* Worn or Damaged Belt: The most likely cause is a worn or cracked serpentine belt. Inspect it carefully for cracks, fraying, glazing (shiny, smooth surface), or other damage. If it's damaged, replace it.
* Worn Tensioner Pulley: The automatic tensioner itself can fail. It might not be providing enough tension, or it could be seized. A failing tensioner will often make noise (whining, clicking).
* Worn or Damaged Pulley(s): Check all the pulleys (alternator, power steering pump, water pump, etc.) for wear, damage, or bearing noise. A pulley bearing that's going bad can cause belt slippage.
* Other Issues: In rare cases, something might be obstructing the belt or preventing proper alignment. However, this is less common.
How to proceed:
1. Visual Inspection: Start by carefully inspecting the serpentine belt and all the pulleys. Look for any obvious damage or problems.
2. Listen for Noises: With the engine running, listen for any unusual noises from the area of the belt and pulleys. Whining, squealing, or clicking are all signs of a problem.
3. Replace the Belt (if needed): If the belt is worn or damaged, replace it with a new one. This is often the simplest and cheapest solution. Always use a belt of the correct size and type specified by Honda for your model. Consult your owner's manual or a parts store for the correct belt part number.
4. Check Tensioner (if you suspect a problem): Assessing the tensioner properly requires some mechanical knowledge. If you're not comfortable doing this yourself, take it to a mechanic. A failing tensioner may need to be replaced.
5. Professional Help: If you're not comfortable with automotive repairs, it's best to take your Civic to a qualified mechanic for diagnosis and repair. Attempting to improperly "fix" a slipping belt can lead to further damage.
In short: You don't adjust the belt tension. You replace the belt or other faulty components.
