It says that the new Bosh glow plug kit includes a new relay that will have the glow plugs stay on for three minutes after the engine has started.My question is will the life of these glow plugs be reduced if they stay on for so long? And is the only advantage to have this (new) system stop the engine from smoking?
Regards
Dan

I have one in my 300D, and it probably does shorten the GP life somewhat. I usually have to change one every six moths or so. Fortunately, you can change 617 GPs in your sleep. In addition to reducing smoke, the engine does run quite a bit smoother when it's cold. I think it's a significant improvement.

I agree with Craig about the mentioned improvements. I've had the new afterglow relay in my 240D for about 2 years now and so far I haven't had to replace any glow plugs. But then again, this car only sees about 4000 miles a year, if that.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

I drive mine about 35K miles per year, so maybe replacing a couple of GPs per year is normal. But, it does seem to go through a few more GPs with the new relay.

I did the glow plug kit conversion from loop to pencil style on my daughter's 240D a couple years ago and have yet to replace a glow plug. Definetly improved cold starts.

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85 300CD
83 300TD
78 240D (daughter)

Easier starting. also, cheaper to buy the kit than buy the four glow plugs and relay alone.

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Der Panzermann und Fraulein Fahrvergnuegen

1991 420SEL 201K "The Big Blue One"
1985 300DT 205K chassis/285K engine nee California emissions "Goldbug"
1983 300TDT 255K "The Womble"
1983 300 DT 214K "Sea Sprite"-Rear-ended a truck
1983 300SD 285K "The Donor" Gave his life so that others can live
1980 500SL Euro 105K "Der Panzer"

It makes sense that the GP would have a much shorter life.

Normal time the GP are on is maybe 1/3 minute. If they are on for 3 minutes after starting, they would be red hot for 9 times as long. This would definately reduce the life of the GP.

P E H

But when you say a "much shorter life," it is still in absolute terms a long time. I would presume that, like a lightbulb, most of the stress on a glowplug comes at the time you "turn it on." that's when most lightbulbs go out and likely when most glow plugs finally give up the ghost. Thus, it is the number of activations that is the primary determinant of lifetime. A glowplug that stays on 9 times as long may have the one staying on only 1/3 of a minute, but the lifetime may be shorted by only 1/2, as opposed to 1/9th of the baseline glowplug. Balanced against more difficult starting of the engine and the stress that places on the engine/starter/etc (which are more expensive and complicated repairs than replacing the glow plugs), the updated glow plug relay may make more economic sense in the end. IMHO

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Der Panzermann und Fraulein Fahrvergnuegen

1991 420SEL 201K "The Big Blue One"
1985 300DT 205K chassis/285K engine nee California emissions "Goldbug"
1983 300TDT 255K "The Womble"
1983 300 DT 214K "Sea Sprite"-Rear-ended a truck
1983 300SD 285K "The Donor" Gave his life so that others can live
1980 500SL Euro 105K "Der Panzer"

I agree, I would do it again even if it shortens the GP life by half. Glow plugs are cheap and very easy to replace (on a 616/617 anyway).

I don't want to make you fellows jealous, but, you haven't lived until you've seen a 617 start in 1.5 seconds at 12°F..........after a 15 second glow........and idle perfectly smooth..........like it was 75°F. ambient............who needs afterglow??............

Nice, but rebuilding the head is cheating.

I have one 617 that would be hard to start at 12°F after three cycles of the glow plugs.

But I have another 617 that could start at 12°F with 10 seconds of cranking and NO glow plugs. This one is impressive.

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

That is amazing. I have not attempted to start this one without glow plugs at those temps. I don't think it could do as well.

Mine gets finicky with one bad GP in cold weather, with two bad GPs it probably will not start below 10 or 15F. I have started it at -10F with a couple of glow cycles and a bunch of cranking, but everything has to be perfect.

When I lived in MN, I had a 300TD which (admittedly) had a rebuilt head about 10K earlier. I had trouble starting with a relatively new conventional battery. Switched to an Optima and never had problems again. Also used Extra anti-gel and would park in a garage. These things can be started at low temps, you just have to prepare for winter (which I did mid-October each year). Another one of my fav ideas was having two keys. you'd park at the grocery store and leave the car idling and locked.

__________________
Der Panzermann und Fraulein Fahrvergnuegen

1991 420SEL 201K "The Big Blue One"
1985 300DT 205K chassis/285K engine nee California emissions "Goldbug"
1983 300TDT 255K "The Womble"
1983 300 DT 214K "Sea Sprite"-Rear-ended a truck
1983 300SD 285K "The Donor" Gave his life so that others can live
1980 500SL Euro 105K "Der Panzer"