to injure yourself with a spring-loaded mechanism*.
3. Remove the old belt: Once there's sufficient slack, carefully slip the belt off the pulleys.
4. Install the new belt: Route the new belt around the pulleys in the same order as the old belt. Make sure it's seated correctly on all pulleys.
5. Tighten the belt tensioner: Carefully tighten the belt tensioner to apply the correct tension. You'll usually feel some resistance as you tighten it. *Do not over-tighten the tensioner*. The belt should have a slight deflection (usually around 1/2 inch) when pushed in the middle between the pulleys. Consult your manual or the belt's packaging for specific tension recommendations.
6. Reconnect the negative battery terminal.
7. Start the engine and check for unusual noises or belt slippage. Listen carefully for any squealing or unusual sounds. If you hear problems, double-check the belt routing and tension.
Important Notes:
* Different engines have different configurations: The exact location of the tensioner and the method for loosening it will vary. Refer to a repair manual specific to your 1985 GMC Vandura 2500 with the correct engine.
* Some tensioners are automatic: Newer vehicles often have automatic tensioners that don't require manual adjustment. If yours is this type you might only need to loosen it slightly.
* Belt routing diagrams: A repair manual or online resource specific to your vehicle's engine will show you the correct routing of the belt. Get this right, or you could damage components.
If you're uncomfortable doing this yourself, it's best to take your vehicle to a qualified mechanic. This job is not overly complicated, but improper execution can lead to belt slippage, broken parts, or even engine damage. Always prioritize safety.
