When you’re driving, the last thing you want to happen is for the spark plug to shoot out of your engine.
But what does it mean when you experience the unexpected, and the spark plug is out of your engine? How do you fix it? More importantly, how much is it going to cost you??
Before you see a mechanic or try to fix it yourself, take a look at this guide. There is so much misinformation regarding spark plug blowouts, and we want to make sure to get good information out there to avoid getting taken advantage of by a shady mechanic.
What is a Spark Plug Blow Out?
A Ford vehicle has a unique problem with spark plug blowout. Just so we are on the same page, the spark plug is blowing straight out of the cylinder head.
Most of the time, the spark plug will remain attached to the coil wire, but because it is no longer in the combustion chamber, it is not functioning at all. Therefore, this is a well-known problem for specific vehicles, mainly Ford vehicles, specifically their 4.6L, 5.4L, and 6.8L engines.
However, while this is certainly a far more common problem found in these vehicles, it is not the only kind of vehicle that can suffer from a similar problem. And because it is frequently a function problem found with the Ford vehicles, there are readily available repair kits out there.
If you are faced with a different kind of vehicle suffering a similar issue, you may have a little more difficulty finding the correct repair kit.
What Causes a Spark Plug to Blow Out?
There are a few potential causes of spark plug blowout, but the most common is that the spark plugs were slightly loose when you installed them.
Over time, the spark plugs will back out more, and at some point, there will not be enough threads to hold them in place.
When this happens, the spark plugs will wind up shooting out of the holes when the engine is running. Compounding this issue is that some, but not all, of the maintenance manuals for older Ford vehicles list a torque specification that is a bit low.
They may state a torque specification of around 20 ft-lbs., whereas newer service manuals and sources recommend between 28 and 30 ft-lbs. If you go with the lower torque specification, whether you believe it or not, there is a risk of the spark plug blowing out of the cylinder head at some point.
Sure, there could be excessive pressure inside the combustion chamber, but this is only a problem if you have performance parts on your vehicle. Even then, there are freeze plugs that should crack before spark plugs.
As a side note, some authors claim that if you over-torque your spark plugs, there is a risk that they could blow out of the cylinder head. We do not go along with that thinking.
If you over-torque the spark plug, you risk cracking it or destroying the spark plug, but it should not blow out of the cylinder.
How Can You Tell If You Have a Blown Spark Plug?
Some guides go on and on listing symptoms of a blown spark plug, but again, you don’t need to worry about diagnosing anything.
When your engine blows a spark plug out of the cylinder head, it will sound like a gun going off. We’re talking LOUD, noticeable, and anyone near the vehicle when it happens will notice.
Furthermore, when the engine is running, it’s going to sound awful if it’s going to run at all, and this is just for one blown spark plug.
When you look under the hood, if you see the spark plug hanging there by the wire, it’s not hard to diagnose.
How Do You Fix a Blown-Out Spark Plug?
If you have your vehicle, go to a professional shop to get it repaired; there is no telling what they will charge you. You will find, some shops will get you in and out for about $800, and others will try to bill you close to $4,000, and suggested that they replace the entire heads.
Since you can see how much of a range there is in repair costs, it is a good idea to know how to fix the problem to establish a baseline from which to work.
There is a standard repair kit to diagnose this problem, and it provides the items you need to fix the issue.
The kit provides a rethreading tap to rethread the blown-out spark plug hole, and then there is a sleeve that you install, and then put the new spark plug in.
Don’t just put the spark plug back, because you’ll likely blow it right out again. In addition, make sure you use the proper torque spec for the sleeve so you will not have this problem again.
How Much Will This Cost?
Most shops will charge you between $800 and $1,000 to fix an engine from a blown-out spark plug.
However, if you’re willing to do it on your own and buy the necessary repair kit to do the job, you can expect to spend anywhere from $250 to $600, or more, depending on the engine.
All of this price difference comes down to the cost of the tool you need. There are different tools for different engines, so there is no way to really cut any of that cost.
How to Prevent Spark Plug Blowout
You do not want the spark plug blowing out of the cylinder head, and the prevention method comes down to the proper torque specs on installation. Do not use the low end of the torque spec in the older Ford service manuals for your spark plugs.
Some guides will recommend you check the torque of spark plugs more frequently, but if you used the proper torque specs the first time, there is no way to catch the slight loosening of a spark plug in the cylinder head, and it is a waste of your money if you are paying a mechanic to do that, or your time if you are doing that yourself.
Also critical, if you’re wondering if you should put anti-seize or any other kind of lubricant on the spark plugs when you install them, absolutely not, you want to avoid doing this, as this can affect torque spec, and it is your only line of defense against a spark plug blowout.
Will Glow Plugs Blow Out on a Diesel?
While it is possible for a glow plug to blow out of a diesel engine, it is somewhat rare. Also, the most common reason for a glow plug getting blown out of a diesel engine is that the compression unit gets too high in the compression chamber.
That’s pretty much it for this one, but if you don’t torque down glow plugs properly when installing them, then they are as likely to blow out as a spark plug.
However, since there is no well-known issue of misinformation on glow plug torque specs, mechanics probably install them correctly the first time.