Replace plugs or not

nissan
maxima

#1

My 96 Maxima has 58,000 on it and never had the plugs changed. I’m afraid of seizure to them, don’t miss or anything so should I change them?


#2

I’d change them just based on the time they’ve been in. That said, any seizing that’s going to happen, already has. Remove them carefully. I’d even squirt a small bit of penetrating oil right where the plug and head come together. Don’t pour it on, just a little. Let sit overnight and try to break them loose.


#3

I wouldn’t replace them.

But what you might want to do is see if they loosen up. And if they do, tighten them back up and drive on.

Tester


#4

What does your owner’s manual or maintenance schedule say about replacing the plugs? If it’s not due, and the car is running well, I would wait until it’s called for.


#5

I’ve found that using a little PB Blaster or other penetrating oil while the engine is still warm, and let it soak in for an hour. Then restart the engine for about 2 minutes, shut the engine off and then try to remove the plugs while they are warm…not hot. If the engine is too hot to work on let it cool some.

As far as “should I replace them”!!! That is where the owners manual is handy. Though I never leave plug in as long as the owners manual says.

Yosemite


#6

Your vehicle came equipped with platinum spark plugs. Platinum plugs normally have a 60,000 mile lifespan.

Assuming the car is running fine, if it were me, the decision to change them would depend on how long I planned to keep the car. If I wanted to keep it for another 20,000 or more miles, then I’d change them. If wanted to get rid of it over the next few years, then I’d be tempted to leave them be.


#7

https://www.carid.com/articles/types-of-spark-plugs.html

Tester


#8

You were smart to ask, but I don’t think you need worry that they’ll seize.
These spark plugs use flat bases with metal crush washers at the base, and do not protrude into the combustion chamber. Plugs that seize tend to be the ones with conical shoulders, particularly those plugs in Ford engines that protrude into the combustion chambers and get combustion-induced buildup on the lead threads, occasionally causing them to be virtually impossible to remove.

In short, while your fears are certainly not unfounded, the Maxima engine is very minimal risk for this operation.

While platinum tipped plugs generally are good for 60,000 miles, a 21 year old engine with 58,000 miles suggests a possibility of a life of short in-town trips or city driving. 58,000 miles of stop and go driving can be the equivalent of 158,000 highway miles… or more. I’d recommend having them changed.

If you desire to do the job yourself, I’d recommend an inexpensive torque wrench. Typical installation values for aluminum heads are in the range of 16ft-lbs to 24ft-lbs, and it’s awfully easy for a novice to exceed that and strip the threads out. When installing, be sure the plug spins in readily by hand; be sure the treads are properly engaged, before continuing with a wrench of any kind.

If you have trouble getting the first thread on a particular plug started, a “back tap” thread repair tool (see link) will straighten out the threads easily. The tool’s trifurcated end is inserted into the hole and the cone on the center shaft is drawn into the tool’s cavity with an allen wrench. It expands the thread to the proper size to reform the lead thread in the hole. The tool is then backed out of the hole. The tool is cheap (about $26) and a real lifesaver when needed. See the Powerbuilt website for details.


#9

Thanks for the info, it was very helpful.:+1:


#10

I’d be surprised if there were any designs today that had exposed threads in the combustion chamber. This is because that was a well known reason for emissions issues due to the increased crevice volume caused by the protrusion of the plug.

Modern plugs still can seize in the head for a couple of reasons. The primary one is galvanic corrosion. The plug body is steel and the head is aluminum. These dissimilar metals will corrode just from being in contact with each other. The spark plug manufacturer electroplates the steel to reduce the potential for galvanic corrosion but it’s not impervious. Some things people do that compromise the plating- over torquing the plug and applying anti-seize to a plated plug. The latter can affect the dielectric qualities of the interface and actually lead to corrosion between the two opposing metals. Antiseize is essentially grease and metal particles like copper, zinc, aluminum…The addition of these metal particles separated by grease actually helps the galvanic process and will erode away at the noble side- the plug body.

Then there is simply torquing them too much in the first place. This stretches the threads and may even end up galling the aluminum.


#11

Mountain Bike – That tool is so cool that I wish I needed one.


#12

Thanks. Most people, including many mechanics, don’t even know they exist.
Like any tap, they can also be purchased as entire sets. Every mechanic should have a set IMHO.


#13

I would remove one plug and check the color and tip. If it looks good check the gap and if that is within the tolerance just reinstall the plug and drive on, dude. If the plugs are very dirty or the tip is eaten away I would replace all plugs.