Pulling spark plugs on aluminum head

[Cressida]

I saw on another forum where someone said it's best to change spark plugs on a hot engine. I don't agree but didn't comment because I figured it must be some millennial

. Nevertheless, I wanted to see if something has changed in the last 30+ years...

1. For a engine with an aluminum cylinder head, isn't it still recommended to pull the plugs when the engine is COLD ?

2. Despite that recommendation, I believe it's best to do a compression test on a warm engine. Are most of you pulling your plugs when doing a compression test after the engine has been warmed up or doing the test on a cold engine?

I plan to do another compression test before winter so thought I'd ask (last time I forgot to hold the throttle open).

 

[dogememe]

I've only ever done it when the engine was cold. I don't like getting burned by hot car parts. Actually I'll admit I didn't wait that long on the Escape and the spark plugs were still warm, but not hot to the touch. So far so good!

 

[StevieC]

We have done them cold and hot. I don't think dealers or indie shops wait until the vehicle has completely cooled to do plugs. They do them and get them out the door.

The important thing is not to force anything and work a difficult plug back and forth until it gives.
Lots of penetrating fluid helps sometimes on those plugs that have been in their holes a long time.

It's less of an issue if factory torqued and not over tightened the last time the plugs were installed.

 

[mclasser]

There's a risk of pulling the threads on a hot engine. Most shops don't wait for the engine to cool down when doing a tuneup so it's probably a small risk. I don't want to test the odds so I've always waited for a stone cold engine.

 

[SnowDrifter]

Pulling plugs while hot is best for problem vehicles. Looking at you, Ford. All else, it's typically not an issue either way. Of note: Aluminum as a higher coefficient of expansion than the plug does.

 

[Trav]

Generally they should be removed cold but there are instances that hot works better (on a crush washer plug) like a badly sticking plug, on tapered seat plugs the heat can jam the plug even tighter against the taper so its probably not the best idea for these.
For this post I am referring to plugs using a washer.

Aluminum expands at a far greater rate than steel so that little extra clearance can make the difference.
The chances of the threads coming out with it are actually less than attempting to force a stuck plug out cold.

The main issue with hot aluminum engine heads is as the expansion of aluminum is much greater so is contraction,
When tightened the contraction can literally seize the plug making it very difficult to remove next time,
Use a small amount of never seize on the threats regardless if the plug is plated or not will go a long way in preventing seizure,

Only experience can tell you if you are dealing with an iffy situation with a sticking plug but generally if it wont budge cold start the engine for a few min and try again, penetrating fluids are of little benefit until the plug has moved slightly.

 

[SnowDrifter]

Originally Posted by mclasser
Most shops don't wait for the engine to cool down when doing a tuneup so it's probably a small risk.


Depends on where the plugs are located and if we can reasonably get to them without burning ourselves

 

[camrydriver111]

Anybody try running down spark plugs with an impact? I wonder what would happen.

 

[StevieC]

I will admit we have done this when doing by hand failed. It also failed and we ended up using a breaker bar and a piece of metal fence post on the end of it for enough torque.

 

[SnowDrifter]

Originally Posted by camrydriver111
Anybody try running down spark plugs with an impact? I wonder what would happen.

In? No. Out? Every time I can get the tool in there

 

[Lyman]

I always change them on a cold engine. I just did them on my Jeep and it was a breeze.

 

[cjcride]

Originally Posted by camrydriver111
Anybody try running down spark plugs with an impact? I wonder what would happen.

Don't give them ideas

 

[Trav]

Originally Posted by camrydriver111
Anybody try running down spark plugs with an impact? I wonder what would happen.


Running it down with a impact depends on the impact your using, if it was a small 1/4 driver with 18lb torque not much, a big 1/2 on full tilt its going to rip something apart in short order.

 

[53' Stude]

Trav: on my 2AZ-FE, I'm planning to do the plugs while cold. Is that a good idea? Thank you

 

[Trav]

Yes, that's the way I would do them. That uses a crush washer so if you did have a overly tight one (chances are you wont) you could warm the engine for a few min to help it.

 

[nthach]

I've done them cold and always by hand.

NGK and Denso say no anti-seize but I've always put on a bit of C5-A on the new ones.

 

[53' Stude]

Originally Posted by Trav
Yes, that's the way I would do them. That uses a crush washer so if you did have a overly tight one (chances are you wont) you could warm the engine for a few min to help it.



Thank You Trav for your A1 professional advice

 

[spasm3]

I do AL heads cold, if they move but feel tight, I work them back and forth until I get them out.

 

[maxdustington]

Originally Posted by SnowDrifter
Pulling plugs while hot is best for problem vehicles. Looking at you, Ford. All else, it's typically not an issue either way. Of note: Aluminum as a higher coefficient of expansion than the plug does.
The only time I have seen it recommended on this board is on the 3V. Yikes!

 

[Trav]

Originally Posted by nthach
I've done them cold and always by hand.

NGK and Denso say no anti-seize but I've always put on a bit of C5-A on the new ones.


I would love to drag the little [censored] that wrote that up here and force him to get their plated plug out of the Subaru I did a few years ago.