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Old 06-26-2015, 02:18 AM   #1
bikemaniac
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Smile Oil leaking from rear spark plug

Hi,

On my rear spark plug (the cylinder close to the fire wall) oil is seeping out on the head when driving at high speed. When idling and driving slowly no oil leaks out. The oil travels along the spark plug threads - even though the plug is tight.

When looking at the spark plug itself, the tip is grey, but the rim has a char buildup. All the other 3 plugs are bone dry with grey tips,

Is is most likely that the oil comes from

1. Piston rings
2. Valve seats

... or how can I test where the oil comes from?

Lucas
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Old 06-26-2015, 02:25 AM   #2
Mike V. Florida
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Default Re: Oil leaking from rear spark plug

A leak down test will tell you if you have a problem.

https://www.fordbarn.com/forum/showpo...36&postcount=7
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Old 06-26-2015, 04:13 AM   #3
colin1928
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Default Re: Oil leaking from rear spark plug

If your spark plug only oils up when at speed (low vacuum) then it is oil getting past the rings
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Old 06-26-2015, 09:19 AM   #4
rocket1
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Default Re: Oil leaking from rear spark plug

If you have a good spark plug gasket and the plug is nice and tight you should have no leak from the thread area.If it is a two piece plug could be leaking from the upper threads.
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Old 06-26-2015, 02:28 PM   #5
29spcoupe
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Default Re: Oil leaking from rear spark plug

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I had oil leaking from the rear spark plug until I fixed the drain tube on the rear main. Fixed the drain tube, leak stopped.
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