stuck glow plug on 617 - PeachParts Mercedes-Benz Forum

VW1300 · #1 10-09-2007, 10:41 PM

I recently diagnosed a weak #4 glow plug on my '85 300D. I doused it in liquid wrench earlier this evening, but all attempts to remove it with a regular wrench have failed. My 12 mm socket is too shallow to get solidly on the hex head. A deep 12 mm socket is too long to fit between the plug and IP body. I will continue to spray it down every day or so in hopes that it will eventually penetrate.

I read over some old posts regarding this problem - apparently it doesn't happen often in the 617 engine. Usually, others who have had this problem shear off the head or strip the threads, and end up drilling it out somehow. I don't even see how I could get a drill in the proper position to drill this plug out.

Are there any other techniques/tools I can try to get this out without resorting to destruction of the plug? I don't have the time right now to deal with drilling etc., and I may have to take it to a local MB specialist if I can't get it out intact. I'd hate to do that - my pride will be hurt - but I'd really like my startups to be as easy as they used to be.

thanks,

TheDon · #2 10-09-2007, 10:47 PM

wax....

heat up some wax and pour it onto the body.. the wax will seep in and aid in the removal..

its something like that.

Did you do it on a cold engine? doing it on a hot engine would probably help as well

#3 10-09-2007, 10:50 PM

Drive the car really hard. Getting the engine hot will soften the carbon and make everything expand.

VW1300 · #4 10-09-2007, 11:17 PM

Engine was cold. Getting it good and hot sounds worth a try.

TheDon · #5 10-09-2007, 11:23 PM

I did my glow plugs on a semi hot engine.. came out easy squeezey

removing the injector hard lines is also a good idea. try not to burn your self .. mechanics gloves are a plus

sailor15015 · #6 10-09-2007, 11:35 PM

I always try to do my gp changes while killing time to allow all the oil to drain during a change, like I did this afternoon. I drove the car for about twenty minutes to get the engine nice and hot, both for the oil change and for easier removal of the gp's. My #1 gp, the bad one, came right out with no problem. Of course, I've already changed all the plugs on this car (the '84) at least once so they all had a nice coating of anti-seize on them, which you would do well to do on any plugs you replace. Chances are you won't have to pull the head on the engine but rest assured that if you do, its really not a bad job at all and can be done by someone who has never pulled a head before in less than a day. Get a wrench that has a ratcheting box end. Better yet, two; one for the gp nut and the other for the gp itself. This makes removal so much easier, as does removing the hard lines, also not a bad job.

pimpernell · #7 10-10-2007, 11:55 AM

I have been reading a lot of the "stuck glow plug" posts, and one of them had an idea that made some sense to me. He recommended that you bring your engine up to operating temperature, and then take a canister of air "the type sold in camera and computer stores", turn it upside down, and depress the contents onto the stuck glow plug. His theory is that the exiting canister propellant will bring down the temperature of the glow plug, thereby causing it to contract. For about $4.00 a can, it is worth a shot. Good luck!!

Brian Carlton · #8 10-10-2007, 12:06 PM

Quote:

Originally Posted by pimpernell

I have been reading a lot of the "stuck glow plug" posts, and one of them had an idea that made some sense to me. He recommended that you bring your engine up to operating temperature, and then take a canister of air "the type sold in camera and computer stores", turn it upside down, and depress the contents onto the stuck glow plug. His theory is that the exiting canister propellant will bring down the temperature of the glow plug, thereby causing it to contract. For about $4.00 a can, it is worth a shot. Good luck!!

You'd be far more successful with a chunk of dry ice pressed directly onto the glow plug...........wearing suitable gloves, of course.

dieseldan44 · #9 10-10-2007, 12:09 PM

I am reading that so far you have only tried socket wrenches. Give a BOX end wrench a shot, or better yet, a gear wrench. These worked very well for me to get a solid grip on the glow plugs with clearance.

Remove the solid injector lines that are in the way will also help.

***corrected open to box end wrench
dd

Brian Carlton · #10 10-10-2007, 12:15 PM

Quote:

Originally Posted by dieseldan44

Give an open end wrench a shot.........

Don't.

That's a recipe for failure. Use a box wrench or a gearwrench, as you noted.

vstech · #11 10-10-2007, 02:55 PM

gear wrench makes some pass through sockets called gearratchets. I love the 1/4" size set. they are 6point sockets my set comes with metric and sae for 10.00, it comes with an extension and such... great for pulling the GP's
http://www.tylertool.com/gearwrench38.html wow, they are up to 30.00? hmm I would shop around for a better price.

TMAllison · #12 10-10-2007, 03:30 PM

If using a shallow 3/8 drive socket that wont reach the bolt head try a 1/2" drive socket. It will be longer.

Worse case is cut your deep socket down to the length that "will" clear your IP.

VW1300 · #13 10-10-2007, 03:40 PM

Thanks...that gear ratchet set looks like exactly what I need...I'll look around for better price, although $30 doesn't seem THAT bad for a slick little tool set, if it is decently well-made. I think it will work well for brake bleeder nuts too, which have traditionally been a problem for me.

By the way, I did try an open-end wrench first - I'm no master mechanic but I have learned the hard way not to use too much force with it...

VW1300 · #14 10-27-2007, 10:22 PM

FOLLOW UP: I tried the gearratchet to no avail. The engine was nice and hot. The plug is really in there. Seeing as I have 4 other good glow plugs and I live where it rarely freezes, I'm not going to worry about it for now. I have some other home projects that need to be completed...thanks to all for their ideas, I may come back to this at a later time.

pawoSD · #15 10-27-2007, 10:47 PM

Engine hot + spraying the canned air propellant or brake cleaner on the glowplug should work to rapidly cool the plug. I've had good success using this method on a bunch of different bolts etc....