Broken Bolt Valve Cover – Causes And How To Fix It

Broken Bolt Valve Cover – Causes And How To Fix It

The valve cover plays a vital role in securing the upper section of the engine. In addition, this component keeps the engine oil in check.

As the name suggests, this is the cover that you will find along the valve train section.

If you discover that oil is leaking from the top of your engine, then the chances are that your valve cover is loose.

Broken Bolt Valve Cover Causes & How To Fix It

Oil leakage along the valve train can cause minor and very major damages.

The valve cover relies on a valve cover gasket and bolts, which snap very quickly, to attach to the cylinder head and maintain a tight seal.

Similarly, there is nothing as wrong as driving with a broken bolt valve cover.

As long as you do not see oil leakage at the top of your engine, then you are fine driving your car to the garage for replacement.

Reasons Why Your Car Has A Broken Bolt Valve Cover

There are several reasons you will end up with a valve cover with a broken bolt. One of the common issues is using the wrong toque when fixing them back.

The second reason is the failure to use a tightening sequence, straining the bolt.

The valve cover bolt can break into three sections: the head, the shank, and the thread sections. Some of the bolts are long, while others are short.

Wrong Or Too Much Torque

Most car owners would prefer polishing their valve covers or replacing the valve gaskets without professional assistance.

But sometimes, the DIY fixes can put you into a lot of trouble, especially when you are putting the bolts back.

When placing back your valve cover bolts, they need to be in the correct order and the recommended torque value (43 – 78 inch-lbs.).

Over-tightening the valve cover bolts can form cracks that eventually break. The disadvantage of using a torque wrench is that it may fail to click at the set value.

A driver may be an excellent tool to tighten your valve cover bolt with a snug fit.


If you still insist on doing it yourself, you’ll need to visit a local junk car to pillage the bolts of an old car.

Before you tighten the bolts, you should determine whether tightening the bolts requires you to use newton meters, INCH pounds, or foot-pounds.

For this kind of task, you can tighten the bolt by hand and finish up with the help of a screwdriver socket or torque wrench.

Most experienced auto dealers can tighten the bolts by feel. With a torque wrench, you can tighten the bolt to 7 ft/lbs.

You can also use a 1/4″ drive ratchet to avoid overtightening the bolt. You can quickly feel when the bolt is tight enough with a ratchet.

On the other hand, you can still visit an auto shop and get the broken bolt valve cover replaced with new ones.

Failure To Use A-Bolt Tightening Sequence

Snugging down the valve cover bolts in the wrong order can make them break.

Bolt tightening sequence is essential, especially where elastic interactions can form due to pre-load lost in a bolt.

Failure to tighten the bolts in a symmetrical pattern can lead to detrimental failure.

Conversely, the valve cover bolt may experience plastic deformation and fail when the pre-load is too high.


The best way to bolt back the valve cover is to ensure that the valve cover and the gaskets are correct.

The next step will be to put all the bolts in their slots until they sit against the valve cover.

Then tighten the bolts in an alternating pattern, starting in the middle and working your way outwards, ensuring that the torque remains at 7 ft/lbs.

Broken Bolt Valve Cover

How To Remove Broken Bolt Valve Cover

Before replacing a broken bolt for the valve cover, you need to remove the damaged part from the hole.

Depending on the damage, you will find various ways you can use to remove a broken bolt valve cover.

Here are the tools you may need to remove a broken bolt valve cover:

  • Drill machine
  • Screw Extractor set (left hand)
  • Tap set
  • Center punch
  • 1/8″ bit and 3/16″ drill bits (left hand)
  • Die grinder or a variable Speed Rotary Tool
  • PB blaster or WD-40
  • Socket wrench or pliers
  • Vice grip
  • Tap sockets

Here are some techniques you can use to remove a broken bolt valve cover:

Tapping The Head Of The Broken Bolt Valve Cover

You can try trapping the head of the remaining shank and thread it out. This method is applicable when the bolt snaps along the shank area.

Drilling And Re-Tapping

You can also drill it out and re-tap the threads. This method is recommendable when the bolt breaks at the thread section or, as they call it, a snapped flush.

Drill And Extract

Use a center punch to form a dimple or mark the center of a point to position the drill bit.

Next, drill a hole into the broken bolt and use a bolt extractor or tap with a socket wrench or pliers as the handle.

When the extractor holds and turns the tap handle counterclockwise, you can use a little heat with a torch and PB blaster or WD-40 spray to make the work easier.

Extra care is required so that you don’t also break the tap when turning. In addition, when you drill, ensure that the shavings do not end on the head or, worse, the crank.

This method is not suitable for bolts with high torque specs. In addition, you need to have experience in bolt extraction to use this method.

Otherwise, getting it wrong can risk damaging the engine casting.

Grip And Loosen

The shank is exposed if the valve cover bolt breaks at the head. In this case, you can use a pair of vice grips to clamp it and turn counterclockwise to loosen it.

Then, grab at the base of the bolt for a much firm grip.

Weld A Nut And Twist

Another method to use when you break the bolt near the head is to tack weld a nut to the stub of the broken bolt and then back the bolt out.

This method is recommendable if you wish to protect the threads and avoid hitting the sides of the hole when drilling.

Re-Drill & Tapping The Hole

The last method you would use is to get in there with a die grinder, hog out the whole area, fill the hole with weld, then re-drill, and lastly, tap to get the threads back.

It is challenging to replace a broken bolt from the rear valve cover, which is difficult to access with a drill.

In case you are dealing with bolts that have rust on them, you will need to use a PB blaster to loosen it more and get moving.

Take Away

The last option for removing a broken bolt valve cover would be to contact your mechanic and have them look at the problem and recommend a solution.

You may choose to drive the car or tow it to the machine shop and have professionals solve the problem for you.