Cleaning spark plugs

They're not that expensive £14 for my car and for the Punto at least only need changing every 24k miles. I happy just to pay £14 every couple of years and give them an inspection, check the gap and light clean every other 12k. In all honesty they still look fine after 24k and the car has the same performance and mpg.

A friend brought round a tool for cleaning them. You put it in what looked like a large pencil sharpener and it sprayed the plug with a grit of forms. It came out looking the same but was now coating in grit :D

Regards,

Tim

Matt used his keyboard to write :

It leaves traces of abraded metal from the brush on the ceramic nose of the plug which then has a tendency to short it out and cause a misfire.

In the days when plugs did need regular cleaning, they used grit and compressed air in a machine made specially for the job. I seem to remember some also included a plug tester, which put the plug under high pressure as if in the cylinder and checked it for break down under high voltage.

In those days I used to always drive with one set in the engine and a second set clean and ready to be installed in the boot.

With modern lean burn engines there should be no need to clean the ceramic nose - all they need is the colour checking and the gap. Colour simply to check the state of combustion in the cylinder.

do NOT wire brush, ever. it wrecks the plug.

Cleans them.

No. Only if the electrodes are severley worn or the insulation cracked. Usually they just need regapping.

Ahh. I normally have them changed at the 10k service interval, just as good measure really. I was curious about regapping, say you take your plug out and the bit at the end has come out a bit what does you use to push it down and re gap it.

if the plug has been used long enough to alter the gap (it is the spark jumping which principally tears tiny bits off one electrode), then the set of plugs should be replaced. the days of plug maintenance are long gone. the gap used to be adjusted by bending the side electrode. Plug efficiency drops after about 3000 miles (with old type standard plugs) new plugs have far better lives, but still need regular replacement, one of my cars specifies plug replacement every 63,000 miles ! some are even higher, most are 10 - 30,000 intervals.

Mrcheerful

Afternoon Mrcheerful,

I see. I think I'll just stick with changing them on full services. Interesting stuff, I always see a neighbour a few doors down brushing his spark plugs with a little brush what uinitially got me curious. I guess at the cost of them now its simpler just to replace them and have the peace of mind there done.

There is little point changing them before the recommended intervals.

The constant plug cleaning is one of those self rolling balls, you wire brush the plug, after a few miles the tiny amounts of metal that you have rubbed into the insulator start to track the spark and you get a misfire, so you wire brush the plugs, etc. etc.

In the good old days, spark plugs could be dismantled, cleaned and rebuilt.

Mrcheerful

I'm actually old enough to have done that!

The old days were not necessarily good IMHO. I much prefer just putting a new set of plugs in my Focus every 40k.

Chris

I just tap mine on the rocker cover and check with feeler gauges.

You can buy a proper tool but IMO, they're not that necessary.

Utter bollocks. So because the plug gaps on my wifes Mondeo needed redoing after 10,000 miles, I should bin the plugs even though their service life is three times that?

why did they need re-doing? was it running badly? or were you just playing?

even over their service life by quite a bit plug gaps scarcely change. people fiddling with them does more harm than good.

I was doing the 10,000 service on the wifes car. I always pull the plugs to check how its running and check the gaps.

On 2007-06-06, Matt wrote: [...]

It's not even the cost. On newer cars you take them out after 30k miles and they look practically like new, you can still see the little "v-grooves" on the electrodes. Amazing.

They used to get covered with crap in only 6k miles or less, and you'd compare the exact shade of crap carefully against the only page of the Haynes manual which is printed in colour for precisely that purpose. Maybe your neighbour has an old MG or something.

These days you should change the plugs when the electrodes have rounded off their sharp corners and the gap has widened a little which is probably at the same mileage as when the manufacturer says. Re-gapping won't fix the rounded electrodes and rounded electrodes need a much higher voltage to generate a spark which puts more stress on the HT leads and coils, making them more likely to fail.

Conor wrote in news:MPG.20d0e1743a2a6ddd98aa49 @news.karoo.co.uk:

Plugs on my "test to destruction" Volvo were in for over 200,000 miles, still worked perfectly.

That's impressive.

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "MrCheerful" saying something like:

Back in the 50s or earlier. I recall coming across some of those ones in the 70s, but they were really old stock.

used to use a little bit of kit called a sandblaster...