E300D glow plugs - WOW - that was easy!! - PeachParts Mercedes-Benz Forum

sokoloff · #1 02-02-2011, 06:17 PM

Had my #3 glow plug go out on me and attacked it yesterday and today. The last time I had to do glow plugs in this car, I had one break off and had to drill it out. I wasn't looking forward to doing the job again. I decided to try it with the car hot. Set my torque wrench to 40nm with the intention of seeing if that would be enough to loosen the plugs. I was doubtful that would be enough. But lo and behold the first glow plug loosened very easily at probably about 30nm. I couldn't believe it. Tightening torque was 27nm. I was so happy that I decided to see if the others would be just as easy to do and they were. However I couldn't count to six and for some reason never did the sixth glow plug. Forgot about it until several hours later. By that time the engine was cold of course and that last plug was significantly harder to loosen, but it did break free and come out. So I reamed the holes, cleaned up the old glow plugs, reapplied anti-seize which was still evident from the last time and reinstalled the glow plugs. I was debating on whether to get all new glow plugs, get one new one or just install a used one that I had in my spare parts box. Since they came out so easily after six years, I just put my spare used one in and will see how that goes. So whether it was the hot engine (most likely) or the anti-seize, I was really happy with the way things went.

WINGAS · #2 02-02-2011, 07:51 PM

Hot would make sense aas the alloy head would tend to loosen a freckle as opposed to the steel. I remember the last time, you had a near nitemare!

My #2 is pretty tight, and I'll have to try it again hot and replace it.

sokoloff · #3 02-03-2011, 11:55 AM

Gene - good memory - my last experience with the glow plugs was awful!!

Oldwolf · #4 02-03-2011, 12:19 PM

I always thought you were not supposed to work on hot aluminum heads. The threads are supposedly easier to strip hot than when cold. I guess not. How hot was your engine?

sokoloff · #5 02-04-2011, 12:18 PM

Quote:

Originally Posted by Oldwolf

I always thought you were not supposed to work on hot aluminum heads. The threads are supposedly easier to strip hot than when cold. I guess not. How hot was your engine?

The engine was hot from a one hour trip that I just returned from. So by the time I got the manifold off and was at the glow plugs it had cooled off only a few degrees I'm guessing. Fortunately there wasn't anything too hot in the areas where you had to work - very few third degree burns.

jim-sokoloff · #6 08-20-2011, 04:43 PM

Debated starting a new thread, but decided to tag onto the old one here. Had #1 glowplug fail on the wife's car and after being part of the tail end of my dad's nightmare original change, I wasn't looking forward to the possibility of the same, especially on a car we need everyday and having it down a few days while I futzed with it wasn't going to go over well.

#1 is the only one reachable without taking off the intake manifold, and I let the car idle for a few minute after a short trip while I got my tools out. By the time I was ready, the engine was definitely warm and I actually left it running while I broke the #1 GP free. (You can't loosen it much like that, so I just broke it free and then shut the engine off.) You can get at it with a 6-inch or longer extension. I used 1/4", but you could probably make a 3/8" work.

Proceeded to remove it, ream it, and install the new one. I chose not to use anti-seize as the one that came out didn't have any and came out very easily. Hopefully I don't regret that down the road.

Total time was right around half-hour, and fully a third of that was trying to determine if the MIL would go out just by starting the car a couple times. Seems it wasn't, so I cleared the code with my scanner and cleaned things up.

GregMN · #7 08-20-2011, 05:39 PM

Quote:

Originally Posted by jim-sokoloff

#1 is the only one reachable without taking off the intake manifold

#4 can be changed by only removing the crossover pipe.

Quote:

Originally Posted by jim-sokoloff

I chose not to use anti-seize as the one that came out didn't have any and came out very easily. Hopefully I don't regret that down the road.

You will. There is NO excuse for not using anti-seize.

TMAllison · #8 08-21-2011, 01:58 PM

Quote:

Originally Posted by GregMN

#4 can be changed by only removing the crossover pipe.

You will. There is NO excuse for not using anti-seize.

Turbo's don't ahve crossovers; only 95-97's do.

I've never used anti-sieze on mine; neither does the factory or dealer. Mine have been replaced once. CUrrent set has almost 200k on them.

babymog · #9 02-03-2011, 01:40 PM

If you're approaching the melting point of the aluminum alloy, the threads will be softer, but your head is destroyed. Anything in the normal operating range will not soften the threads measurably.

Hot is a good idea for 606 glowplugs since they sometimes are a bugger. The aluminum has a much higher thermal coefficient of expansion than does the steel glowplug, theoretically decreasing the annular pressure & friction.

ds190 · #10 08-21-2011, 10:06 PM

Quote:

Originally Posted by babymog

Hot is a good idea for 606 glowplugs since they sometimes are a bugger. The aluminum has a much higher thermal coefficient of expansion than does the steel glowplug, theoretically decreasing the annular pressure & friction.

My tiny brain does not understand. If warming metal expands it, then wouldn't that increase the friction between the metals (either aluminum or iron or both), and make it more difficult to remove the glowplug? I would think it a glowplig would come out the easiest after the car was left outside overnight in 30 degree temps.

1975300D · #11 08-22-2011, 01:23 AM

Quote:

Originally Posted by ds190

My tiny brain does not understand. If warming metal expands it, then wouldn't that increase the friction between the metals (either aluminum or iron or both), and make it more difficult to remove the glowplug? I would think it a glowplig would come out the easiest after the car was left outside overnight in 30 degree temps.

Yes, but what is expanding exactly? The hole gets larger as the metal expands. The plug doesn't get wider, it may get a micron longer, but not wider.

Think of furniture. When wooden furniture dries out it shrinks. If you have a peg in a hole when the furniture is damp, and then you let it dry out, does the peg get loose, or does it get tight? It gets tight as the hole shrinks.

vstech · #12 08-22-2011, 02:34 PM

Quote:

Originally Posted by ds190

My tiny brain does not understand. If warming metal expands it, then wouldn't that increase the friction between the metals (either aluminum or iron or both), and make it more difficult to remove the glowplug? I would think it a glowplig would come out the easiest after the car was left outside overnight in 30 degree temps.

Aluminum head expands faster and more than steel glow plug body does. so the aluminum hole gets larger than the Steel glow plug.

most materials have differing rates of expansion. aluminum is a fast expander to heat. steel is also... water *(in the form of ice) actually shrinks with heat... odd.