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As you know, spark plugs are very important components of an engine that needs changing after certain usage. In an auto shop, you will see a mechanic using a torque wrench for tightening spark plugs. That begs the question: do you need a torque wrench for spark plugs if you want to tighten them yourself at home?
The short answer is yes.
You need a torque wrench for tightening spark plugs to the manufacturer’s torque setting. But if you are handy with a traditional ratchet and spark plug socket, you can tighten engine spark plugs without a torque wrench. The process involves initial hand tightening and a solid half turn (180 degree).
Although this method of tightening may vary depending on the spark plug size and condition, the concept stays the same. So be sure to look at the owner’s manual for exact turn guidance and other helpful instructions for your reference.
If you are still unsure how to tighten the spark plug on your own, don’t worry it’s not rocket science but you have to be very careful. Below you will find all the helpful and related information about spark plugs, tightening guidance and so much more.
Why Do Torque Settings Matter For Spark Plugs?
Every car owner should know why spark plugs need specific torque settings. The main reason you need torque settings for your spark plugs is so that it doesn’t come loose due to vibration and other factors like heating and cooling. Internal piston combustion in the chamber also can cause your spark plug to become loose.
If any of these happens, there are great chances that you may face severe damage to your engine. Your engine performance will go down, you may feel your engine weakens a little bit, or at worst your engine may stall due to insufficient power supply. But this is not likely to be happening if you tighten the plugs to the correct settings.
Also remember that the correct torque to apply on spark plugs vary by plug diameters. Here is a handy list for you:
| Thread Diameter | Recommended Torque |
| 8 mm | 8 Nm (6 ft. lb.) |
| 10 mm | 10 – 12 Nm (7 – 9 ft. lb.) |
| 12 mm | 15 to 20 Nm (11 to 15 ft.lb.) |
| 14mm | 25 to 30 Nm (18 to 22 ft.lb.) |
| 18 mm | 35 to 40 Nm (26 to 30 ft.lb.) |
What Happens If You Have Loose Spark Plugs?
When you hand tighten a spark plug, there is a good chance of over-tightening, or out of fear you may leave it loose. With time and due to the trembling of the engine, even a well-tightened spark may become loose.
In the combustion chamber of an engine, there are a lot of things that happen in a split second. The air intakes, fuel spray, air compression, combustion along with the movement of the piston are vital processes in a car engine cylinder. A loose spark plug can disrupt the usual process introducing excess air as well as spilling fuel through the cracks.
This will definitely decrease the engine efficiency along with a plethora of complications like engine miss fire, and damage to the cylinder or piston. Your engine will also run hotter than usual and blink your engine check light. Apart from that the cylinder head and the plug thread may also wear in the process. That can be a very expensive fix from a professional repair shop.
What Happens If The Spark Plugs Are Too Tight?
In the same sense, if you tighten the spark plug too tight, there are also complications waiting on the other side. First of all, you will damage the cylinder head along with the spark plug thread. Due to heating, cooling, and vibration, the spark plug thread may crack without giving prior notice.
On top of that, you will also face all the problems that would happen with a loose spark plug. Through that crack, more oxygen will enter the chamber, and the efficiency of the compression will decrease significantly. Moreover, it would be very hard to remove the damaged spark plug and may cause further damage to the cylinder head.
What Type Of Torque Wrench Do I Need For Spark Plug
The most common type of torque wrenches is click type and beam design torque wrenches. Although they are both capable of exerting proper torque force up to the rated settings. Here are a few quick lines about the torque wrench types.
Beam Type Torque Wrench
Among them, beam design torque wrenches are the most cost-effective for beginners. Even though it’s very affordable, the accuracy of this torque wrench is highly accurate throughout the torque settings.
But there’s a catch, if your spark plugs happen to be on the rear side of the engine, it could be a bit hard to see. That will also result in under-tightening and improper fittings. But if you are just starting to build your tool inventory, beam-type is a great starter torque wrench.
Click Type Torque Wrench
Another most popular torque wrench you will see mechanics using is the click type torque. They are a bit expensive but have a higher torque range than the beam-type wrench. On the matter of accuracy, the click-type torque wrench has the most accurate of all torque wrench.
One problem people face with the click-type torque wrench is the torque range. The click type wrench is most accurate in the medium range settings. So if you need 7ft-lbs. torque on your spark plug buy an inch-pound torque wrench for the task. apart from that, the click type wrench is a perfect tool for spark plug installation.
What Size Torque Wrench Do I Need For Spark Plug
3/8 inch torque wrenches are more common for installing the spark plug. Depending on the vehicle model and spark plug type the required torque settings can be around 5-7 feet pounds.
Checkout the best torque wrench for spark plugs.
You will need to make sure the torque wrench you are going to buy has these torque settings in the middle for the most optimum force exertion.
Do You Need A Torque Wrench For New Spark Plugs?
If you have read the above points you should have an idea why you need a torque wrench for the spark plugs. And this applies to the new as well as the old one. You can easily find how much torque you will need for new, old, tapered, and spark plugs with a gasket in the owner’s manual.
Is It Safe To Hand Tighten Spark Plugs?
All things considered, hand tightening the spark plug is possible when you don’t have a torque wrench. But you should keep in mind that this is only a temporary solution. You should always check the torque setting from a shop or with a torque wrench from a friend later.
Installing a Spark Plug Without a Torque Wrench
The easiest way to install a spark plug without a torque wrench is by finger tightening and following with a half turn with the ratchet. More clearly, remove the old spark plug and clean the area as much as you can. Then gently place the new spark plug on the cylinder head with the spark plug socket. After that turn the socket with your fingers till you feel resistance. When that happens, place your ratchet on the socket and do a 180-degree turn for the final tightening.
When Do You Need to Change Your Spark Plugs?
Depending on the spark plug type, your ideal time for changing may vary. For example, iridium and platinum spark plugs have the most durability and service time. On the other hand, copper plugs have a standard lifespan. In general, the ideal interval between replacing a new spark is around 30,000 miles depending on your vehicle model. To know the exact interval, read through the owner’s manual.
Wrapping Up
At the end of the day, whenever the time comes for a new spark plug, a good torque wrench is your best bet to finish the job properly. Then again, you still have the hand tightening method to get you started without having to run to the hardware store for the torque wrench.