W202 C240 (1997) spark plug change

tjamesbo

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Just when my W124 is laid up with a seized key the wifes c240 has started missing and chugging a bit . I have it booked in for a Diagnostic with Howard Williams in Brum ( very good ) but would like to put a new set of Plugs in first anyone know is it easy on this engine???? I will use the technique of using a hose on the end of the plug to manually re-engage the thread before tightening with the wrench.

Also am I right in thinking that running with a misfire can damage the Cat ??
( ie if it is a cylinder not firing )

Thanks
 

turbopete

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from memory of the last petrol 202 i worked on, which was a 4 cylinder c180, the plugs should be fairly easy to get at. i usually thread the plugs in (re engage the threads) using the plug socket and the extension bar only and turning it by hand rather than with the ratchet! and yes you can damage/ruin your cat by running with a misfire!
 

jberks

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I did the 240 engine in an E. Some plugs were easy enough but others were at the back so quite hard to reach. I'd imagine the 202 would be more cramped than my 210 so it may be challenging.
Remove the engine cover (obvious but I didn't initially) and I believe removing the coil packs may help too.
I'd also change the leads at the same time as they tend to deteriorate and cause weak misfires that manifest themselves as an idle knock.

And yes, running with a misfire for any period can damage the cat.
 
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tjamesbo

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Anyone confirm what the Plug change interval on the 240 V6 is ??? I thought it was 60 k and I had bought the car at 67k with full MBSH so didnt think it would need doing until 120k ( and presumed it was done at 60k ) maybe a mistake its dangerous to assume anything
 

turbopete

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you could ask for a print out of what was done at the last service at MB. i believe this can be obtained at any MB dealer
 

jberks

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Hi,
I bet the spark plugs were missed, as it can be very expensive getting them done at MB, try this link below, its a "HOW TO" on changing the plugs on a V6 M112 engine, some very good pics, and descroption of the job.
http://cryptiksouls.co.uk/mercedes/plugs/index.html

I wish I'd had that when I did mine.
I managed it with the cover and coil packs in place, using an array of bars and a ratchet - suffice to say I don't recommend my technique!
 

LYNALL

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Much easier with the coils out of the way.

Did wifes c320 recently m112 engine back 2 awkward but not hard at all.

Dont forget there are 12 plugs.

Test each plug lead with an elec meter set to ohms the correct reading is on the side of the plug cap ie the metal bit.



Lynall
 
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tjamesbo

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Hi,
I bet the spark plugs were missed, as it can be very expensive getting them done at MB, try this link below, its a "HOW TO" on changing the plugs on a V6 M112 engine, some very good pics, and descroption of the job.
http://cryptiksouls.co.uk/mercedes/plugs/index.html

Great article I went to local dealer to get the spanner .... if £15 makes the job easy to do then I'm in ! Dealer said he couldn't sell to me as it was a "workshop tool " ( i didnt dare tell him I have a whole box full of spanners at home ! ) so i suppose its .....try my 17mm Spanners or buy a plug cap extractor tool and hope its still as easy. Obviously you can buy them from the dealer otherwise how did the guy who wrote the article know the price .

Do they not want £15 of my money or do they think I'm not going to do the job myself What a load of Jobsworth.
 

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Great article I went to local dealer to get the spanner .... if £15 makes the job easy to do then I'm in ! Dealer said he couldn't sell to me as it was a "workshop tool " ( i didnt dare tell him I have a whole box full of spanners at home ! ) so i suppose its .....try my 17mm Spanners or buy a plug cap extractor tool and hope its still as easy. Obviously you can buy them from the dealer otherwise how did the guy who wrote the article know the price .

Do they not want £15 of my money or do they think I'm not going to do the job myself What a load of Jobsworth.

Like dip sticks, I am sure that MB are breaking the law by refusing to sell these things, it comes under restrictive practices act
 

turbopete

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any decent supplier of tools to the motor trade should be able to supply you with the tools required!

also on the subject of restrictive practises act, ive heard a rumour that things like not remedying corrosion or other faults with guarantees outside the standard warranty solely due to not having a full manufacturer service record may also be banned soon! thatd be great for anyone with an early millennium merc thats used indies for servicing!
 

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any decent supplier of tools to the motor trade should be able to supply you with the tools required!

also on the subject of restrictive practises act, ive heard a rumour that things like not remedying corrosion or other faults with guarantees outside the standard warranty solely due to not having a full manufacturer service record may also be banned soon! thatd be great for anyone with an early millennium merc thats used indies for servicing!

Very true as we are free to have cars serviced at a place of our choice
 

vijilants

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You can use a normal 17mm spanner for the front ones but the rear ones can be real hasstle to remove.

Whatever you DON'T pull on the lead as the leads are expensive to replace.

An angled set of spark plug boot pullers help.

I did this job a few months ago .......it takes a lot of patience and it takes time :)....Unless you are Olly and Ive witnessed him do it in less than 30min !!!
 

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You can use a normal 17mm spanner for the front ones but the rear ones can be real hasstle to remove.

Whatever you DON'T pull on the lead as the leads are expensive to replace.

An angled set of spark plug boot pullers help.

I did this job a few months ago .......it takes a lot of patience and it takes time :)....Unless you are Olly and Ive witnessed him do it in less than 30min !!!

I saw him do that too :D:D:D
 

MB TECH WARRINGTON

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I have changed mine twice at 40-50 K intervels on my C320. 12 plugs.

What surprised me was, the gap was no difference between the old and the new, very little carbon build up and no difference in performance at all.

Next time, I will wire brush them and re-insert the same plugs rather than spend money on new one.

And then the end of the plug may drop off into your cylinder, seen it happen.
The intervals are there for a reason,
 

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And then the end of the plug may drop off into your cylinder, seen it happen.
The intervals are there for a reason,

So there is the danger of this happening if you go too far with them
 

turbopete

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wire brushes should never be used on plugs anyhow! there can be splinters of the bristles can stick to the plugs and make them short out etc! the correct official method for cleaning spark plugs is by an air fed 'sandblast' unit and a clean air jet to clear the threads etc!
 

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W202 C230K Auto 2000
W202 C230K (2000) spark plugs

Hi All

I have an interest in spark plugs at the present time and I purchased a set of 4 NGK triple electrode spark plugs this weekend. Halfords had Bosch plugs but I chose the NGKs instead. Today I purchased a 300mm, T-handled spark plug wrench in a sale, a real beauty, for under GBP7.00. This swivel-headed, magnetic 10mm tool is from the Draper Expert range. I couldn't believe my luck.

I have been reading this thread with interest which relates mainly to V engines. I assume that since I have an inline 4 engine a spark change will be simplicity itself. However, I'm not one to take things for granted and I was wondering if there are any hazards to look out for? It has been a while since I changed the plugs in any car and I've never worked on my Mercedes to any great extent. I've left the engine and ancillaries alone and I have had no trouble whatsoever. [all my fingers crossed]

I assume access to the spark plugs and their removal is simplicity itself with the correct tool(s). However, I have been wondering about the coil packs which I assume sit atop the spark plugs. Presumably they must be removed first to reveal the spark plug tubes? During refitting, are there any special torque tightening procedures required, i.e. plugs, coil packs, etc?

I assume the adoption of twin spark plugs per cylinder post dates my engine which I assume only has 4?

There is also mention of HT leads in this thread and the 'deterioration thereof'. I remember this poblem from years ago. I didn't think coil packs had HT leads associated with them, but maybe I'm wrong? I should think swapping a coil pack is no more difficult that replacing the ignition coil in a much older motor? [giving my age away]

The last spark plugs I replaced were torque tightened. I think it was either 18/24 Nm. Is this still true today because I have heard of spark plugs being hand tighten and then given a 1/2 to 3/4 extra turn? I have seen a stripped thread before and therefore I feel more comfortable using a small torque wrench.

I mentioned above buying a set of triple-electrode spark plugs. What is the standard fitment in Mercedes engines? I assume the preferred make is Bosch but what about the electrode configuration? Is a triple more reliable than a double or single? Does the electrode configuration place different demands on the ignition system?

I have also been thinking about spark plug sizes. I'm old enough to remember 18mm but with dual overhead camshaft engines the spark plug size has gradually reduced because of better design and materials. What is the most common spark plug size in Mercedes engines? Is 14mm still used? I have seen an 8mm [not in a Mercedes] but this must be a motorbike or outboard motor spark plug, surely?

Lots of questions but I look forward to your answers.

REGARDS

Phil
 

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