ok, ive never replaced my glowplugs myself before, but ive decided to do it this time after having trouble starting in the cold, figured it would be pretty easy, right?

i pop the hood open today to take a look at it and it took me almost an hour to even find all of the glow plugs. each of the 5 is in a completely different position relative to its cylinder, not like the little picture in the service manual where theyre all lined up nicely(diagram of a different model).

i still want to do it myself though, i think.

i could use some answers to some questions, i know alot of you out there change your own plugs alot. if youve done this on a 2.5t before, i could REALLY use some advice.

first, what tools should i have?

should i replace them all, or just the bad ones?

and how do i find out which are the bad ones?

what parts do i have to remove to access all of the plugs and is it very difficult to replace them?

whats a good price on bosch plugs?

and lastly, is it just me, or do 2 of the plugs look bigger than the rest, at least from the outside? are these things ive spotted even the glowplugs?? i found them by followin the wires coming out of the GP control box on the driver's side of the engine compartment.

please help me out with all the advice you can spare, and thanks alot.

__________________
1991 300 D 2.5 Turbo, 220k
also in the family:
1981 240 D 185k
1991 350 SD 185k
2006 S 500
2005 SLK 350

The glowplugs are all the same (unless someone else replaced just some of them!), and are all in the same relative position on each cylinder, directly below the injectors.

You can remove them from the 602 with a deepwell socket, a swivel, and a long exentsion, but many owners prefer to remove the intake manifold for access.

I've not changed glowplugs on this motor, so can only provide guidance on testing and so fourth.

Good plugs have a resistance of about 0.8 ohm. You can check this by unplugging the connector at the relay and use an ohmeter between each of the five wires and ground. A bad plug will have higher, lower, or infinite resistance.

I'd replace all of them, if some are bad, likely the others aren't too far behind.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Definitely replace all of your glow plugs. In winter weather, it pays off bigtime.

__________________
Regards,
Aaron

thanks, i took a closer, better informed look at it and i found the other 2 glow plugs, they ARE all lined up and the same size.

BUT it looks like without removing the intake manifold i could only replace one.

do i have to remove the intake manifold? this looks like a pretty big job as all of the fuel lines are tied down to it. am i missing something? shouldnt this be easier to do?

thanks

__________________
1991 300 D 2.5 Turbo, 220k
also in the family:
1981 240 D 185k
1991 350 SD 185k
2006 S 500
2005 SLK 350

Unscrew the bolts on the crossover pipe from the turbo (get new gaskets) and undo the clamp bolt, then remove the nuts holding the intake on and pull it off.

You will want to clean out the crossover pipe and manifold, the collect coked oil and soot from the EGR (synthetic oil will reduce this considerably).

It is possible to remove the glowplugs with the intake in position, but it is a pain. You will need a 1/4" drive ratchet and some extensions, and a swivel. Ditto for the wires.

Make sure you don't twist the wires when you install them, they can break.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

It is possible to do it without removing the manifold. Get those tools you need as Peter mentioned. On this model you'll need to remove the Cruise Control unit from the manifold to gain some room.

__________________
BJ

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I've done this job both ways (manifold removed vs no manifold removal) I prefer to remove the manifold - it gives you a chance to lube the throttle linkage to the injection pump and inspect some of the harder to access coolant hoses. The manifold is not that hard to remove.

One piece of advice I can give you is if you remove the manifold use some duct tape to cover the intake ports- its easy to drop a nut down the intake port and then you are screwed.

Don't ask me how I know.....

Tim

It just takes some clever manuevering and lots of patience.

thanks for all the good advice. ill probably do it this weekend. is it necessary to replace the gasket between the intake manifold and the connecting air pipe? or can i put that off. does anyone know the part number for it?

thanks

__________________
1991 300 D 2.5 Turbo, 220k
also in the family:
1981 240 D 185k
1991 350 SD 185k
2006 S 500
2005 SLK 350

Grdenko,
You do not have to replace the gasket if it is still in good shape. I just changed all 5 glow plugs today. I removed the intake manifold to make it easier and replaced the intake to head gasket. I also replaced my themostat today, but I'm having a problem getting the air out of the cooling system. Any one have ideas? The thermostat is from Autozone.

Jim

Jim:

You will have to "burp" the system -- squeeze the hose to the coolant tank, install the cap with the hose sqeezed, then let go. This expands the air bubbles some. It also helps to have the car parked on a good slope nose up.
You will probably have to add coolant for a while until all the air works out.

The heater core also holds air badly, and will gurgle for a while after you get the coolant filled.

Did the Autozone thermostat have a bleed valve in it, and did you put it in with the bleed valve at the top? No to either question means get the t-stat in correctly (won't self bleed if you don't) or get a proper thermostat.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

psfred, thanks for you response, I have all working well now, I found out I had the thermostat in backwards(what a bonehead). The Autozone thermostat did not have a air bleed hole in it so I went with the MB OEM one from the dealer. I wanted to go with a more for sure bet. After cheking the old stat over it was not closing all the way. Heats well now, runs about at 85 deg. C

Jim

thanks for all the responses

i tried replacing the plugs myself but gave up after no being able to get the crossover pipe off. i was able to get it off of the manifold side but not the turbo side. i took the screws out but the crossover pipe, or the 'charge air pipe' as its called in the service manual wouldnt come off. i could move it around but couldnt get it off, it felt like it was being held on with rubber or something.

is the charge air pipe held on at the turbo side with anything other than the 2 screws and the the angled bracket they go through?

after i gave up i took it over to the shop and had them do it, so its all good, but maybe next time

__________________
1991 300 D 2.5 Turbo, 220k
also in the family:
1981 240 D 185k
1991 350 SD 185k
2006 S 500
2005 SLK 350

I believe the charge air pipe connection to the turbo has an "O" ring around it and you need to twist and pull to get it off. Maybe you could do the job if there is a next time.

JT