Probably a search will bring up more than you ever wanted to know. Basically you disconnect the glow plug wire connector at the relay which is on the driver's side fender. Then stick the positive lead into each terminal while grounding the other lead. Good plugs will read about 0.6 or 0.7 ohms. If you look closely, each of those terminals is numbered, so will know which plug is bad if you get a bad reading. I'd be curious to know if you have any bad plugs since you have no check engine light or glow plug light staying on all the time. One bad plug on mine caused both the glow plug light and the check engine light to come on and the OBD code confirmed the bad glow plug as did my own ohm readings.

__________________
Len
'59 220S Cabriolet-SOLD and living happily in Malta
'83 240D 351,500 miles original owner-SOLD
'88 560SL 41,000 miles - totaled and parted out
https://sites.google.com/site/mercedesstuff/home
'99 E300 turbo 227,500 miles
'03 SLK320 40,000 miles - gave to my daughter
'14 Smart electric coupe 28,500 miles
'14 Smart electric cabriolet 28,500 miles
'15 Smart electric coupe 28,000 miles

I just replace mine a couple of weeks ago. I used Bosch Duratherm GP's. What was in there were also Bosch. One thing that concerns me is that after I did this I looked on the Bosch website and they have a cautionary statement about how to tell if they are a genuine Bosch GP. I bought mine online from a place I got off one of the MB Forums. I'm just hoping this supplier is buying genuine products and not a knock off.

just did the glow plugs on my 96 e300d, and the mercedes shop manual makes no mention of using anti -seize on the glow plugs. I did some further checking, and came up with a couple of sites indicating that the use of the wrong anti seize compound could cause problems. This was just one of them. Just wondering about opinions regarding this matter. Thanks.....



http://mbca.cartama.net/archive/index.php/t-2066.html

I would. After 2 years my plugs came out nice and easy with anti-seize. Before that, they were tight. 3 were stuck. 2 of them came out eventually and one broke off. Yes, we had to take the head off. Machine shop found the prechambers were pretty clean and not carboned up

__________________
01 Ford Excursion Powerstroke
99 E300 Turbodiesel
91 Vette with 383 motor
05 Polaris Sportsman 800 EFI
06 Polaris Sportsman 500 EFI
03 SeaDoo GTX SC Red
03 SeaDoo GTX SC Yellow
04 Tailgator 21 ft Toy Hauler
11 Harley Davidson 883 SuperLow

Just a thought; I recently lost my voltage regulator. The initial symtom was hard/rough starting. Simply a weakening battery will cause the GP's not to reach the proper temperatures. The GP sequence seems to terminate on time not temperature. Air in the fuel lines will also cause the exact same hard/rough starting. The colder ambient temperature causes my o-rings to shrink and suck air. I have replaced the o-rings in the past but it appears I must replace them again. (or i missed one...)

__________________
85 300sd 400k
99 e300td 101k (hers)
34' californian twin 5.9 cummins
1999 F350 Powerjoke 75k
2001 F150 Supercrew 51k
19681/2 GT/CS

First, thank you for all of the support. GP #3 was bad and I only replaced that GP. All of the other GP's test at 0.9 resistance. I have removed the intake so many times on this 606 that I almost can do it blind folded (GP replacement, o-ring replacement, fuel line replacement, muffler grease pack replacement). The longest time of the procedure was dropping the 5mm wrench to unmount the intake from the tube from the intercooler. I drove to a store to buy a another 5mm wrench because I could not find the one I dropped in the engine. But as life is when I got back I found the #$%@ wrench. Four hours total. If I did not drop the !$#%! wrench it would have been under three hours. By comparison I can replace GP's on a 617 in 35 minutes. The 606 in my 210 is fun to show off to others what a diesel can do, but I love my 617's

As a rule, I would replace only one if I had a few miles. For instance, if one burnt out 10K after I installed a new batch, I would replace that one. Otherwise, if it is long enough, I replace them all. If I elect not to do it, I would certainly R&R the plug and dab some anti-seize on the threads so it doesn't freeze up. After all, I paid admission when I bought that intake manifold crush gasket.

__________________
01 Ford Excursion Powerstroke
99 E300 Turbodiesel
91 Vette with 383 motor
05 Polaris Sportsman 800 EFI
06 Polaris Sportsman 500 EFI
03 SeaDoo GTX SC Red
03 SeaDoo GTX SC Yellow
04 Tailgator 21 ft Toy Hauler
11 Harley Davidson 883 SuperLow

Personally I feel the risk of breaking one off is too high to remove GPs that still work. FWIW I would have done exactly what Nate did - replace the bad one and move on. This has been debated ad-nauseum in the past but it bears repeating here. There are two theories on what causes the plugs to stick. One is the threads seize and one is the carbon built up around the tip. Using anti-seize should remove the threads from being an issue, so if you install a set using it then there is no reason to R&R them just to test it and make sure it isn't stuck if you believe the threads are the cause of sticking.

I happen to believe the carbon build-up is the bigger threat to sticking, so, in that case all of the anti-seize in the world won't stop it from sticking. It's up to fate then. Why roll the dice to make a problem if the GP in there works and might continue to work for years more?

Since I can now R&R the IM in under an hour I'm of the opinion that GPs should be changed like light bulbs in a fixture...as they burn out. When I bought my car I did replace all 6 as PM because I didn't know if or when they had last been changed but in hindsight I was lucky that they all came out relatively easily and anti-seize was used on the new ones at that time. Risking breaking one off just to see if they will come out seems to me to be unnecessary, as is replacing ones that still work since they can last for years more, although I do understand that position's rationale, I just don't agree with it.

__________________
Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

nhdoc,
I'll throw another idea at it. It's somewhat middle of the road on both accounts. I think if your doing your own work replace just the ones that are bad. If you have it done for you, replace them all. It's the difference of about $400.00. But keep in mind, A shop's theory on things is if it was broken while removing you pay. If it breaks going in, they pay.
Mike

__________________
1999 E300 Turbodiesel
179,000 Miles

Hi Mike,

I'm not sure I understand your theory here...I'd bet there is not a shop or dealership that would absorb the cost of pulling the head or drilling out a broken GP if one broke during removal...if you know of one let me know and I will gladly have them replace all of mine the next time one fails. The fact is, if they break one while trying to extract it you'd get the call that it happened and you'd be on the hook for all of the cost of extracting it. That plus the fact that a shop is much more likely to rush the job and break one off where a little patience would get it out intact would make me never bring mine in for all 6 GPs.

__________________
Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Each time you do, it is $10 for the copper gasket. The reason I do move everyone is so that I can take it out and put fresh anti-seize on it.

__________________
01 Ford Excursion Powerstroke
99 E300 Turbodiesel
91 Vette with 383 motor
05 Polaris Sportsman 800 EFI
06 Polaris Sportsman 500 EFI
03 SeaDoo GTX SC Red
03 SeaDoo GTX SC Yellow
04 Tailgator 21 ft Toy Hauler
11 Harley Davidson 883 SuperLow

nhdoc,
I had to go back and re-read my post. I am saying the same thing as you. A shop will not pay if they break a GP while extracting it from the engine. They will pay if they break one while putting in the new one.
I asked this question to my indy (friend).
Thanks,
Mike

__________________
1999 E300 Turbodiesel
179,000 Miles

Nate - I'm curious. When I had one bad glow plug, my '99 threw a check engine light and glow plug light. You say yours did not. What was the reading on that bad glow plug? I'm wondering why mine did and yours didn't?

__________________
Len
'59 220S Cabriolet-SOLD and living happily in Malta
'83 240D 351,500 miles original owner-SOLD
'88 560SL 41,000 miles - totaled and parted out
https://sites.google.com/site/mercedesstuff/home
'99 E300 turbo 227,500 miles
'03 SLK320 40,000 miles - gave to my daughter
'14 Smart electric coupe 28,500 miles
'14 Smart electric cabriolet 28,500 miles
'15 Smart electric coupe 28,000 miles

Mine did that too. GP light comes on then goes off, start it, check engine and GP light come on.

__________________
01 Ford Excursion Powerstroke
99 E300 Turbodiesel
91 Vette with 383 motor
05 Polaris Sportsman 800 EFI
06 Polaris Sportsman 500 EFI
03 SeaDoo GTX SC Red
03 SeaDoo GTX SC Yellow
04 Tailgator 21 ft Toy Hauler
11 Harley Davidson 883 SuperLow

When I first changed the glow plugs two years ago (all six) the CHECK ENGINE and GP light were both on. I did not check the resistance at that time which I now wish I would have for comparison. This time there was one bad GP, but no CHECK ENGINE or GP light. The resistance on the bad GP was 0 or at least as displayed on the tester.
Since I replaced the GP's with Bosch after market GP's I wonder if there is some subtle difference in the OEM vs. after market that might affect the electrical systems monitoring of the GP's which could make the difference as to whether or not the HECK ENGINE and GP lights are triggered.