Broken Bolt On Valve Cover – Troubleshooting & Repairing guide

Whether you’re a car enthusiast or a concerned vehicle owner, a broken bolt on a valve cover can be a frustrating and worrying problem. It can cause oil leaks, engine performance issues, and potentially costly repairs. But don’t be alarmed! As we will see in this article, repairing a broken bolt is doable.

So how do I fix a broken bolt on valve cover? First, carefully remove the valve cover to access the broken bolt. If the bolt is partially broken, use pliers or vice grips to unscrew the remaining part carefully. If the bolt is completely broken, you’ll need to use a drill with a metal drill bit to make a small hole in the center of the bolt. Then, using a bolt extractor tool, grip the bolt and turn it counterclockwise to remove it.

Continue reading for more information on replacing a broken bolt on a valve cover. We’ll also review various techniques and valuable maintenance tips for troubleshooting and repairing a broken bolt on a valve cover.

How Does A Broken Bolt Result On A Valve Cover?

A broken bolt on the valve cover can occur for several reasons. Understanding these causes can help you avoid similar problems in the future. Here are the two major reasons:

1. Over-Tightening During Installation

Applying excessive force when tightening the bolts on the valve cover can lead to bolt breakage. When tightening the bolts, it is critical to use the correct torque value, which typically ranges from 43-78 inch lbs. Use a torque wrench set to 7 ft/lbs or a one-fourth-inch ratchet.

2. Wrong Bolt Tightening Sequence

Valve covers typically have multiple bolts that must be tightened in a specific sequence. Failing to follow the proper tightening sequence can result in uneven pressure distribution, leading to bolt stress and potential breakage.

To avoid this, tighten in an alternate pattern, starting in the center and going outwards. To assist in securing the valve cover and avoid overtightening, utilize a torque of 7 ft/lbs.

Signs Of A Broken Bolt On Valve Cover

Here are some key signs that show you have a broken bolt:

  • Oil Leaks:

If you observe oil pooling around the valve cover region or see visible drips or stains beneath the engine, it could suggest a damaged seal caused by a broken bolt. Leaking oil may have a burnt smell and a deeper hue than new engine oil.

  • Poor Acceleration/ Decrease In Engine Performance:

The valve cover is responsible for sealing and protecting the valves, camshafts, and other internal components. If a bolt is broken, it can compromise the integrity of the valve cover, allowing dust, dirt, and debris to enter the engine compartment.

This can contaminate the engine oil, leading to increased friction and wear on internal components. This will ultimately impact the engine’s performance which results in reduced engine power and sluggish acceleration.

  • Engine Misfires or Rough Running:

A damaged bolt might cause improper sealing, allowing air into the engine. This can cause the air-fuel mixture to be disrupted, resulting in engine misfires or a rough-running engine. You may notice hesitancy, stopping, or a significant decline in performance.

  • Unusual Engine Noises:

A broken bolt might cause the valve cover to become loose or shift slightly, resulting in irregular rattling or ticking sounds. This noise is often more noticeable during acceleration or when the engine is under load. It indicates a possible problem with the valve cover assembly that has to be addressed.

  • Valve Cover Itself Appears Dirty And Covered In Dust Or Grime:

This happens because a broken bolt can cause gaps or openings in the valve cover’s seal, allowing external elements to enter. These contaminants accumulate on the valve cover over time, indicating a possible problem with a broken bolt.

Tools and Materials Required For Valve Cover Bolt Repair

Gathering the necessary tools and materials is essential before embarking on the repair process for a broken bolt on a valve cover. Here is a comprehensive list of tools and materials you will need for various techniques:

  • Vice Grip: This provides a strong and secure grip on the broken bolt, making it easier to turn and extract.
  • Drill Machine: A drilling machine is necessary for drilling into the broken bolt.
  • Center Punch: This tool creates a small indentation or mark on the broken bolt. This indentation helps guide the drill bit and prevents it from slipping off the bolt during drilling.
  • Tap Set and Tap Sockets: After removing the broken bolt, a tap set creates new threads in the drilled hole.
  • Screw Extractor Set (Left Hand): The left-hand threaded extractors are designed to grip and remove the broken bolt by rotating it counterclockwise. The set typically includes a range of extractor sizes to accommodate different bolt diameters.
  • Socket Wrench/Pliers: These are useful for turning and removing bolts. Choose the appropriate size and type of wrench or pliers that fit the bolts securely.
  • 1/8-inch Bit and 3/16-inch Drill Bit: These drill bits are commonly used to drill holes into the broken bolt. The 1/8-inch bit is usually used as a pilot hole, while the 3/16-inch bit is used for drilling the central hole.
  • WD-40: WD-40 or a similar penetrating oil lubricates and loosens the broken bolt. Apply the oil and let it sit for a few minutes before attempting to remove the bolt.

Different Techniques For How To Remove A Broken Valve Cover Bolt

When a valve cover bolt breaks, you must replace it with a new one. However, before replacement, you must remove the remaining part of the broken bolt from the hole. Here are different methods you can use depending on the severity of the bolt damage.

Procedure 1: Vice Grip Technique

  1. If the broken bolt has enough exposed surface, use a vice grip or locking pliers to grip the bolt firmly.
  2. Apply steady pressure counterclockwise to loosen and remove the broken bolt.
  3. If the bolt is difficult to grip or turn, use penetrating oil like WD-40 to lubricate and facilitate easier extraction.

Procedure 2: Using a Screw Extractor Set

  1. Insert the punch into the bolt hole and strike its back with a hammer. Mark the center of the broken bolt to create a guide for drilling.
  2. Start Drilling almost on the center of the bolt.
  3. Select an appropriately sized left-hand threaded screw extractor from the set.
  4. Carefully insert the screw extractor into the drilled hole, ensuring a secure fit.
  5. Use a socket wrench or pliers to turn the screw extractor counterclockwise, applying steady and gradual force.
  6. The left-hand threads of the extractor will grip the broken bolt and gradually loosen it, allowing for removal.

Procedure 3: Welding Method

  • This technique is suitable for bolts with a portion exposed above the surface.
  • Weld a nut onto the broken bolt using a welding machine.
  • Allow the welded assembly to cool down, and then use a wrench or socket to turn the bolt counterclockwise to remove it.

Procedure 4: Drilling and Tapping

This method is effective when you have a snapped flush. A snapped flash is when the bolt breaks in the threading section.

  1. Begin by center punching the broken bolt and drilling a pilot hole with a 1/8-inch bit.
  2. Gradually increase the drill bit size to 3/16 inch, drilling a larger hole through the broken bolt.
  3. After removing the broken bolt, select an appropriate tap from the tap set. The tap should match the size and thread pitch of the original bolt.
  4. To reduce friction, apply lubricating oil to the tap, such as WD-40.
  5. Insert the tap into the newly drilled hole and turn it clockwise to cut new threads.
  6. Turn the tap with tap sockets and a socket wrench until the desired thread depth is achieved, and remove the damaged bolt.

Here is a video to help you Removing broken valve cover bolt:

Additional Considerations and Maintenance Tips

These tips will help ensure a successful repair and prevent future issues. Here are some key points to consider:

●    Inspect Other Bolts and Fasteners

While addressing the broken bolt, take the opportunity to inspect the condition of other bolts and fasteners on the valve cover. Check for signs of wear, corrosion, or damage. Tighten any loose bolts and replace any damaged or worn fasteners to maintain the integrity of the valve cover assembly.

●    Use Proper Torque Specifications

Following the manufacturer’s recommended torque specifications is critical when installing a new bolt or reassembling the valve cover. Overtightening can cause bolt failure or damage to the valve cover, while under-tightening can cause oil leaks or inadequate sealing.

●    Consider Upgrading to Stainless Steel Bolts

If the broken bolt was caused by corrosion or wear, consider replacing it and the other bolts on the valve cover with stainless steel bolts. Stainless steel is more corrosion-resistant, resulting in increased durability and longevity.

●    Perform Regular Maintenance

Regular maintenance on your vehicle is essential to prevent issues such as broken bolts. This includes following the manufacturer’s recommended service intervals, which may involve inspecting and tightening bolts, checking for leaks, and replacing gaskets or seals as needed.

●    Seek Professional Assistance If Needed

While DIY enthusiasts can perform many broken bolt removal techniques, some situations may necessitate professional assistance. If you encounter difficulties during the removal process or lack the necessary tools and experience, it is recommended that you consult a professional mechanic or automotive technician.

Also, when replacing a damaged bolt with a new one, it is recommended to seek professional assistance.


Dealing with a broken bolt on a valve cover can be difficult, but with the right techniques and precautions, it is a fixable problem. Understanding the causes of a broken bolt, recognizing the symptoms, and employing appropriate removal methods will allow you to successfully resolve this issue and restore the functionality of your valve cover.

Preventive measures, such as using proper torque specifications, can help prevent future bolt failures and ensure the longevity of the valve cover assembly. Regular maintenance and seeking professional assistance are also essential for maintaining a well-sealed and efficiently functioning valve cover.

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