how to check valve clearance

Daniel Parker

3 min read

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18-01-2025

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Meta Description: Learn how to check valve clearance on your engine! This comprehensive guide covers tools, steps, and troubleshooting for both beginners and experienced mechanics. Get the right clearances for optimal engine performance and avoid costly repairs. Includes detailed instructions and helpful illustrations.

Why Check Valve Clearance?

Valve clearance, also known as valve lash or tappet clearance, is the small gap between the valve stem and its actuating mechanism (rocker arm, lifter, or tappet). Maintaining the correct valve clearance is crucial for engine performance and longevity. Incorrect clearance can lead to:

• Poor engine performance: Too much clearance can cause a noisy engine and reduced power. Too little clearance can lead to burned valves or even catastrophic engine failure.
• Reduced fuel economy: Inefficient combustion due to improper valve timing will directly impact fuel consumption.
• Premature wear: Incorrect valve clearance accelerates wear on components like camshafts, lifters, and valves themselves.

Tools You'll Need

Before you begin, gather the necessary tools. The exact tools may vary slightly depending on your engine type and vehicle, but generally include:

• Mechanic's gloves: Protect your hands from grease and oil.
• Socket set and wrenches: For removing valve cover and other components.
• Feeler gauge set: This is essential for measuring the valve clearance.
• Torque wrench: To tighten bolts and nuts to the manufacturer's specifications.
• Owners manual: Consult your vehicle's service manual for specific instructions and clearance specifications. This is crucial; every engine is different!
• Jack and jack stands: Safely lift the vehicle if necessary for better access.
• Clean rags or shop towels: For cleaning up oil spills and keeping things tidy.

Step-by-Step Guide to Checking Valve Clearance

The process for checking valve clearance involves several steps and requires patience and attention to detail. Always refer to your vehicle's service manual for specific instructions and clearance specifications. These instructions offer a general overview:

1. Preparation:

• Safety First: Disconnect the negative battery terminal before starting any work on your vehicle's engine. This prevents accidental shorts.
• Vehicle Positioning: Ensure your vehicle is safely parked on a level surface, with the parking brake engaged. Use jack stands if you need to lift the vehicle.
• Engine Cool Down: Let the engine cool completely before starting. Hot engines are dangerous to work on.

2. Accessing the Valves:

• Locate Valve Cover: Identify and remove the valve cover. This often requires removing other components, like intake manifolds or air filter housings. Your owner's manual will guide you.
• Clean the Area: Thoroughly clean the valve cover area to prevent dirt or debris from entering the engine.

3. Measuring Valve Clearance:

• Identify Valves: Locate the intake and exhaust valves for each cylinder. Your owner's manual will show a diagram.
• Rotate the Engine: Rotate the engine crankshaft using a wrench on the crankshaft pulley or a socket on the crankshaft bolt. This aligns the valves so you can check the clearance for each valve in turn. Your manual will explain how to do this properly; improper rotation can cause damage.
• Insert Feeler Gauge: Carefully insert the appropriate feeler gauge between the valve stem and rocker arm (or other actuating component). The gauge should slide smoothly but with some resistance.
• Check Clearance: The feeler gauge should fit snugly, not too loose or too tight. Compare your measurement to your vehicle's manufacturer-specified clearance.

4. Adjusting Valve Clearance (If Necessary):

• Adjustment Methods: Valve adjustment methods vary significantly depending on the engine design. Some engines use shims, others use adjusting screws. Your owner's manual will detail the correct procedure.
• Precise Adjustments: Make small, precise adjustments as needed to achieve the correct clearance.
• Re-check Clearance: After making adjustments, re-check the clearance with the feeler gauge.

5. Reassembly:

• Replace Valve Cover: Carefully replace the valve cover and tighten the bolts to the manufacturer's specified torque.
• Reconnect Battery Terminal: Reconnect the negative battery terminal.
• Test the Engine: Start the engine and check for any unusual noises.

Troubleshooting Common Issues

• Incorrect Clearance: If the clearance is significantly off, you might have worn components, such as a worn camshaft lobe or lifter.
• Bent Pushrods or Lifters: These can cause inconsistent clearance and should be inspected carefully.
• Unusual Noises: If you hear unusual noises after adjusting the valves, re-check your work.

Conclusion

Checking valve clearance is a critical maintenance task for ensuring optimal engine performance and longevity. While it may seem daunting, following these steps carefully and referencing your vehicle's service manual will help you successfully check and adjust your valve clearances. Remember, if you're uncomfortable performing this task yourself, consult a qualified mechanic. Regular valve clearance checks are a key part of preventative engine maintenance and help prevent costly future repairs.