Last fall we bought a 98 C class motorhome on an E-450, V-10 chassis. I drove it home ( about 40 mi ) and stuck it in the yard. That is all the history I have on the unit. I have since spent the Winter visiting sites where there is much wailing and tearing of hair learning that all my spark plugs will blow out, in sequence, one at a time, just as the memory of the last one is starting to fade. This rig, as stated, is coming on 11 years old but has only a little over 50,000 miles on it and still runs fine.

My questions:
Should the plugs be left alone or retorqued?
If retorqued then just retorqued or backed off a little and retorqued or pulled ,cleaned and reinstalled or pulled and replaced?
Should retorquing be a regular maintenace item?
Anti sieze or dry?
(Last one) Would a one minute cool down idle like you do for a turbo help stop the plugs from working loose and ease the strain on exhaust studs as well?

 

MY opinion:

You are FAR more likely to never experience a problem. Chickens who perceive falling skies are VERY, VERY loud. And annoying.

That said, it does occaisionally happen.
My theory (I am a mechanical engineer, so not pulling it out of my tush):
I firmly believe the vast majority of blown plugs are the result of improper torquing. The average gorilla working on a Ford is used to screwing steel plugs into cast iron heads, where you can get away with just about anything. So torque wrench is an unknow term or item.

These are aluminum heads, and as with ALL aluminum heads, torque is quite critical. Let some gorilla overtorque them even ONCE, and the aluminum is overstressed and compromised and will eventually fail. Undertorque them, and they will come loose, rattle around, and destroy threads.

At 50K, the plugs have probably never been replaced, so odds are way, way, way in your favor.

Two options:
1) If you will only have RV for a couple years: Remove the COP's, and check to make sure the plugs are not loose. Get a 3/8" drive beam style torque wrench ($20) and just gradually apply tightening torque. If you reach 20 lb-ft and nothing moves, stop and call it good. I would advise against removing and retorquing. If good, leave them be. Why risk inducing damage?

2) Go ahead and change plugs. If you plan to keep RV for a long time, I would strongly recommend this option. Steel plugs will fuse with aluminum head if left undisturbed for extended periods. Changing now breaks any fusion that has started.

My recommendation based on my research, heavily filtered with my experiences and engineering theories is as follows. There are many theories, specs, recommendations, and wives tales regarding this, so be prepared to hear contrary suggestions as well. Use your own judgement.

- Use new Motorcraft SP-479 plugs.
- Install dry.
- Torque to 20-25 lb-ft.
- After 500 miles, pull COP's and check if still tight (gradually apply 20 lb-ft).
- Change every 5 years.

On the Last question, I would say no. I believe it is more a factor of the total swing in temperatures rather than the rate of change.

 

I have to agree with mwsF250. Mostly.

If you're going to just drive it for a couple of years, leave it alone, and MAYBE check the torque on all the plugs. Make sure you use dialectric grease when you put the boots/COPS back on and call it good.

However, I suspect once you're in there, you are going to find a lot of rust on the end of at least one or two of the boots.

If the plugs are original, they are not zinc-plated (galvanized), being from 1998.

If it were me, and I was going to keep the vehicle for a long time to come, I'd change the plugs, being VERY careful to use penetrating oil (not WD40) and letting it sit on there before even THINKING of loosening the plugs, and then only about 1/8th turn before spraying more penetrating oil in there and letting it sit another couple of days. Then slowly back them out, and if you meet ANY resistance, more penetrating oil, working the plug back and forth until it gets nice and easy.

Then, after all the plugs are out, use an inspection mirror to check the condition of the threads. If any threads come out with the plugs, or the threads in the head don't look consistent, I'd seriously think about putting inserts in it.

I would NOT, however, torque up the plugs as far as 20-25ft/lbs. The '98's and basically all V10's built previous to late 2002 use only 3-4 threads and you're asking for a problem.

I would, however, install plugs (with anti-seize), torque to 14ft/lbs, install the COPs and run it up to operating temp a few times, and then go back and re-torque all the plugs. You can just let it idle for a 1/2 hour with a few to-the-floor go-pedal applications, and let it cool all the way down, then heat it back up again for a total of at least 2 or 3 complete heat-and-cool cycles. Then re-torque to 14ft/lbs.

 

You agree more than you think! Anti-sieze (which is superb thread lubricant) at 14 lb-ft actually applies about the same or possibly even more shear force to the threads as dry at 20-25 lbs.

I debated with myself about the usage of anti-sieze for quite a while. I normally use it just about every time I screw a steel fastener into aluminum

This is one of the few exceptions. Having the plug dry should reduce risk of loosening, which is one of the fears. Since the new Motorcraft plugs (as I understand it) already come with a nickel plating, that should reduce the electrolytic seizing. But I;m not completely comfortable with it, hence the 5 year max to change plugs.

Your recommendations on removing the old ones are excellent.

 

I look at anti-seize as a sort of loc-tite in a way. The zinc galls and keeps the darn thing where it's supposed to be.

Anyway...

 

Good advice above! Take it...and welcome to FTE!!

 

I really appreciate all the advice, gents. It's looking like a plug change. After all these years it may take some amount of patience and profanity to get them out without costing a lot of money. I haven't even had the dog house off so I don't know what kind of access issues I will be looking at but it can't be a lot worse than the '84 GM van I replaced with this one.
I still have to wait until it's warmer and more of the motorhome is sticking out of the snow. I' ll let you know how it comes out.
(Hope I don't end up doing a Time-Sert commercial)

 

With an E-series and the dog-house off, it's very easy to get to the back of the engine. The problem will be the front ones, namely 1/2 and 6/7. Maybe removing the passenger-side seat would be a good idea.

(can you tell I've worked on E-series engines before? )

 

Greetings, forum newbie but original owner of my 99 F250 (V10) with 53K miles. Couple of things-

This formum is awesome! I've had the pc in front of me for hours, reviewing all the great stuff here.

I am in maintenance mode with all my toys and had already decided to change the truck's plugs. So I scanned the forum looking for the obvious things, special tools, plug# anything I needed to know up front. Which was my first exposure to all this hell about the earlier heads and blowing plugs. So 1st (WAAAAA freak out) Shame on Ford! Ok Im over the initial spazz.

Read many threads on the subject; this particular one is excellent. MY MAIN QUESTION-

Does it make more sense to change the plugs when the engine is hot or cold, and why? (A cool engine is easier on me but I am strictly thinking about what's best for the procedure given everything I have read...)

I sure appreciate your comments, thanks!

 

Great advice above from knowledgeable, reliable sources. I did not Anti-sieze mine only because the Ford Tech told me not to but I have heard alot of info leaning either way. Good luck to you.

 

(Bump.)

I reviewed more threads and came across one mentioning a TSB and a warm engine before removing plugs. What I reviewed mentioned this was to reduce carbon on the plugs before removal.) I brought it up thinking perhaps the spark plug thhead holes expanded a miniscule amount when they're hot; probably not.

The expanded method Krewat outlined made a lot of sense with a caveat-

Using some aerosol based chemical spray (e.g. carb cleaner) to remove any penetrating oil that would remain on the threads after the old plugs are removed, before applying new ones. It seems to me not doing so may cause issues down the road and I am not certain how it would react with anti sieze (which I agree with and will use.) If nothing else wouldn't leftover penetrating oil skew torque readings when the new plugs are installed? Perhaps this is not important. After the initial panic wore off I am glad to find this forum and to be able to use the advice to plan the right course of action to (hopefully) avoid any ordeal.

Thanks again!