glow plug installation - PeachParts Mercedes-Benz Forum

#1 12-03-2002, 08:24 AM

Doe anyone know if I should use a thread joint compound of any sort when installing my glow plugs?

Ken300D · #2 12-03-2002, 08:31 AM

Two things to suggest for a glow plug replacement:

1) Glow plug reamer. A fairly expensive tool, but it cleans out the carbon deposits around the glow plugs - making them easier to install and more efficient in operation.

2) A small amount of Anti-Seize on the threads when you install them.

Ken300D

franklyspeaking · #3 12-03-2002, 12:20 PM

I changed my glow plugs Saturday evening....a couple of them didn't want to come out, because of the carbon deposits. I did not have a reemer, and so I just installed the new ones. Will this carbon buildup affect the life of the plugs? I changed them last November, and so they only lasted a year. At least one had stopped working, because the relay light would not come on and it was hard to start in the mornings. The reemer costs $46.20 at Performance Products - is it worth it?

Stevo · #4 12-03-2002, 12:34 PM

Seems they should last longer than a year. What kind did you buy?

gsxr · #5 12-03-2002, 02:29 PM

I'd pass on the $46 reamer. I've heard you can take an old plug, hammer the end flat, and use it as a reamer. Crank the engine over a few times with all the plugs out to "blow out" the carbon pieces, if any. If you have serious carbon buildup, you should pull the prechambers and bead blast them or something... then they'll be REALLY clean!

Oh, and if you have carbon in the first place, you're not driving the car hard enough. You need to do at least one or two full-throttle redline runs with each tank of fuel to keep things cleaned out.

franklyspeaking · #6 12-03-2002, 02:35 PM

Last year I bought Champions. This year I bought Autolite. I realize that forum members seem to swear by Bosch, but I would have to order them or drive 30 miles to the Mercedes Dealer. Perhaps the short life I am getting is related to the domestic brands and has nothing to do with carbon buildup???

I could see an argument that the carbon may be insulating the plug, which would lead to overheating it and burning it out prematurely. I should have marked the two plugs that were the tightest to see if they were the ones that failed.

Ken300D · #7 12-03-2002, 02:47 PM

Hi Chris - I saw your PM about the tap.

No, the reamer is a bit different from a thread tap, because the reaming part is a little larger than the glow plug itself, but not the size of the glow plug threads.

If you do use a reamer, it makes the new glow plugs go in without any restrictions from the carbon buildup. I could tell there was carbon in there because the old GPs wouldn't come out without a lot of careful twisting and shaking. After reaming all the cylinders, I turned over the engine to clear out the carbon - whoosh! Black cloud of soot!

You'd have to think not having carbon packed all around the glow plug would make it work more efficiently - its purpose after all is to get red hot and ignite air/fuel mixture.

My Bosch glow plugs have all come from the FastLane on-line parts sales right here - see FastLane button above.

I don't know if Bosch glow plugs are date coded, but the ones that came out had a number on them that might indicate 1986 or 1996. If 1986 then they would have been the original glow plugs. If 1996 that's still not a bad service life.

Ken300D

#8 12-03-2002, 06:14 PM

Thanks everyone for a lot of very useful info. Does anyone know the diameter of the reamer part of this tool? I have access to a machine shop, so maybe I can make something. Thanks again, CJ.

rickjordan · #9 12-03-2002, 09:28 PM

Instead of buying a reamer, try a 6mm allen wrench. Anything that has hard edges to it and that fits should work. I never thought to crank the engine over, without glowplugs to blow the carbon out. I'll have to try that when ever it comes time to change my plugs out.

Ducati · #10 12-04-2002, 04:58 PM

Let me get this straight - Its actually OK to drive the crap out of a diesel, right? (once the engine reaches proper operating temperature) I have been feeling guilty that I have been abusing my old girl (Car, that is...) with my daily full throttle 100+ mph blasts down Hwy 99.

ck42 · #11 12-04-2002, 05:32 PM

Ducati,

From what I've heard/learned from others WAAAY more knowledgable than me concerning diesels, you are doing your motor a favor by driving it that way.

Apparently, the worst thing you can do is drive it like a granny.

In case you hadn't heard of it, the Italian Tune Up involves repeated high RPM runs to 'clean out' the motor. By driving it hard, you're basiclly doing this on a daily basis.

Besides, MBZ designed these motors to be driven hard and fast on autobauns(sp?).

Chris
'85 300SD

#12 12-04-2002, 05:32 PM

franklyspeaking

I bought Autolite last year . Then a month later took them all back to NAPA and they gave me Champions.
Those failed less than 5000 miles later.
So I bought Bosch. So far, so good. Bought them at a local MB shop I found in the meantime. He said Bosch is the only way to go. He was not at all enthused about Beru. Said would do no better than the Autolite and Champions.
Can't say the Bosch are better yet. Will let you know if they make through the season though.

dabenz · #13 12-04-2002, 06:16 PM

Cleaning and greasing the reamer before each hole means you won't have to puff as much. The grease picks up some of the carbon before it drops into the pre-chamber.

#14 12-04-2002, 11:03 PM

I'm hearing two conflicting schools of thought on this subject. The first is to ream the carbon out of the glow plug holes, turn over the motor, and blow out the soot. The second I'm hearing from a diesel mechanic is don't ream, because there's the possiblity that you could knock some carbon chips into the cylinder, causing them , maybe, to get stuck in the exhaust valve. Maybe a shopvac could come in handy while the reaming is taking place. Any thought's?

leathermang · #15 12-04-2002, 11:17 PM

"If you have serious carbon buildup, you should pull the prechambers and bead blast them or something..." GSXR

Finally someone other than me mentions the precombustion chambers.... this seems to be a verboten topic ... when my reading of the manual and the drawing indicates that if carbon is a problem out on the working end of the glowplug that it is certainly causing a problem with the spray pattern from the injectors... Those are very small holes ( 7? ) in the precombustion chamber bottom... and any carbon built up or dropped into there needs to be cleaned out...

Why is this such a NON TOPIC ? The cost of the tools to get them out ? Just afraid to go that deep into the engine ? Talk to me !