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Current 1992 - 500SEL, W124 - 1989 230E (sold)
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Discussion Starter #1
Guys do you know which of these plugs are better for my 500SEL
i would assume they are pretty much same just some temperature difference depending on your climate...
My car has a sticker with F8DC0 under the hood but most of the online shops recomment F8DC4

Anybody knows whats better?
 

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2014 CLS63S SB
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1,159 Posts
Don't know anything about those numbers but I have the Champion EONs in my 500. Haven't had them in long enough to comment. One thing I do know though is that Benz lumps seem to run really hot. It's the only brand of car I have had that builds up so much heat under the bonnet that when you open the door to get out it's almost like you get engulfed in a big invisible cloud of hot air. Now although the block should run at a set temp, I'd say bear that in mind.
 

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Current 1992 - 500SEL, W124 - 1989 230E (sold)
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Discussion Starter #3
I did bit of research online, and F8DC4 is apparently better and can replace F8DC0 ...so i will stick with F8DC4 plugs.
 

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Buncha W124's
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Resurrecting an ancient thread... F8DC4 is the standard plug with 2.6mm center electrode, these are commonly available from the dealer or from some aftermarket vendors.

Bosch F8DCO plugs have a larger 2.9mm diameter center electrode. I believe these plugs are NLA and have been out of production for quite a while. MB superceded them to F8DC4. I think the F8DCO were MB # A0031593003.

Remember to ONLY use non-resistor plugs, especially for 80's/90's engines with EZL ignitions & distributors. F8DC4 are correct, FR8DC/FR8DC+ are wrong, no matter what the cross-reference or catalog says. If your mechanic insists that resistor plugs are fine, get a new mechanic. And never, ever use fancy-electrode plugs (platinum, iridium, yttrium, etc)... the older MB engines really dislike those.

While we're on the subject, open up the gap from the factory spec of 0.8mm to 1.0mm on the F8DC4 plugs. This can help eliminate the intermittent hot idle hiccup.

Misc spark plug photos are at this link.

:sawzall:
 

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'99 S420 119K
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1,452 Posts
Great Advice About Plugs!

Resurrecting an ancient thread... F8DC4 is the standard plug with 2.6mm center electrode, these are commonly available from the dealer or from some aftermarket vendors.

Bosch F8DCO plugs have a larger 2.9mm diameter center electrode. I believe these plugs are NLA and have been out of production for quite a while. MB superceded them to F8DC4. I think the F8DCO were MB # A0031593003.

Remember to ONLY use non-resistor plugs, especially for 80's/90's engines with EZL ignitions & distributors. F8DC4 are correct, FR8DC/FR8DC+ are wrong, no matter what the cross-reference or catalog says. If your mechanic insists that resistor plugs are fine, get a new mechanic. And never, ever use fancy-electrode plugs (platinum, iridium, yttrium, etc)... the older MB engines really dislike those.

While we're on the subject, open up the gap from the factory spec of 0.8mm to 1.0mm on the F8DC4 plugs. This can help eliminate the intermittent hot idle hiccup.

Misc spark plug photos are at this link.

:sawzall:
Dave, thanks for posting this info. Pics are wonderful.

So many folks just don't "get it" when it comes to plugs. I'm having a discussion over in W124 about this, too. Champions in a Benz? Seriously? Who does that? A 60 cent plug in a $50-100K vehicle? :confused:
 

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97 SL500, 98 E320 Wagon - former W108/W111/W112/W114/W123/W124/W126/W140/W220
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Dave, thanks for posting this info. Pics are wonderful.

So many folks just don't "get it" when it comes to plugs. I'm having a discussion over in W124 about this, too. Champions in a Benz? Seriously? Who does that? A 60 cent plug in a $50-100K vehicle? :confused:
I have never understood the reasoning behind trying to second guess the people who originally designed the car, not to mention the economics. When I can use what the OEM recommends as replacements and they're less than aftermarket parts, why would I do otherwise?

:confused:

Dan
 

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1999 S500; W140.051
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775 Posts
FWIW, I have used iridium plugs in a number of old MB motors M114; M115 & several M119's as well as Volvo 6-cyl alum block B6304's without any problems at all.

Indeed, M119 motor went to iridium plug in'98.

Everyone is entitled to opinions, but sharing about basis of opinion is more important than the opinion.

Iridium is a very unusual element that extremely resistant to ablation by the electrical arcing while still being a pretty fair electrical conductor with resitivity about 3X of copper & 2X of aluminum. What iridium brings to the party is the ability to make very tiny exposed electrode which also has extremely long service life.

Anyone who has experimented with high voltage 10-50 kV knows that making the point of the electrode smaller makes it easier to get an ionizing plasma going at lower voltage.

The iridium allows a much smaller electrode, arcs at a lower potential. The tiny exposed electrode stays cleaner, has better duration of arc and lasts longer.

I've been using the NGK iridiums for years. The plugs can easily last 50-70 kmiles; look good and have the gap measure 1.2-1.3X the initial setting.

The only downside to iridium for this application is that it is extremely brittle matl. One has to be very careful to not break the electrode in gapping.
 

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93 190E 2.3, 94 E320 (sold), 01 E320, 99 S320, 18 Durango
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Dave, thanks for posting this info. Pics are wonderful.

So many folks just don't "get it" when it comes to plugs. I'm having a discussion over in W124 about this, too. Champions in a Benz? Seriously? Who does that? A 60 cent plug in a $50-100K vehicle? :confused:
I ordered plugs from MB union Nj for my w201 few years ago and when I went to pick up the plugs it was champion plugs as mentioned in the owners manual.
 

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'99 S420 119K
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1,452 Posts
Iridium

daidnik,

Thanks for the information. you make some excellent points. I can see an application for iridium, I just don't know if gasoline and oil engines are suited to small electrodes and long service life. Natural gas fired emergency generators would be one application, however.

My limited experience proved to be a disaster, fouled those Bosch iridium plugs in under 100 miles. I honestly forget what vehicle I put 'em in, maybe an older Benz. It may have been bad valve guides/seals, who knows? :crybaby2:

Anyway, I pull plugs every 15-25K to see how the firing chambers are functioning. I want to see wear, i want to see color, oil, fuel, whatever on the plugs. To be safe, I use what the dealer suggests, and if the owners manual suggests more than one option, I go with the Bosch. I never had an issue with Bosch copper plugs, call me an old fashioned, last century dinosaur.

I haven't touched my new to me '99 S420's engine yet, and you mention the iridium plugs are spec'd for the M119 engines '98 models. This should be an interesting experience for this old dog**shakes head**.

Hamada,

The dealer offered you Champions? I'm eating my hat as we speak! Ha, ha, ha. :wave:
 

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'99 S420 119K
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1,452 Posts
Could It Be

I ordered plugs from MB dealer for my W210 and they were Champion plugs
Something about NJ? Ha, ha, ha...just kidding.
W210 and W201? <<scratching head>>

Decades ago(admittedly) I saw several instances where Champions, A/C Delco, and Autolite suffered from broken insulation. Apparently installers were cracking the insulation and as it got hot it broke? :nerd

Also, Bosch offered the removable copper/aluminum tops exposing the threads on the top of the plug which was the industry standard for the German wire/plug configuration.
 

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'99 S420 119K
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1,452 Posts
Yttrium

Ok, you fellas got me looking up this spark plug stuff.

Bosch F9DOC is the plug recommended for my 99 S420, M119.

It's a Yttrium plug.
There are Beru and Champions listed also. I'd didn't look them up for the Yttrium application.

https://en.wikipedia.org/wiki/Yttrium
 

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1999 S500; W140.051
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775 Posts
I was wrong about the plug change in '98 for M119. Change was to laser welded platinum electrode. Design principle was same as with iridium ... reduce electrode area for arc ignition while retaining longevity. It doesn't seem like Bosch grabbed on to iridium for consumer vehicle application, but they have a line of industrial engine plugs using iridium on both electrode & ground.

Interestingly enough iridium has melting point 1200 deg F higher than platinum. NGK was issued a patent for the basic idea of the iridium tipped electrode and/or ground electrode in 1988. I think the really dark art to the use of this matl is in the method of joining metals with widely differing melting temps.
 

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93 190E 2.3, 94 E320 (sold), 01 E320, 99 S320, 18 Durango
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@LogicalPosition, The dealer didn't give me options to choose from. I told them i want to order plugs for my W201 and they gave me the plugs inside Mercedes logo box which had Champion plugs in it.
For my W140 S320 I ordered some plugs from Clark and it was Bosch plugs inside the MB packaging.
 

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W140 1994 S500 USDM base model, before facelift
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618 Posts
As long as all ignition specialists are already on this topic... :)
I'd like to pick you brain a little:
I just replaced rorors and distributor caps and all spark plugs. Specified bosch plugs no resistors, as recommended. old plugs were ok, but a bit darker then they should be, looks like they were changed once over 60k. 2 plugs were not tight for some reason. I had slight hesitation on idle before and i still have it now :(

So, any ideas what may cause it? Engine is running fine on any rpm but idle, if ac is on hestitation is not there. It is very minor, you can hear slight miss every 30-40 sec.

Bosch spark plug wires are purchased and going in next... But still is it going to fix it? And if not what a hell is it? Engine sounds perfect pulls hard, no any other issues.

I did not check the gaps on spark plugs, but they come preset usually. At the time i did not know about increasing a gap to 1.0, is it worth trying?

Ah also, i drive and then stop, hesitation will not be there, as well as if i race the engine it will give me couple minutes of clean idle. If it sits ide for some time, then i can feell it, again very slight.
 

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Ok, you fellas got me looking up this spark plug stuff. Bosch F9DOC is the plug recommended for my 99 S420, M119. It's a Yttrium plug. There are Beru and Champions listed also. I'd didn't look them up for the Yttrium application.
Where are you looking this up? In the Mercedes/dealer EPC, or in Bosch catalog?



@LogicalPosition, The dealer didn't give me options to choose from. I told them i want to order plugs for my W201 and they gave me the plugs inside Mercedes logo box which had Champion plugs in it.
For my W140 S320 I ordered some plugs from Clark and it was Bosch plugs inside the MB packaging.
Mercedes offers factory plugs from several different manufacturers, typically Bosch, Champion, and Beru. There are different part numbers for each but are all interchangeable. Depending on price and availability, you may receive any of the 3, unless you ask for a specific brand / part number.



I had slight hesitation on idle before and i still have it now :(

I did not check the gaps on spark plugs, but they come preset usually. At the time i did not know about increasing a gap to 1.0, is it worth trying?
Yes. This is easy and free. See if there is any improvement with the gap at 1.0-1.1 mm.



Bosch spark plug wires are purchased and going in next... But still is it going to fix it? And if not what a hell is it? Engine sounds perfect pulls hard, no any other issues.
It is very unlikely that new wires will fix it. However, you can measure the resistance of your old plug wire ends/boots. Spec is ~2000 ohms and if they are within about 20% of spec they are ok. If you find any that are very high (say, 5k-10k ohms, or higer) that could be part of your problem. Assuming your new M119 wire set is the type with orange plastic plug boots and light gray wire, be VERY careful laying the wires into the plastic X-tray. The gray insulation is fragile and tears easily. This won't affect performance if it tears, but you'll feel better if you don't damage them in the first place. The X-tray has numbers on the bottom which tell you how to route the wires, they should all fit neatly in place. But the aftermarket wire lengths probably won't match OE, so you'll need to get creative to make everything fit nicely...





 

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W140 1994 S500 USDM base model, before facelift
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Thank you for the suggestion and pictures!
Is there anything else which can cause the hesitation?
 

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Thank you for the suggestion and pictures!
Is there anything else which can cause the hesitation?
Do you have a hesitation under load, while accelerating? Or just the intermittent idle hiccup when warm, every 30 seconds or so? One other thing is the engine mounts... if they are not recent, they are probably toast.
 
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