Spark Plug

[Dazz]

Hey

One of my spark plugs appears to be overheating and causing a heavy build up on the bottom. I have replaced the spark plug and also the HT leads. However every week or two i have to take it out and clean it up again, ive got the gap set to the correct distance and the dizzy cap is new and ive also rubbed down the rotor arm.

Haynes reckons it could be a worn valve guide? Is this likely to be the reason?

Thanks

 

[BRUN]

is it just the 1 plug then ?

 

[Dazz]

yeah the other three are fine, look exactly how they should. its just plug number 3 keeps developing a build up, firstly i replaced it for a new one, and now i just clean it with a wire brush every now and again.

Thanks

 

[BenR]

if its got buildup of carbon and depostis on it, its not burning hot enough......

 

[Chris_H]

what sort of buildup is it?

Carbon, oil, orange juice?

Hard, soft, slimy?

 

[Dazz]

its a hard white carbon build up. Takes a little scrubbing but it cleans up ok each time.

Any ideas?

 

[BenR]

get a pic...........you cant read a plug via words and descriptions of substances that you dont know the name of..........

you can tell alot about how an engine runs at any particular rpm, but if you let it idle, that plug now has no relevance to what your engine did at higher rpms..........possibly ceramic boiling evidence, but i doubt your plugs are really running that hot, unless its the wrong plug.

 

[Chris_H]

so its running lean then?

Air leak, burnt valve blah blah blah.

get a compression test done on it.

 

[BenR]

worn valve guide.......wouldnt be white........think oil.

 

[Dazz]

http://www.centuryperformance.com/images/tech/Plgashd1.jpghttp://www.centuryperformance.com/images/tech/Plgashd1.jpg

Theres a link to a pic of what the plug looks like, its pretty similat to that.

Hope this makes it clearer

 

[BenR]

jesus!

if it looks like that its ash........from poor burning of crud like oil........so either rings/valve stem seals or guides.

Is it on one side of the plug only or the whole thing coated in crud?

Do a compression test.

 

[Dazz]

I take it i just pop down the local garage for a compression test?

Yeah that pic isnt an exact copy, just very similar, its normally white rather than brown ash. I think last time i pulled it out it was only on one side of the plug.

Will using a hotter plug temporarily solve the prob or should i get it looked at asap?

Thanks

 

[BenR]

it wont solve a leak........sounds like you got oil comming in from one of (probably inlet) the valves.........

 

[Dazz]

ok, take it this is a job for renault then

any ideas on £

 

[BenR]

not just for ren, any competant mechanic can do it.....parts are only about 30-40 quid.

 

[Dazz]

So i guess im looking about £100 (two hours labour etc). So the best idea is take it down the garage and get a compression test done, then try to find out if it is the problem. What sort of results should i be looking for from the test?

 

[BenR]

comparisons between cylinders, leak down test, ring test.........they will or should know what to do.

2hrs labour........possibly, if they work fast. its a head off, press out, press in, lap back in job.

 

[Dazz]

Btw, would this be classed as a failure or general ware and tear, just wondering if id be able to get it done under warranty

 

[BenR]

ware and tear.

 

[BenR]

BTW, how extended is your warrenty then!!!!!!!! lol

 

[Dazz]

yeah hehe

nah i bought it from a garage a month or two back and it come with a 3 month mechanical breakdown warranty.

ah well, guess il have to get saving there goes the new brakes!

 

[Dazz]

Ben just one more question, if the prob is a small oil leak which it appears to be, will any additives have any effect, i know u can get stuff like radweld for radiator leaks, was wondering if any similar would work for the fuel system?

Prolly a crazy idea but worth asking

Thanks

 

[BenR]

nope............

get it to teh garage and tell them its a mechanical failure......just haggle with them. go on..........you might as well have a shot