Diesel RVs: [diesel_mercedes] Re : Glow Plug Service

I'm lazy so I remove the injector pipes by slacking off all 10 17MM nuts .

Re - installing them can be tricky as you need to start each nut by hand but leave then loose until all 10 are 100 % started before tightening any else you'll surely cross thread them and begin a very bad week (or longer) indeed .

The towel stuffed in isn't difficult and really does help .

The last two glow plugs are close but will indeed come out once they're unscrewed ~ you just have to work at it .

This job is one that shows so clearly why it's important to keep your engine as clean and free of accumulated grease and oil as possible .

IIRC , The _OTHER_ Nate made his own glow plug thread reamer by filing slots on the threads of a bad glow plug .

Use _ONLY_ 6 pointed tools here ! .

Chicks dig scars or at least that's my story .

Opps ~ gotta run , Tom's here .

-Nate
Tom Wrote :
>
> For a few months, the old 300SD has been hard to start. Sometime around
> February, when I was rushing off to the east coast to put a parent in
> hospice care, the glow plug light on the dash stopped working. I prayed that it
> was only the bulb, and that the cold So. Cal. winter (nights dipping down
> into the low 40s) was the cause of long cranking in the morning.
>
> As February gave way to March, and the need to focus on some
> litigation matters and getting tax returns done, the cranking got longer, the starts
> harder, and the certainty of bad glow plugs more clear.
>
> Sometime in there, Nate came up with four glow plugs left over from a
> 240 project. They've been sitting, waiting for attention for 8 or 10 weeks
> now.
>
> This morning, fresh back from Commencement Week at Harvard (the old
> Dad finally got his degree, at age 91 1/2!! But he still couldn't change a
> spark plug in his own car), I found myself with no excuses. I either had to
> sit down and work on important writing, or go attack the glow plugs.
>
> Now, at 1:00 p.m. in the afternoon, I am here to tell you that the
> factory folks, and Nate, and all the paramedics and independent mechanics in
> the world are WRONG. It IS possible to change at least the first three glow
> plugs in a 617 engine without removing all the injector pipes and linkages
> around the left side of the engine.
>
> On the other hand, it is NOT possible to do so without major gouging
> of skin and blood loss.
>
> For those who care, the essential tools are 8 mm and 12 mm wrenches.
> God bless Craftsman, or whomever it was who invented the ratcheting box end
> wrench. It is possible (though it involves acts of faith and blind
> feeling around) to get wrenches on the glow plug ends.
>
> The 8mm works the nut that holds the glow plug wire. This nut is a
> special creation of German engineers, and has much higher gravity than normal
> 8mm nuts. Therefore, at any point one of these nuts is loose, its high
> gravity will pull it toward the ground. The path from the proper location to
> the ground involves a variety of blind spots, between the engine block,
> the injector pump, the ALDA unit, and other things, for the nuts to get
> wedged behind.
>
> Nate, with his decades of experience, has often expressed the thought
> that when working on areas of the engine where bits might fall into
> inconvenient spots, one should always start out by stuffing a shop towel down
> below where the bits and pieces might fall from, and above where they might
> fall to. If you contemplate this idea for just a moment, thinking about the
> left side of the 617 engine, you will quickly realize that with all the
> linkage and injection plumbing stuffing anything in there is completely
> impossible.
>
> However, I followed Nate's suggestion, and learned the actual
> scientific benefit of the towel. A terrycloth towel, stuffed into a small space,
> actually counteracts the increased gravity effect of the special German
> nuts. This effect means that once the towel is in place to catch them, the
> nuts lose their inclination to fall, and they stay wedged between your fingers
> as you contort your hand to withdraw it after taking the nut off the glow
> plug.
>
> Leaving the towel in place continues this effect when installing the
> new glow plugs, and reinstalling the nuts - they stay with your hand until
> the threads have caught and you can tighten them down.
>
> Some of you may have seen that Kent Bergsma, up in Bellingham, sells a
> glow plug hole "reamer". I did NOT buy such a thing.
>
> When I pulled each glow plug out, I was amazed that even when the plug
> was fully unthreaded, it didn't want to pull out of the hole. Then the
> new glow plugs were just as reluctant to go far enough in for the threads to
> catch. Some of the old glow plugs had a slight taper at the end. None of
> the new plugs had such a taper - they were rounded at the end, but with the
> same barrel size right to the end. These plugs did NOT want to go into
> the holes.
>
> They eventually did, and once they were in far enough for the threads
> to catch, they went right on in and tightened up. I expect that what they
> were encountering was schmutz build up around the old plugs that resisted
> the new ones. This is probably what Kent Bergsma's "reamer" cuts out.
>
> The center glow plug turned out to be the easiest one. There is NO
> space for getting your hands in to manipulate wrenches, although the plumbing
> makes it look more open. But a 1/4" drive, on a 6" or longer extension,
> reaches over the rear end of the injection pump and provides clean, not
> angled access to both the wore nut and the glow plug body. A deep 12mm socket
> works fine on the glow plug, coming out.
>
> To install the new glow plug with the deep socket, I had to drop a
> couple of nuts into the socket first, so that the glow plug didn't drop in so
> far that I couldn't get the first threads caught.
>
> It looks like the #4 and #5 glow plugs are going to be more work. The
> #4 will unscrew right into the side of the ALDA / shut off valve unit.
> And #5 will unscrew into the side of the oil filter housing. I have no idea
> how to catch the wire nuts for these two. At least the drop from these two
> looks like a cleaner shot to the ground. So maybe an old piece of carpet,
> with a little big of pile, underneath the car to keep a falling nut from
> bouncing a few blocks away.
>
> By the time I got the first three done, I was done myself. So the
> others will have to wait for another day.
>
> After getting the tools put away, I turned on the key. Then I
> remembered to go reconnect the ground lead on the battery. Then I turned the key
> again. The glow plug light on the dash was back. The engine lit off in
> about 1/2 turn.
>
> In a few days, I'll probably start to hear clanking noises letting me
> know where the forgotten tools are. But for now I'm wallowing in a sense
> of accomplishment. And typing while I wait for the paramedics to arrive and
> pack my scarred, scraped, bleeding, swollen knuckles in ice.
>
> Tom
>