Another Glow Plug Broken - PeachParts Mercedes-Benz Forum

NewBEclass · #1 12-23-2004, 07:34 PM

I've read a lot of the posts for the broken glow plug problem. #3 in my car broke off after too high of twist. The center section of the plug is still sticking out, but the nut just spun right off. My friend and I would like to start drilling, but the injector unit (top large dia dish shape) is in the way. We have moved the lines and can't get a strait shot at the plug. Any Ideas would be helpfull.

Thanks, Newbeclass now oldbeclass

606 motor
95 E class D
240,000 miles
Grand Rapids, Michigan

aklim · #2 12-23-2004, 07:56 PM

E300TD glow plug stuck/broken

sokoloff · #3 12-23-2004, 09:17 PM

Well, after what I went through, I'd say that it WILL come out IF you can get a straight shot at it with a drill. Mine was #1, but I thought that it would be able to reasonably get to all of them except maybe #6. But I've never had to do #3, so I'm not positive about that. Any chance that a right angle drill would work? Heck, even if you've got to buy a new drill, you'll still be way ahead of having to take it to someone to remove the head to the tune of $2500!! Plus you'll have a new tool.

I'd get more aggressive with the drilling much sooner the next time I've got to do it, but I sure hope there isn't a next time.

Get all the threads removed from the glow plug that attach it to the head before you start drilling. Be careful not to nick the threads in the head. After the plug comes out (and it will - think positive), run a tap over the head threads to clean up any nicks you might have caused. I've got the tap size somewhere if you need it.

Len
'99 E300TD 72,000 miles

aklim · #4 12-23-2004, 09:22 PM

Quote:

Originally Posted by sokoloff

Well, after what I went through, I'd say that it WILL come out IF you can get a straight shot at it with a drill. Mine was #1, but I thought that it would be able to reasonably get to all of them except maybe #6. But I've never had to do #3, so I'm not positive about that. Any chance that a right angle drill would work? Heck, even if you've got to buy a new drill, you'll still be way ahead of having to take it to someone to remove the head to the tune of $2500!! Plus you'll have a new tool.

I'd get more aggressive with the drilling much sooner the next time I've got to do it, but I sure hope there isn't a next time.

Get all the threads removed from the glow plug that attach it to the head before you start drilling. Be careful not to nick the threads in the head. After the plug comes out (and it will - think positive), run a tap over the head threads to clean up any nicks you might have caused. I've got the tap size somewhere if you need it.

Len
'99 E300TD 72,000 miles

Let us know what size it is so we can skip the jumping around. TIA

sokoloff · #5 12-23-2004, 09:30 PM

M12 x 1.25. It's in the post that "akim" refers to above. The drill bit sizes are there too.

Len

kip Foss · #6 12-24-2004, 04:31 PM

I am an industrial maintenance mechanic on the Gulf Coast and often have fasteners that are nearly welded in place because of rust. Before I start twisting on them I soak them in penetrating oil and start tapping them with a hammer. By tapping I mean hitting them hard enough so that the hammer bounces off but not hard enough to peen them over. Hit on them for 5 minutes or so while you spray them with penetrating oil. It is a long 5 minutes but it can make the difference. The shock will usually fracture the rust in the threads allowing the oil to creep in.

If the fastener breaks loose, it is not guarenteed that it will but this is as good a start as you can get, don't try to loosen it all the way at once. Rock it back and forth while spraying it. If you try to take it out all at once you can gall the threads and then you are back to square one, except now you really have to drill the plug out plus you may have ruined the threads to the point that you need a Heli-coil.

Brian Carlton · #7 12-24-2004, 05:20 PM

Quote:

Originally Posted by kip Foss

Before I start twisting on them I soak them in penetrating oil and start tapping them with a hammer. By tapping I mean hitting them hard enough so that the hammer bounces off but not hard enough to peen them over.

The issue is not with the threads. It is the fact that carbon gets packed around the shaft of the plug and refuses to let it turn.

I agree with the approach to providing impact. However, tapping with a hammer might take 24 hours to get a result in this case.

I would like to see someone get an impact wrench, calibrate it at reduced air pressure so that it cannot put out more than 40 ft.-lbs. torque.

Set the wrench up on the glow plug and let it hammer away for an hour if necessary. The vibration created in the plug will, hopefully, break loose the carbon that is gripping the plug and allow it to slowly rotate.

If you keep the torque down below 40 ft.-lbs., it will not be possible for you to get agressive with a standard wrench and break the plug. Just set the impact wrench on the plug and let it hammer away for awhile.

dc88168 · #8 12-24-2004, 08:00 PM

I would suggest try do it when the engine is warmed up pretty good.

David
________________
1985 300D Turbo

NewBEclass · #9 12-30-2004, 06:09 PM

What a ride to get this glow plug out. It was a success, and the car is back and running great. This post is to incourage anyone that a broken glow plug is not the end of the world. With patience, the plug came out, and the car went back together without and extra or missing bolts.

Suggestions helped from everyone, but here are some more.

-pb blaster was a plus to get the plug out. I let it soak overnight.
-a reverse hammer was the last thing I needed.
-I tapped a 7mm bolt from a Yamaha dealer (thank the Japaneese for this)
-A reamer and at 12 mm X 1.25 tap is a must.

I hope this post helps, and thanks again everyone for the help.

sokoloff · #10 12-30-2004, 06:29 PM

Help me understand what you did NewBEclass. Did you tap the barrel of the glow plug and thread the 7mm bolt in and then use a slide hammer on it? Is that what popped it free? I considered a slide hammer, but didn't have one and couldn't find one in any of my usual parts stores on a Saturday. The PB Blaster didn't do me any good. I did use the tap however. Glad it worked out for you. So now we know that #1 and #3 can come out if they get broken off. I kind of think #2, #4 and #5 will come out too, but I'm not sure about access to #6. Anyone out there done any of the others successfully?

Len
'99 E300TD 72,000 miles

NewBEclass · #11 01-01-2005, 03:18 PM

yes, I called the tool incorrectly. It is a slide hammer. You explained what I did to a "T". I don't know about #6. You need a strait shot at the plug when you drill. If you don't you could wreck the treads. I had to take off the washer unit and something off the top of the injector unit to get a straight shot. I hope this helps.

TL

aklim · #12 01-03-2005, 06:08 PM

If you don't have an accurate shot or don't feel lucky, take the head off and go to a machine shop. See my saga E300TD glow plug stuck/broken

whunter · #13 01-04-2012, 12:09 AM

for the great picture in post #11.

.

connerm · #14 01-04-2012, 01:52 PM

Don't run a tap in the glow plug holes. Use a thread chaser. Big difference. Tap removes metal. Thread chaser cleans out and striaghtens out threads (if they aren't too fouled up). Because those gp tips get stuck, you need all the metal on the threads to be there.