Replacing old spark plugs which might be stuck

I’ve changed plenty of spark plugs without issue, but have never had a vehicle which made me cautious about trying to remove them…until now. I bought my 96 Caravan with 150k, now at 156k. No idea when (if) plugs were ever changed, therefore it’s due by definition. But in an old thread I found comments by @VDCDriver and @thesamemountainbike mentioning difficulty in removing plugs which have been in a long time. Uh oh.

So then what?

Based on those comments, I have not yet tried to remove the plugs, seeking advice first. Remember of course that accessing the back 3 plugs is a major PITA starting in 1996, much worse than on previous 3.3L Caravans which are merely hard to reach. Aside from blowing compressed air into the plug wells first to clear away any debris, is there anything I can do to reduce the chance that I’ll have a problem getting those old plugs out? How likely is it that I really will have a problem?

Is a penetrating spray like PB Blaster of any value? Would it help to have the engine hot? That could be a complication for pulling those back three plugs because reaching them requires squeezing hands against lots of hot metal.

It’s worth noting that this engine did not run for at least 4 years, possibly 5 or 6, before I rescued it. I’m guessing that might have increased the chance of trouble getting the plugs out. BTW, the engine runs fine, though mileage may be declining a bit (planning on a new O2 sensor next week).
Any thoughts? Thanks!

– Roadtripper

Would it help to have the engine hot?

NO…You want a COLD engine. Metal expands when hot. And if this engine has aluminum heads then you run the risk of stripping the threads.

Let the PB blaster sit over night to soak in. Then try it.

Worse case scenario is you’ll have to helicoil the spark plug holes.

I agree with @MikeInNH. Blow out the spark plug sockets and let PBlaster sit overnight. Work them out slowly, and reverse the ratchet to release tension if the plugs feel like they are binding. If they come out smoothly, cool. If not, use a dab of anti-sieze on the threads of the new plugs to lubricate them. If they bind up and will not work free, plan on a heli-coil. Use grease in the flutes of the tapping tool to catch the shavings.

Good luck.

Thanks. What I’m most concerned about is those inaccessible plugs in back. The plugs are barely visible from underneath. Factory manual gives some ideas on removing things on top. Just removing the connectors is tricky, not to mention turning the plug with good sensitivity for what’s happening. So a problem with one plug back there would equal major complications. That’s why I’ve postponed this job, I’m thinking of farming it out to a pro as “insurance.”

Anyone able to speculate on just how likely I am to have a problem, or is that very very rare? And the fact that the engine sat unused for so long - does that increase the chance of a problem removing a plug, or is it irrelevant?

I would remove them with the engine hot, not cold, because aluminum expands when hot. However, I would soak them in PB Blaster or SeaFoam overnight first, or even better, if there is a gun shop nearby, use BreakFree gun oil. It is the best penetrating oil you can get.

Heres the deal, the front plugs will be a guide to how hard the back plugs will be. If the fronts come out easily, then the rears should also. Another trick that might help is to get a rope and tie it somewhere near the back of the engine and then pull it forward and tie it off to the front of the van. You might use a 2x4 to help rock the engine forward, then tie it off. There should be enough play in the motor mounts to allow the engine to move about an inch or so and any extra room to get at those back plugs will help.

If you have motor mounts under the engine attached to the cross member, you can remove the rear motor mount to help get it to rock forward further. Just be sure to have a safety rope attached to the engine before removing the rear mount or the engine will rock in the wrong direction.

Follow the recommendation in the manual for warm or cold. There is only one way specified for that particular engine. I’m guessing warm. My work is done here and everywhere else for that matter.

I have replaced the spark plugs on a couple of dozen Caravans. On the '96-2000 3.3L and 3.8L I replaced the rear bank from under the vehicle, it takes about 15 minutes. If your laying on a creeper you may not be able to reach the plugs very well. The engine should be cool, you’ll be resting your arm on the exhaust manifold.

If you choose to replace them from above removing the wiper plenum takes about 15 minutes and will help some.

Replace the spark plug wires at the same time.

After loosening the spark plugs a half a turn you should be able to unscrew them with your fingers. The only time thatI found spark plug difficult to remove on a Chrysler product is when the last installer didn’t tighten the plug enough and the threads filled with carbon. A shot of carb. cleaner softens the carbon quickly.

Thanks @Nevada_545, I appreciate the voice of experience. I’ll take another look from underneath. The factory manual is cryptic but advises working from above. It says to remove the alternator (they call it “generator”) for #1. For #3 and #5, they say to remove the resonator and intake strut. After looking again just now, removing the wiper plenum looks like a better option than what the manual describes.

Sir, I would recommend that u r on the right track with blowing out the debris and spraying with PB blaster, Given that this engine has aluminum heads I would attempt spark plug removal in the follwing manner: with the engine cold, I would tighten the removal of this spark plug barely 1/16th of an inch, then I would very carefully back off the removal of this spark plug approximately 2/16th of an inch taking careful mental note of the feel of backing out the spark plug 2/16th of an inch and spraying the PB Blaster penetrant down to the base of the spark plug (s) in question. I would then recommend letting this rust penetrant soak overnight and attempt to remove said spark plug the next day (sic) continue removing said spark plug (s) very slowly and carefully again with mental feel of any resistance to the removal of said plug, if continued resistance is felt spray more penetrant and let sit again overnight. Continue removal of spark plug again the next day, carefully, carefully and slowly. Make sure when u install new plugs, please make sure that u coat the threads with an anti- seizing compound. Sir, this should work.

I appreciate your advice, thank you. The catch is that with the rear plugs so difficult to access, it’s going to take some ingenuity simply to direct the PB Blaster spray to the places where it’s needed. I’ll get it, but the job won’t be easy. I’m visualizing a small funnel and a some clear tubing…and probably removing that wiper plenum.

If you take off the wiper plenum, it will be much easier to access the rear plugs. It’s not difficult to remove, and it’s well worth the effort.

Update: When I said “wiper plenum”, I really meant “wiper tray”. The intake plenum (going into the engine) does not need to be removed.

I have removed a lot of plugs from these engines and they are not easy to get at with my large hands but I have never seen one threatening to seize up.

I would like to add one thing to all the great advice here. If the plugs feel like they are turning hard or getting stiffer, change direction thread them back in a turn or two and then continue to remove them. If they feel like they are starting to bind reverse as many times as needed. Sometimes a little finesse is better than brute force.

@TheBeaglesHaveLanded - thanks!
Just today I began thinking of your suggestion - turning slightly in the opposite direction. Two months ago I applied that to a stubborn old hose bib I needed to replace. So I’ll nudge it CW first, then give it a bit more force CCW, just to start judging what I’m dealing with, and if necessary continue as you suggest, applying PB Blaster and elapsed time as needed.

I also agree with this:

"Sometimes a little finesse is better than brute force"
...and not just with regard to car repair!

@oldtimer 11
I was relieved to see your comment that you’ve had no problem with seized plugs, as was mentioned previously here. I have small hands and good dexterity, which will work to my advantage.

I have a 2000 Caravan 3.3. Mine was changed at 75K miles, I did the front and took it to pepboys for the rears ($100 well spent). Now I checked one of the fronts at 155K miles and the gap is wide and the plug base is burnt, so probably time to change again. Looking up and down the net, you can either go from bellow or above. Number one is the worst. From above the wiper tray has to be removed, most remove the plenum (I would rather not do this part). The alternator bracket has to be removed for number one. I doubt the plugs are frozen in place, they are just difficult to get to.

“I would remove them with the engine hot, not cold, because aluminum expands when hot.”

The metal expands in all directions. Foe a hole, this means the hole decreases in size because the aluminum expands into it.

Thanks jt.
I should have known that.

“hole decreases in size because the aluminum expands into it”

Uh, I think not. When the metal is heated, the hole expands – just like the metal. (I saw the proof of this in high school physics: the hole is just the place where you took out the metal; if the metal had expanded, the hole will expand.) From real-life experience, many times I’ve heated metal tubing (aluminum) to make its i.d. expand to let a thinner tube fit into it.

I agree with Art. Any hole gets bigger when an object is heated. The issue here is whether the plug expands more. While I think aluminum expands more than aluminum for a given temp change, the plug could easily be hotter.

Remove the three front ones…If they come out normally, then you can expect the rear three to come out the same way…Put some anti-seize compound on the threads of the new plugs…