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
