LEO .46 Kinda like Model Engine Company of America (MECA)
KB-1L glowplug. Dunno who makes it.
Twice in a row this has happened to me, so I suspect it's not the glow plug:
I install a new glow plug. The engine will run fine for a couple of days, then I will start to see bubbles coming out of the middle of it right where that metal something-or-other sticks up. That metal thing is 1 contact and the case is the other.
I then start to have engine problems. I find myself richening the fuel mixture to get it to run, but only roughly. I replace to glow plug and everything goes back to normal.
< 10 flights with this engine and I've change the glowplug twice. Got another engine exactly like it with ~ 20 flights and the same plug.
Any ideas what can be causing this? Anyone see anything like this before?

That is a K&B plug. The "thingy" is the center electrode. Go ahead and use an OS8 plug instead or maybe an A3.

http://www.neweramodels.com/cgi-bin/...ky&part_id=981

I think bad insulators -- which is to say, bad plugs.

I don't think I've heard of anything an engine will do that consistently breaks the pressure seal between the insulator and the electrodes. Running hot/lean would probably kill your engine before it killed a glow plug in that particular way.

Have you tried different brands of plug yet?

sounds like a naff plug to me... maybe your running too lean? ive read on the Model technics website about the two different metals in the plug seperating if the engine is running too hot, maybe try running it with a richer mixture or try a different brand of plug (Novarossi are one of the best )

No idea what a LEO .46 is, buy you're not running a long plug in an engine that needs a short one by any chance? Especially a plug with an idle bar. If the piston is tapping it you'd have more problems than bubbles, I would imagine., but if it's only hitting it at full throttle it may be more "sneaky".

http://www.osengines.com/accys/glowplugs.html
OS plugs.

http://www.mecoa.com/acc/glowplug/glowplug.htm
K&B Plugs The 1L is NOT an idle bar plug.

Leo .46
http://www.justengines.unseen.org/Leo46.htm

No, but I assume the "1L" indicates it is long. Try a K&B-1S or a Fox #8 Short. Some engines have high compression and low headroom.

The plugs are blowing the insulating seal which is fairly rare nowadays but still not unknown. Once the seal goes the engine loses compression which can make them hard to start and then they run poorly as well. It's not a fault of the engine. Lean running will usually just blow the coil.

I plugged mine into the "starter" jack on the power panel once. that killed it pretty quick!

Thanks for the replies guys. I haven't tried different plugs. The only hobby shop within 100 miles carries only 1 brand of plugs.
I'm definitely not running the engine lean. If anything, I run my engines too rich. I don't think that could cause this problem...
I'll throw a third plug in the engine and post on here if it dies within 5 flights or not.
It's on my trainer, which doesn't get as much action as some of my other ones: only when my wife wants to learn some more about flying. Could long periods of inattention cause this?
Cheers!
G

It shouldn't.

Hi!
Try this! Hold the airplane straight up! It should be able to run slighly rich in this position.
The glow plug of choice is an OS 8 or Enya 3 and fuel containing 5-15% nitro

Hi ger88005
I have had the same experience that downunder mentioned. Running too lean damaged the plug and it started to leak from the top. It happend 2-3 times before I figured it out. It only took a few flights for the plug to be damaged. In at least one instance the center contact could be moved. I don't recall the make of the plugs, but I have used Fox and OS 3 or 8 plugs. Once I corrected the lean condition the plugs last a long time. I try to always tune the engine for maximum reliability in the air, which means slightly rich. I NEVER tune for maximum RPM.

The way I tune my engine: lean it out till it reaches max rpm and then richen it about 3 or 4 clicks.
I'll make sure it runs rich before she flies again by holding the plane nose up.
I'll post if I find anything out of the ordinary.

Being an English product order, your Leo may be designed for low or no Nitro methane. In other words very high compression like FAI Pylon Racers and CL speed. Nitro is almost non-available in Europe, or at least very expensive. FAI competition requires 80% methanol and 20% oil. NO nitro.

The early ASP engines (O.S. Clones) were like that. More than 5% nitro and they may not run at all, especially the larger ones.

Grab a soft-drink can and cut yourself several head-gaskets. Add 1, then maybe 2. See what happens. My Asp .75 and .90 had to have them to run on even 10% fuel until they had several hours flying time.

In addition the K&B plugs are rather old technology for high performance engines. Try the McCoy 59 or OS/Enya # 3 or 8.

Back in the '50s most glow fliers used the CHAMPIONS. Yep those were cute little buggers. Then the first imported OS High Compression engines arrived on scene and "Whamo" those white elements simply aimed for the eyeballs. Change happened.

Running lean and trash or metal particles passing through the engine is the cause of almost all glow plug burnouts. I have not replaced a plug for any other reason in over ten years.

Bill

I apologize for not stating this to begin with, but I'm running 5% nitro on the engine that's giving me problems and broke in the engine that's not giving me problems with 5% and now run it with 15% nitro.
Until the engine runs reliably, I keep it on 5%.
This engine will stay on 5% until I get this issues resolved.
G

If plug number 3 does the same, I'd suspect a bad batch made it out of the factory. You may have to bite the bullet and mail order some different plugs. It's just painful to pay shipping on a small order.

funny enough, i just had a plug do the same thing to me last weekend. the pin was all loose and wobbley. granted i have been having a devil of a time keeping this engine running anyway, but i think all the abuse trying to start it might have overheated the plug and cooked it. worked out the issues with the engine and put a new plug in and it all seems to be ok now.