Spark Plugs

[markjay]

On my Toyota and Renault, the spark plugs needs to be chaged by mileage only, not time - 36k in the case of the Renault, and 63k (probably translated from 100k KM) on the Toyota which has the Iridium plugs. In fact tha Toyota is now 12 years old and due to low mileage (40k) is still on the original plugs and with FSH.

However MB say that spark plugs need to be chaged every 56K miles (probably 90k KM originally) or 4 years... surely they use the same plugs as everyone else - e.g. Bosch, NGK, etc - why do the plugs need replacing every 5 yaers on my C180K?

 

[moonloops]

On my Toyota and Renault, the spark plugs needs to be chaged by mileage only, not time - 36k in the case of the Renault, and 63k (probably translated from 100k KM) on the Toyota which has the Iridium plugs. In fact tha Toyota is now 12 years old and due to low mileage (40k) is still on the original plugs and with FSH.

However MB say that spark plugs need to be chaged every 56K miles (probably 90k KM originally) or 4 years... surely they use the same plugs as everyone else - e.g. Bosch, NGK, etc - why do the plugs need replacing every 5 yaers on my C180K?

One of two reasons:

#1 for the money
#2 as the plus I have seen changed after x years are knackered (massive plug gaps) and seize into the cylinder head

 

[jefrs]

On the MB
a) there's a dozen of them.
b) they are totally inaccessible.

use a little anti-seize grease to stop plugs welding themselves in.

 

[jefrs]

BTW they are supposed to be inserted into a cleaned hole by hand (the knurled bit is for the fingers to grip), and then nipped up with the torque wrench. Not thrown in with an air-tool.

 

[lil.smartie]

Worst plugs we've seen came out of a 2 yr old Smart with 2000 miles on, lots of short journeys kills them!

Kate

 

[Will]

I have to say, wouldn't fancy trying to take out spark plugs that have been in for 12 years. Might be fine, might be siezed in - after all that time can't the expense be justified?

Surely mileage, although useful as a guide, doesn't accurately account for the possbile wear/damage to the plugs. Say if that 40,000 miles was mainly all around town (quite possible over 12 years!) the plugs could be in a very poor state as Kate mentions above.

 

[vijilants]

The multi-prong plugs generally last far longer due to the fact that the spark only jumps from the central elecrode to one of the prongs, the closest prong. As that one wears down, it then starts using the next prong, and so on.

However I don't think that it is the greates of ideas to keep a set of plugs in a car for 4 - 5 years due to the fact that you could land up with issues getting them out if they have been in there for soo long.

 

[jefrs]

I had problem with a spark plug ejected by a TR7, it was a bit high compression, a special aluminium head "helicoil" kit fixed it without removal of the head. I've never had a problem with seized parts on Volvo 245, in fact I've never even heard of any screws seizing on them. I ran the Volvo with the triple electrode plugs, one set lasts many years and the do improve mid-range performance: they never, ever seized. The hole must be cleaned before insertion otherwise grit and gunge is forced down the orifice.

Spark plugs are supposed to be put in at low torque, there is a compression washer that does the tension job and it must not be crushed flat. The correct spanner will remove them. A long arm on the spanner, such as the torque wrench helps, but do not hit them, that can damage the threads in the head. Aluminium head is soft, steel spark plugs are hard.