spark plug broken
 

1986 mercedes 300e
I have broken the spark plug off leaving the thread body of the plug in the cylinder.
I have had these plugs out many a time but since the shop put new leads on the plugs are extremely tight.
Any suggestions on how to get the rest of the plug out?
Thanks.

Take it to the shop.

They put it in too tight, let them get it out.

Tom W

Thanks Tom.
Problem is they claim they never removed the plugs. My reply was if they were troublshooting the ignition and servicing the engine why didn't they check the plugs???

Can't wait to hear how this turns out....Good Luck!

Easy out
 

I snapped a spark plug in my 88 300zx a few years back. After my heart started beating again, I called a mechanic buddy and he said to get an easy out and stick the 3/8" square drive end into a suitable socket (electrical tape helped to ensure a snug fit. Attach a socket extension. Then, tap the "chiseled" end into the remains of the broken spark plug until it bites, then slowly and careful use a breaker bar or rachet to break it loose. It worked like a charm!!! After that fiasco, I used dialectric grease every time I repaced plugs. Good luck!

p.s. I believe the easy out size I used was a 6t-4

EZ out size may vary by manf. I use a #9. Get the innards out of the broken off plug before using an ez out.

Just wondering if it be better to remove with engine cold or hot? Would spraying wd40 help?

Rule of thumb on an aluminum head is to change plugs when cold.
After you get the threaded portion out, crank the engine over a few times, to blow out any debris that may fall into the cylinder. ;)

There may be a valid reason for installing plugs in a cold engine, I think removing them from a warm or hot engine is easier. Certainly a dealer ship tech is not going to wait for an engine to cool.

Wow. Thanks for all the input. I have sourced out the ez out tools and will be applying all the suggestions this afternoon.
Let you know what I learn today.

Good luck. Take care that you locate and account for the side electrode(s) that may snap off and drop into the cylinder. A piece of wire with a blob of grease on the end works well for fishing them and other swarf out of the cylinder.

PSark Plugs
 

:eek:NEVER NEVER EVER REMOVE ON A HOT ENGINE. :eek:

You most likely have an aluminium head which expandes with heat and will vise up on the plug. If you think a broken plug is bad try bringing the plug out only to find that it brought the head threads with it. You should never remove any bolt from a hot aluminum block or head. It be very bad.:eek:

While I'm thinking about it.
 

Apply some petroleum jelly to the surface of the spark plug you are going to drill and tap out. The PJ will catch the small shavings and keep them from falling into the cylinder when you back the plug out. Drill the hole slow and it will keep the chips bigger and easier to clean out. Also make sure that you don't drill completely throught the plug as it will blow out the back end and all that stuff falls into the cylinder and is near impossible to get out unless you crack open the head to get in there. EZ outs are great but be carefull you don't go frying pan to the fire.

The hole for the spark increases in size when hot. I have no idea where you got the information it decreases, but it's wrong.

No need to drill a broken spark plug- I never have.

Every machine shop guy and tech I have ever talked to including my father who has 35 years experience as a mechanic. Heat up some aluminum and tell me if it doesn't expand. Since it expands (swells) it will constrict inside a hole.

It depends on how bad a condition the plug is in and what kind of removal tool you are using. The ones I use that allow more torque use a small pilot hole. I have had the best results with those.

Once the hex of the plug snaps off the only thing remaining is the thread. The hole thru the threaded part is quite large already. Use anything smaller than the proper size ez out and it will likely drop into the cylinder.

I have more than 35 years experience and aluminum does expand when heated. Aluminum housing are heated when bearings are pressed in or out. Sometimes a manufacturer specifies heating the head to remove or install valve guides. Your information is incorrect.

* Chas H is correct. With heat, the aluminum hole will present a slightly looser fit, not a tighter fit. That's why you apply heat (torch) around a threaded hole to work a seized stud/bolt out of it.
* The problem with replacing plugs in a hot alloy head is more of a caution than a problem. It's more likely to damage cyl head threads with overtorqueing when the threads are hot. Overtorqueing is still a problem cold but the threads are less likely to damage.
* Needless to say, the best way to tighten plugs is with a torque wrench. And the most accurate torque wrench scale in this case would be an inch-pound scale (where 18 ft-lbs would, for example, be 216 inch-lbs).
* But if you don't own an in-lb, or even ft-lb, torque wrench, work with a cold engine, put a drop or two motor oil on the plug threads and tighten the plug until you feel the crush-ring (if the plug has one) collapse. If the plug just has a tapered seat (and no crush ring), and you don't have a torque wrench, you'll just have to approximate it and tighten it until it feels gas-tight. Unfortunately, leaving a plug too loose causes a another, different set of problems.

My bad. I must have been misunderstanding what folks were telling me:(

Don't beat yourself up over this. ;)
For many years, Vehicle Manufacturers were very adamant about changing plugs on aluminum heads when they're cold.
I believe part of the problem is, if there is any amount of combustion residue ( hard carbon ) on the end of the threads of the plug, you have a tendency to pull the threads out of the head.
A warm/hot engine ( softer threads ) increases this risk.
" Heli -Coil " time.;)
To each his own. ;)

spark plug broken
 

Hey guys.
I got the spark plug out with a #6 ez-out.
The advantage I had was the plug sheared off just below the nut, so the whole core and electrode came out in one piece. No need to drill.
I treated the "thread body" with penetrating fluid, tapped the ez-out lightly with a hammer to get it to bite and then gently used a 1/2 inch drive breaker bar to crack it loose.
Worked slick.
Went from a $1400 head removal estimate down to $8.95 and some hair loss. Whew!
Again thanks to all who offered their help.
C'

I'm glad it worked out well!