Replacing Spark Plugs

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Denso Spark Plugs
Denso Spark Plugs

Replacing spark plugs has always been a favorite task of do-it-yourself auto mechanics. The interesting thing about this maintenance operation is that on some vehicles it is fun and easy.

On other automobiles the task is extremely difficult and sometimes the path of success is plagued with extreme problems that could lead to pulling the cylinder head.

Sometimes when spark plugs are removed from a cylinder head the threads will have traces of metal on them.

Each spark plug removed should be numbered with the cylinder it was removed from and inspected thoroughly for this type of thread damage. This type of car problem happens more often on engines that use aluminum cylinder heads.

If you run into this problem when performing your own sparkplug maintenance it is highly recommended to correct the condition before reinstalling the plugs. Patience and care at this point can save you from major auto repairs down the road.

Bosch Spark Plugs
Bosch Spark Plugs

If you force the plug back into the bore, or they become tight before they bottom the likelihood that the plug will leak or blow out increases.

If compression forces the plug out of the hole while the engine is running, a large amount of damage can occur to the cylinder head.

If this happens to you note that the head should be removed and checked for damage by a machine shop.

The end result may include and require replacement. It is also safe to say when this happens it will scare the hell out of the driver when it blows out.

Replacing spark plug tips

The number one rule for me is to never try replacing spark plugs when the engine is hot. If you remove them on a hot cylinder head The threaded holes can become egg shaped as the cylinder head cools without the sparkplugs to hold or retain the shape.

The number 2 rule for me is that replacing spark plugs should only be done when recommended by the manufacturer or if a plug happens to fail which is very rare.

Just a few years ago plug maintenance was recommended about every 30,000 miles. Now modern platinum plugs can go as far as 100,000 miles before maintenance is recommended (check your owners manual for recommendations).

Spark plug thread chaser
Spark plug thread chaser

When installing sparkplugs if the plugs cannot be installed easily by hand the threads in the cylinder head may need to be cleaned with a thread-chasing tap.

There are special taps for spark plug holes simply called spark plug chasers. You have to be really careful not to cross thread the new plugs when you’re working with aluminum cylinder heads.

It is also recommended that do-it-yourself car mechanics tighten the plugs with a torque wrench using the correct spark plug socket with out a universal joint if possible.

The following affiliate link will take you to amazons website were you can get special spark plug tools like thread chasers, wire boot pullers, replacement thread installers, torque wrenches and of course inexpensive replacement spark plugs.

Always follow the vehicle manufacturer specifications in your auto service manual.

Recap of the #1 rule: In most cases, automotive manufacturers agree with me that this car maintenance operation should never take place on even a warm engine. Let the engine cool down to the ambient surrounding temperature before you begin your spark plug replacement.


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7 Replies to “Replacing Spark Plugs”

  1. Charlie Diaz

    Dear Sir:
    I don’t feel my hands no more after do my best to remove My Spark Plugs from My Camaro V-8 1992
    is almost imposible to remove the plugs.
    I need your help is any special tool for get this SP out???.
    I thank you in advance for your fast response to this matter.
    Sincerely.
    Charlie

  2. Mark

    Charlie: I feel for you because I have done this task my self a few times on your model and year camaro. It’s just plain hard. And each plug has a different technique to get to it. Some are easier from the bottom reaching up ( having a vehicle on a lift is nice). The hardest one I remember is around the steering shaft and exhaust manifold. On that one I slide my spark plug socket on (that has a hex base) and use a straight flat wrench to back it out.

    They make several different types of spark plug sockets but none specially for the camaro that I know of. Nothing really makes it much easier. But you can protect your hands with tight fitting gloves. That will at least make it less painful!

  3. Charlie

    Dear Mark: I gave up the Sparkplug change in My Camaro RS V-8 , so I took the car to a professional Mechanic and he did it just Right . Now I have an another question Mark .

    To change the headers in this Camaro is it hard? My Camaro has an A/C, i just want to replace the old one for a new ones obviously I will put a new Cat . My Mayor dilemma is if I need to lift the engine to remove the old headers?
    I thank you deeply for your great help.
    Sincerely. Charlie

  4. Mark

    Charlie: Replacing the exhaust manifolds and upgrading to headers is a big job on a V8 Camaro. Depending on the brand and shape of the replacement headers (but in most cases) you do have to raise the engine. Also note (just my opinion) the stock exhaust manifolds have a pretty good flow rate. You don’t really gain much as far as horsepower. Again depending on the brand and the configuration of the exhaust you put behind them (maybe 10-20 hp increase.

  5. Charlie Diaz

    Dear Mark :

    Here i am, now i need to ask you how can I change the gas filter of my Camaro V-8 , I found the filter and looks old very remember My Camaro is 1992, But is loosing fuel power delivery, and when I am Driving the RPM star going low feels like the car is going to shout down. I bought New gas filter in PepBoys, but I was reading in My camaro book the I need to unplug the fuel Line from the Carburetor, is more easy if, I just unplug the old filter and put the new one?.
    I will Do this the engine of car Cold , unscrew the gas tank lid, disconnect the battery positive cable and hand on te Job.
    Mr >Mark just tell me if right my Thinking for work This.
    I thank you so much for your HELP and glad you are My Friend.
    Sincerely.
    Charlie D.

  6. chris S

    what if i accidentally didn’t follow rule # 1. I had a misfire, swapped plugs and coils and the misfire is more apparent now in the same cylinder. I wouldn’t say the engine was hot…but it was warm. Plug slid right in fine… but now the misfire occurs right when I start the engine. Did i make an egg shape and ruin the head?

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