100,000 Mile Spark Plugs ???

[Christobal]

Old thread but timeless topic, I'm about to change some 100 K mile original the vehicle platinums. I've never not been able to get plugs out, but never changed plugs in that long, nor changed plugs in an aluminum headed street vehicle.

Anyone who's had trouble getting them out, short of putting enough torque on them to destroy threads or heads etc. as mentioned, pulling them out dead cold, what about spraying wd-40 or similar in there once twice, even three times and driving on it, to work it in the threads with heat? I'd try it once cold if I couldn't get them out without help....

What about this logic, if aluminum expands more than iron for a given temperature rise, shouldn't the plugs come out easier when hot since the everything on the block should be expanded or larger than when cold to a larger degree than the plug, when cold vs. at operating temp?

 

[EasyRhino]

Old thread but timeless topic, I'm about to change some 100 K mile original the vehicle platinums. I've never not been able to get plugs out, but never changed plugs in that long, nor changed plugs in an aluminum headed street vehicle.

Anyone who's had trouble getting them out, short of putting enough torque on them to destroy threads or heads etc. as mentioned, pulling them out dead cold, what about spraying wd-40 or similar in there once twice, even three times and driving on it, to work it in the threads with heat? I'd try it once cold if I couldn't get them out without help....

What about this logic, if aluminum expands more than iron for a given temperature rise, shouldn't the plugs come out easier when hot since the everything on the block should be expanded or larger than when cold to a larger degree than the plug, when cold vs. at operating temp?

First, don't use WD-40, use PB blaster - the best penetrating fluid out there.

Although your logic seems to make sense, the aluminum threads will be softer and more susceptible to damage when hot. Second, which has the highest temperature coefficient of expansion - the aluminum used in the heads or the steel used in the plugs? This is not the same 'math' as used to heat up fasteners to loosen them.

Do it cold.

 

[Khaelbee]

The average "off the factory line" explorer will NOT get 30 MPG even if you towed it or rolled it off a cliff. If someone is going to get 30 MPG on a stock EXP, they will have to modify it with great expense.

i beg to differ, last time i went out on a camping trip, i drafted a trailer the whole way there and got more than 30 mpg's... so it CAN be done.

 

[Christobal]

I would think the aluminum in the threads of the head as opposed to the similarly (read almost exact) shaped iron threads of the plug, but agree it's not that simple......

Just pulled a plug 03 4.0 and I'd say it took 30-40 pounds to get it to break away. Threads were a dry light brown, ground strap was clean and a lean looking light brown. I didn't measure but the gap looked Huge, definitely larger than the normal looking gap ~.040 or so out of the box Autolite platinums I purchased tonight for replacement. They were cheap, but other than the gap, the ground strap and electrode shape and overall condition looked outstanding. I am considering cleaning these up, regapping and reinstalling with anti-seize. A miss developed ~5-10 K ago. I changed the wires and seemed to get some improvement but not all the way. Now it seems the same. After looking at this gap and wondering how it got there with the GS and electrode looking so smooth and unpitted/eroded, I think I'll find the excessive average gap through the motor is the problem, if I don't find one bad plug (dirty,carboned,otherwise an oddball) I hope that's the problem.

More later. Almost feel like taking pics of the plugs after what I just saw.....


I like the sound of that 30 mpg drafting. The best I've seen in either the 93 or the 03 was ~25 in the 03 after replacing the thermostat and noticing it's running a bit warmer than it use to. It has 3.73 rear gear.

The 03 has 3.55s but doesn't seem to do as well. It's probably more efficient overall but IIRC it's heavier, larger aerodynamic profile, though it looks to have a better drag coefficient. Should be a wash I'd think. Maybe I'll do some testing.......behind trailer to AZ and otherwise. Once you get to Arizona from CA's 55 mph towing speed limit, seems like most of the rigs immediately bump it to 70-80 mph.