123 glow plug replacement tip and story
 

Hello all,

When I first got the car, I posted all sorts of questions.
Thank you for your help and responses.

Now I will post something other than a question.

1) Autozone had the glowplug, and they were 11 or $12 each Bosch

2) Installing them (all 5) solved the hard starting, hands down!

They were kind of difficult to put in, but I was able to manage with my (not large) hands, a craftsman socket set (including the deep ones), a 1/2 wrench, and a magnetic pick-up tool. I only had to remove 1 piece of throtle linkage and a small vacuum hose to get to the last one. The coolant hose, I was able to push it out of the way, and up on top of the oil filter housing.

THE TIP - Magnetic Pick-Up Tool, and how I used it.

These are very cheap and handy. They look like a small radio antenna with a magnet on the end.

When unscrewing the little 8mm nuts, get the magnet there to catch them, esp. if you dont have a good grip with your hand. ALSO when putting them back on, If you can squeeze your hand down into possition, do it without the nut in hand. Then PASS THE NUT TO YOURSELF with the pick up tool.

Thanks for all the advice about not dropping them. I did this and it worked!

Happy Dieseling

Mark
Running WVO blends.

Mark,

I always loosened the GP nut and then removed the GP with the nut and wire still on the GP. Then I removed the nut and wire after the GP was screwed out of the head. I then installed the wire and nut on the GP first before starting the GP in the head and tighte dthe GP nut after the GP was screwed tight in the head.

But now that I have ratchet box wrenches, I have to remove the GP nut first. So for GP installation, I cut the wire connector into a "spade lug" so I can put the nut on the GP first and slip on the connector after the GP is tight in the head. This is because the ratchet box wrench can't be used if the wire is on the GP.

The above was on a 116 engine. I haven't done any GP work on my 603 engine yet. Not really looking forward to it.

P E H

Jim,

How about the other 4 GP in the 603 engine? Seems like others on the forum advise that the intake manifold must be removed.

I should probably remove the manifold and crossover pipe anyway to see how much crud is in them.

I didn't understand what you meant by "the nuts are captive on the wire end".

P E H

Some of us did get that....... :D :D

Jim,

I'll have to go out to the SDL and see how the captive GP nut and connector work. I still think a new GP should come with a new nut on it unless the nut is not removable from the connector.

As you probably know, I'm a big proponent of the "not broke, don't fix" philosophy. Especially with GP. GP are kind of like a light bulb, they either work or they don't.

Seems like U were lucky that the GP that "broke" were ones you could get at to R&R. I probably won't be as lucky.

P E H

I'm well aware of your philosophy. :D

But, just so everybody else is not steered in the wrong direction, a glow plug is not like a light bulb. The heat produced by the glow plug is directly dependent on its resistance. As the plug gets older, its resistance climbs and the heat output is reduced accordingly. A glow plug with a resistance of 1.2 ohms, which I am sure you would continue to use, draws 33% less current and puts out 33% less heat than a glow plug with a resistance of .8 ohms.

No big deal if the temperatures are above freezing, but, when it gets cold................ :mad:

BTW, What is the thread size for 123 glow plugs ? -thanks

glow access
 

my (big) hands never were able to do this with out taking all the fuel lines off. the one next to the firewall is the exception. i got so i could do it in about a half hour.

Brian,

You are correct that a GP that increased its resistance would draw less current and would not get as hot.

However, I have never seen a GP that changed much in resistance before they burned out completely. And remember you are measuring cold resistance which is not always a good indicator of the hot resistance which can only be measured by measuring the hot current and the voltage applied.

The best GP test is to connect them directly to a good 12v car battery and observe how hot they get. If they don't glow a bright orange, they should probably be replaced. I would do the visual hot test on any GP that measured over 1 ohm cold.

P E H

Jim H,

I agree with every thing you wrote. Light bulbs get dimmer because some of the tungsten filament boils off (that's the dark coating on the inside of the glass) and the filament resistance gets higher. Thus the current gets lower and the filement is a little cooler and gives less light.

I'm not sure GP get higher resistance as they age. All mine seem to have about the same resistance: 0.6 +/- 0.2 ohms. I would be suspicious of readings that were exactly the same as yours are. Did you pull the GP cable connector out of the GP relay when you measured the GP resistance? Since I measure the GP resistance thru the connector's female terminals, I may have read some difference because of the resistance of the wires and the connection to the GP terminals.

I will have to try reading GP resistance at the GP with the cable connector in the GP relay to see if there is any difference.

But all the GP that I found bad were completely "dead" I.E. open circuit equivalant to a burned out light bulb.

P E H

I view a light bulb as more of a device where the current is constant. Although I can't say that I ever checked one, IMHO, the current when the bulb is brand new is within 5% of the current on the day before the filament blows. There is not a lot of material to degrade and allow the resistance to climb. The bulb fails before this can happen to any great degree. Personally, I have not noticed a drop in lumens as the bulb ages. Have you?

Those are the cold readings. I'm not overly concerned with the absolute reading because, as you have mentioned, various ammeters will read different values at such a low range. If you have glow plugs that have been on the vehicle for awhile and they read 1.2 ohms, and you compare this to a brand new plug and get a reading of 1.2 ohms, you make a good case for no degradation of the plug with extended use. If this situation can be considered generic, then I agree with PEH and the plug functions in similar manner to a light bulb.

However, this would be in direct contrast to those folks who have changed to a brand new set of glow plugs and have benefitted significantly via easier starts. Naturally, if such folks had an open glow plug in the pulled set, this would cause the data to be discarded immediately.

So, the question remains, as far as I am concerned. If the plugs function in similar manner to a light bulb then there is no reason to check resistance values. Either the plug is open or closed.

However, I remain skeptical. ;)

8 mm nuts
 

If Bosch had a speck of humanity instead of Teutonic correctness they would put a $.02 nut on each new glow plug & it wouldn't matter if we dropped one ( which I did & had to go to a Honda motorcycle dealership & beg one). Spark plugs come with new top nuts (yes, those things come off, & should be tightened with pliers before installing), shock absorbers come with new top nuts (maybe not Bilstein -- I don't know yet) .........

I'm still learning about my new (to me) 240D. This morning at 45 deg. it didn't want to start. When I first got it it smoked (fuel) on start up and then I diesel purged it and now am adding redline 85 plus. It doesn't smoke much now. It also starts fine when temp is 60 or better outside. I'm thinking it is a glow plug issue. However can I eliminate valve clearances since it starts OK warm ? I checked the resistance of the glow plugs and none are infinity but they vary a lot. Does that mean I should go ahead and replace them ?

DeltaDave,

First check the valve clearances. It there is little or no valve clearance, this could be the cause of your cold starting problem. Then adjust the valves, they probably should be adjusted anyway.

As far as the GP are concerned, remove one and connect it across the battery terminals and observe if the GP glows a bright orange. If it does, that GP is OK. Do other the GP the same way.

To connect the GP to the battery, hold the GP in a Vise Grip. Touch the end of the Vise Grip to one batteryterminal and use a screwdriver to connect the GP terminal to the other battery terminal. Be careful of handling the GP, if they are OK, they will get hot from the above test.

P E H

On my 603 the #2 was easy as well, about 15 minutes. I was prepared with my magnet for the nut to fall off but it didn't. Took me a while to realize that it was captive. Very nice warm feeling of appreciation to the german engineer who thought of that for these engines. BTW, no way will my hands fit next to the GPs. I just used a long set of needle nose pliers and some deep sockets, extensions and a wobble wrapped in tape (for less wobble).

cheers,
Matt.