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1976 280SL, 1979 450SL
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Discussion Starter #1
So I've owned my 1979 450SL for a few months now, and I've put around 2k miles on it or so, and it still drives, and strong too (never driven or been inside another one to know if it's supposed to drive better), but I have a few "problems" that need diagnosing. My car accelerates and breaks great once it's warmed up, but upon a reputable Mercedes mechanic hearing my car run, he told me that it's definitely not running smoothly. I don't have money for him to take a more detailed look at it and fix it himself (I work on my own cars and am really handy), but I want to make the car run nice and smooth before putting it up on the market.

First off: the old spark splug wires were completely Mickey Mouse and worn out and even cracked in a few spots where they go onto the spark plugs, and sparks were visible at a few of the places where the spark plug wires attach to the spark plugs when the car was on (at night obviously since during the day it's far too bright for sparks to be visible). I bought new NGK spark plug wires and changed them out myself and thought that my problem would be fixed. Well, the car does run a bit smoother now (juts a tad bit; maybe it's in my head), but the other night I noticed that there are still tiny sparks around some of the spark plugs, right around where the spark plug wires go onto the spark plug (it seems the sparks are between the spark plugs/spark plug wires and the actual engine). What could be the cause of this problem?

Another annoying problem is this really rough grinding noise that I hear sometimes while I'm driving. The noise usually occurs in the lower gears (haven't ever noticed it in the last gear), and is always gone after I switch to a higher gear by accelerating and then letting go of the gas pedal to allow the transmission to switch gears (my car's an automatic). If I don't switch to the next gear, the noise will go on slowly while my car is coasting, and speed up when I press on the gas pedal, and it won't stop until I switch gears. It sounds like a rusty fan with thick metal blades rotating and grinding and hitting something every time it's rotating. Has anybody else ever encountered anything like this? What could that be?

If everybody is as stumped as I am with these two things, then I could try and record the noise with my phone, but I don't know if the noise will be heard too well due to the lack of quality, and the video will have the same problem. I stay in Berkeley, CA and would love to have somebody swing by if they have any free time or I can drive out to within an hour's radius.

Thanks a bunch for all of the help beforehand, and I wish you all the best of luck with your own cars. Again, if anybody would like to help me out in person, I can drive out within an hour's radius or so of Berkeley, CA (I would drive further, but I don't want to risk the mechanicals failing on me in the middle of nowhere).

Erik
 

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500SLC #2624. Black on Black.
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5,120 Posts
Firstly, only use OE spec ignition leads on these cars, you cannot use generic leads and have it run properly. They need to be copper core and the have the correct resitance. Get some Bosch leads, will not set you back much (about $70 or $80), just make sure that they are made specifically for your car.
 

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2005 SLK350, 91 300SL with Pano Top, 04 S500, 2015 Tesla Model S
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2,085 Posts
You really should also replace the spark plugs or at least clean them and gap them to the proper spec. Also check the distributor and rotor for carbon traces.
Now that grinding noise is disconcerting. If you don't know when the last time the transmission oil and filter were changed, do that immediately first.
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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29,512 Posts
If you don't know when the last time the transmission oil and filter were changed, do that immediately first.
Ha!

Spoken by a man with experience.
 

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1976 280SL, 1979 450SL
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26 Posts
Discussion Starter #5
Fotografa: NGK is not some generic manufacturer. They specialize in spark plugs and spark plug wires, and they're made specifically for each and every model of any car. From the specs of the wires and pricing and just plain physically looking at the wires, the NGK wires are better than the Bosch ones (in this case; other cases may vary).

mrelbe and nobby: I will change all of the oils and filters of the car soon, but I always get Mobil 1 synthetic oils, and I'm not wanting to buy those oils for no reason if they are going to be drained a short while later and gone to waste. If I had money to throw away, I would, but I'm just a college student that loves working on cars and having them run smooth and efficient.

Thanks for the input so far guys!

Nobody has ever encountered such noises or sparks in the places I mentioned?
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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32,363 Posts
I am sure Foto will appreciate the information but missed the point on the leads. What are the specs?
As for the spark. Cracked porcelain. Plug boots not properly seated.
Did you change th plugs too? What plugs are you running.

Take a moment and fill in your profile with car and location.
 

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500SLC #2624. Black on Black.
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5,120 Posts
I've shopped around a lot for plug leads for these cars, but have never come across a set made by NGK to MB OE specs, with copper core and the correct resistance and exact correct connectors/suppressors at each end.
That does not mean they don't exist, just that I haven't seen them. Genuine MB (Beru), are best, followed by Bremi, Karlyn and Bosch.
Where did you buy the NGK's?
I was not suggesting that NGK are some generic brand, but I do know for a fact that NGK make a range of generic leads that you can buy from your local auto parts store. You do not want to be using those.
 

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W221 & Audio Moderator
2013 S550
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10,980 Posts
Fotografa: I will change all of the oils and filters of the car soon, but I always get Mobil 1 synthetic oils, and I'm not wanting to buy those oils for no reason if they are going to be drained a short while later and gone to waste. If I had money to throw away, I would, but I'm just a college student that loves working on cars and having them run smooth and efficient.
You might want to reconsider using any synthetic oil in your car, unless you are certain that is what has been run in it from the beginning. There are many ---- OIL THREADS!!! (OK, guys, relax) ---- but take a look at http://www.benzworld.org/forums/r-c107-sl-slc-class/1554372-zowee-hundred-dollar-oil-change-two.html for some recent discussion.
 

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1976 280SL, 1979 450SL
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26 Posts
Discussion Starter #9
The "model name" for the NGK spark plug wires I got is EUC050; they're made specifically for our cars (and a few other V8 Mercedes). The sparks are not coming from not having a good fit on the spark plugs since I put them on myself and made 2340982398% sure they were on nice and tight and fit. One concern of mine: when I was trying to put on the spark plug wires, I had to unscrew the terminal nuts on the spark plugs because the spark plug wires' female connections to the spark plugs were too small to fit with the spark plug wires on the spark plugs. I read online that some applications are just like that, but maybe I was supposed to push hard enough for the NGK spark plug wires to "stretch" to the spark plug terminal nuts? Anybody else have experience with this?

I haven't changed the actual spark plugs themselves, but the spark seems to be between the spark plug and wire combo and the actual engine. Would a faulty/cracked spark plug make tiny sparks be visible between the spark plug and the engine? Does anybody else have any other ideas to what might be causing the tiny sparks?

Also, any feedback on the noise that I'm hearing? I don't want to change the oils to find out that I wasted money for no reason (money is pretty scarce right now, even for an oil change).

Thanks for the valuable responses so far guys...:)
 

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One of the BW Old Guard/R129, W204 Moderator
1997 SL500- 40th Anniversary
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7,166 Posts
One concern of mine: when I was trying to put on the spark plug wires, I had to unscrew the terminal nuts on the spark plugs because the spark plug wires' female connections to the spark plugs were too small to fit with the spark plug wires on the spark plugs...
Which I interpret as not the correct wires, or not the correct plugs...
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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32,363 Posts
You did the right thing by removing the tip of the plug. You should hear or feel a click when the boot is properly seated on the plug.
 

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1978 280slc
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3,203 Posts
I'm across the bay in Belmont near san mateo. I'm no expert but if you need some help I don't mind. It sounds like either the plug ends or wires aren't compatible and the instead of proper ignition you are grounding out.

I'll send a PM, but I'm no expert. I can give you a good once over though. I make it over to Berk periodically and if I'm in town I might be able to swing by. I might even end up that way this weekend depending on if my car plays nice.
 

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It Is What It Is, Dude
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22,841 Posts
.


First off: the old spark splug wires were completely Mickey Mouse and worn out and even cracked in a few spots where they go onto the spark plugs, and sparks were visible at a few of the places where the spark plug wires attach to the spark plugs when the car was on (at night obviously since during the day it's far too bright for sparks to be visible). I bought new NGK spark plug wires and changed them out myself and thought that my problem would be fixed. Well, the car does run a bit smoother now (juts a tad bit; maybe it's in my head), but the other night I noticed that there are still tiny sparks around some of the spark plugs, right around where the spark plug wires go onto the spark plug (it seems the sparks are between the spark plugs/spark plug wires and the actual engine). What could be the cause of this problem?


If both wire sets exhibit the same problem, and the only other component in the area of the discharge still hasn't been changed...
 

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1976 280SL, 1979 450SL
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26 Posts
Discussion Starter #14 (Edited)
rowdie: thanks for the confirmation. i made sure to hear/feel them all sit firmly into place, so i know that the installation isn't the problem.

isthisdave: yeah, you're right, my plugs are probably the problem, but i just didn't think that fouling spark plugs could exhibit such behavior, but hey, i'm not a spark plug expert of any sort.

daryn: that'd be great to meet up and see what you think of my car and its problems. i don't know when i'll have time to drive to where you are since a lot is going on with me right now, but whenever you have time, just give me a ring or a text on my cell phone and we could meet up. if i see that i could make it to belmont, then i'll let you know...818-468-7682

to all: i'm looking at getting the accel 8181 spark plugs (8 pack for unbelievably cheap price of $17 from kragen; usually they're $3.50 each at the cheapest place)...does anybody have a better option that's around the price range of $1.50-$3 a spark plug (or maybe a horror story from using accel spark plugs)?
 

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1976 280SL, 1979 450SL
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26 Posts
Discussion Starter #16
so i changed the spark plugs, but i'm still running quiet rough. i'm going to change the motor and transmission oil and filters within the next few days and see if that fixes much (i hope at least the grinding noise goes away)....:/

does anybody know a place or somebody that could tune my mercedes really good for a reasonable price here in the bay area? i definitely need to get it tuned, and i think that would solve all the problems, but i'm no mechanic to say 100% if that's the case. i'll say this much: gas could be smelled like crazy when my car is on, and that's an indication that it's running crazy rich. it's either too much fuel or not enough air, but i don't think the air is the problem. eitherwho, if someone could recommend a place i could go to get my mercedes tuned perfectly for a few twenties, that'd be greatly appreciated...:)

erik (818) 468-7682
 

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1978 450SL (RIP); 2007 Impala 9C3 (Police); 2010 Ford Edge
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212 Posts
Another annoying problem is this really rough grinding noise that I hear sometimes while I'm driving.
Erik
long shot - I had a car with a dented ring gear cover which interfered with the ring gear only at certain speeds and sounded really bad. I pounded out the dent and the grinding noise went away. Of course, state of the fluid and its level should be the first check. That's my $0.02.
 

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1976 280SL, 1979 450SL
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26 Posts
Discussion Starter #18
long shot - I had a car with a dented ring gear cover which interfered with the ring gear only at certain speeds and sounded really bad. I pounded out the dent and the grinding noise went away. Of course, state of the fluid and its level should be the first check. That's my $0.02.
where is this "ring gear cover" that you mention? i'm new to the mercedes world, and i don't know the location and names of the parts (although i'm really good with my hands; i used to fix rx-7s and rebuild rotary engines).

also, regarding the noise, it doesn't seem to be only at certain speeds, and it's moreso in certain gears only (usually in second and third, but now it seems it's throughout any gear at "lower" speeds). it used to happen rarely a few months back, but as time went on, the frequency increased, where as now it's happening every single time i'm driving around town at low speeds in every gear. the noise speeds up or slows down depending on the rpm.

again, if anybody knows a trustworthy mechanic in the bay area (berkeley, oakland, san francisco, etc) that can tune older mercedes for a reasonable price, please let me know. i need the air/fuel ratio fixed because my car is running super duper rich, which is making me go to the gas station and become poor
 

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1978 450SL (RIP); 2007 Impala 9C3 (Police); 2010 Ford Edge
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212 Posts
Now, I'm a newbie too, so these cars may not even have a cover like that.....I thought if I threw that out, it might prompt someone with more background or maybe connect a dot for you.....
 

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Always Remembered RIP
1979 280sl 4 sp w/ac 1957 MGA 1998 volvo xc/70 2004 F150
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6,050 Posts
By ring gear I assume you mean flywheel and the noise possibly being it hitting the cover
 
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