Black Oil Goop Explosion

[Pilot Ben 28]

 

 

 

Whilst flying my normally 100% fuss free wot trainer the engine cut, no biggie. On landing the engine was covered in black oil/gunk coming from the exhaust and cylinder head itself, and it won't re start. I'm bringing it up on Sunday, but any ideas until then?

 

 

 

B

 

 

[Trevor 25]

Might have been running too lean and overheated. We can have a look on Sunday

[Pilot Ben 28]

 

 

 

Thanks Trev and a happy new year. I'm a bit embarrassed to admit that I had just tuned it myself

 

 

 

Anyway, see you then

 

 

[Pilot Ben 28]

Last week the carb stuck, the week before it chucked the prop off and smashed the spinner, and this week it produced gloop. It used to be a ultra reliable engine....

[Martin 0]

 

 

black oil/gunk coming from the exhaust and cylinder head itself

 

 

 

Oily residue from the exhaust is normal, though obviously more than usual may indicate something wrong. If there is genuinely residue coming out somewhere other than the exhaust or a tiny amount from the front bearing, this is definitely a problem! Have a look to see exactly where it seems to be coming from, and also check that everything that should be tight is. Is the plug still tight? Is the silencer still tight? Is the cylinder head still tight? Don't force anything tighter than it should be, but do check to see if things are loose. Heavy bits attached by a couple of screws (such as silencers, rear needle assemblies, etc) have a tendency to vibrate screws loose. I once lost one of the screws that held the backplate onto an OS 46 LA because they also held the rear needle assembly - when I noticed the problem one of the screws was gone and the other one holding the needle assembly was loose by several threads. (The engine still ran fine in that case though - I just noticed the needle valve rattling when I was refueling for another flight...)

 

 

 

Of course, if there is a lot of oily residue coming from the silencer it may have just covered everything else and there may not be a specific leak. I would also check the plug - if you ran the engine very rich it would produce a lot of residue and may have gummed up the plug. Everything covered in "black oil goop" sounds like very rich running to me.

 

 

 

Is there anything else unusual about the engine? Is there any discolouration to the engine after you've cleaned the oil off? Does it feel different when you turn it over slowly? Did you notice anything unusual before the engine cut (e.g. a loss of power)? What were you doing at the time (e.g. mid-throttle circuit flying, or part way through an aerobatic manouevre)?

 

 

[Pilot Ben 28]

 

 

 

I was in a full power climb out. It just died "normally", no noise or unusual occurrence, just the regular cough cough stop. The engine appears fine, turns over nicely. I'm wondering if its something deeper wrong as in the past month its been a very sad engine, and before that it was perfect.

 

 

 

Anyway I'll run it on Sunday and see what happens. Considering the plane cost me £45, I'm fine with taking it up with a dodgy engine

 

 

[Peter Royall 47]

 

 

 

sounds like cylinder bore/piston damage to me. Hope its not for your sake.

 

Oily

 

 

[Pilot Ben 28]

 

 

 

I'll strip it down today to see whats what.

 

 

 

TBH I'm not really fussed that much. The engine cost me about £10 if that, so I figure flying it for the whole of summer and most of winter is a fair trade. If its all gone to pot I know where I can get a very cheap new 46

 

 

 

I cant imagine anything seriously wrong as it still turns over perfectly, and if there was cylinder or bore damage after a few turns something would have got stuck, broken or jammed?

 

 

 

See you tomorrow,

 

 

 

B

 

 

[Martin 0]

 

 

 

Well, when you say "turns over perfectly", does that include still having the same feel to the compression as it did before? Merely spinning round freely with little or no compression is a very bad sign!

 

 

 

But as you say, we can have a look at it tomorrow.

 

 

[Pilot Ben 28]

 

 

 

Well it runs, but is spluttering and is producing a lot of exhaust fumes that are what I would call a bit black

 

 

 

I have tried to tune it, but it keeps cutting when I even touch the needle.

 

 

 

B

 

 

[Pilot Ben 28]

Just thought if say it's now back to its reliable good old self!!!!

[Martin 0]

What was the problem?

[Pilot Ben 28]

 

 

 

It's honestly a mystery Martin!!! I really have no clue what caused it All that matters is that it's fine now!

 

 

 

 

 

B