Cleaning glowplugs

[John Carrodus]

I've been unable to fly for the last 7-8 months. Some of my models that were running fine a year or so ago have now got plug issues. My clubmates tell me the plugs deteriorate when they have been used and left sitting around in the model.

   Q- can this be prevented -  and can it be corrected? ( sonic cleaning??)

This is rather irritating as plugs at up to $25NZ is more than what some of my engines are worth and an expensive PIA!!

[Brett Buck]

I've been unable to fly for the last 7-8 months. Some of my models that were running fine a year or so ago have now got plug issues. My clubmates tell me the plugs deteriorate when they have been used and left sitting around in the model.

   Q- can this be prevented -  and can it be corrected? ( sonic cleaning??)

This is rather irritating as plugs at up to $25NZ is more than what some of my engines are worth and an expensive PIA!!

     I have never heard of or experienced that.  I have used engines that haven't run for many years, and in some cases with no after-run, put them in an airplane, fired them up and flown official flights with them with no practice. They ran exactly the same as when I took them out of the airplane years ago.

      I would rather suspect that you have a bunch of gummed-up oil making the engine run change, particularly if you use a lot of castor oil. The solution is to either run it a lot, or disassemble and crock pot it if it is bad enough.

   Changing the glow plug might change the way it runs, a new one sometimes runs different from an old one. but that is almost certainly not the issue here. Even then, with proper fuel and proper settings, glow plug also last at least many hundreds of flights and I can't recall any recent examples where it ran significantly different if I changed it.

      Brett

[Dan McEntee]

I've been unable to fly for the last 7-8 months. Some of my models that were running fine a year or so ago have now got plug issues. My clubmates tell me the plugs deteriorate when they have been used and left sitting around in the model.

   Q- can this be prevented -  and can it be corrected? ( sonic cleaning??)

This is rather irritating as plugs at up to $25NZ is more than what some of my engines are worth and an expensive PIA!!

   I can't remember where I read this, some one on this list or on FB, but they were taking the cast off plugs from his R/C buddies, soaking them in acetone or some other solvent, gently blowing them dry and they using them with no problems. I'll agree with Brett in that they just may be full of oil and some other tiny debris. You could try a short burst in an ultrasonic cleaner to loosen stuff up. Just use a strong detergent/cleaner/degreaser and then flush with fuel carefully. Attach a battery and see what it looks like, then test run.
  Type at you later,
   Dan McEntee

[Lauri Malila]

When a plug starts going bad, the first thing you notice is a carbon- or whatever buildup in the colder part of coil near the spot welding in the bottom of plug body. It’s easily visible and can be scraped away with a sharp scalpel, using a magnifying glass or under microscope. That will give some more lifetime to the plug.
For anything deeper inside the plug, I wouldn’t bother. Just change the plug, it’s a cheap insurance.
I rarely have much difference in run with a new plug, usually it’s just better as the gradual worsening has been unnoticed. I also center the coil in every new plug and push/pull it to the correct distance from the mouth of bore, I guess that makes them all quite similar.
That being said, I didn’t change the plug last year, and it still looks like new. But I use no castor oil. L

[Motorman]

If they're caked with dry oil that's pretty bad. You could soak them in a strong alkaline cleaner if it won't burn off with the battery. Need more info.

[944_Jim]

I'm a cheap SOB...what's cheaper, the plug or the plane? For Roundie-Roundie over concrete, who cares? Try all you want. For Roundie-Roundie-Upside-Downie? New plug...or new plane. Your choice...but I'll say I lament the day I trashed a 1960 Scientific profile P-40. It looked great doing only wing-overs. Not so great the day it flamed out upside down.

PS I can do inverted, inside loops and outside loops only...so I'm no expert.by any stretch.

[Larry Renger]

The acid used for cleaning swimming pools (muriatic acid) will freshen up glowplugs. Don’t use on aluminum glowheads, it eats the aluminum.

🤠

[EricV]

Other than tater build up from certain fuels*** or blown or distorted coils from cheap plugs or over compressed pre-detonating engines, glow plugs should last a good long time. Storage isn't really a factor unless the chamber was filled with old castor oil/fuel and allowed to sit several seasons. I can't imagine why you would be experiencing this issue.

If you really think something is going on, perhaps save up some old plugs this season, clip the tips off or paint them red or something so you can differentiate them, and set them aside as "storage plugs" and put them in your engines over the off-season until you are ready to go fly and put your working plugs back in.

As Brett and others have stated, "something else" more likely is going on, like varnished up sleeves, water intrusion in your fuel, solidified castor in your fuel lines/filter/engine, etc. Plain bearing engines like Fox35 get the crank gummed up pretty bad if stored with castor residue... but it's pretty obvious what is going on there when you go try to start it, heh. Just pay attention to what is going on, start eliminating factors, and see what stands out that is left.

Hope that helps,
EricV

***All that said... when a certain type of fuel (of which I had bought several cases) turned out to be a major "tater producer" I went through an expensive period of changing plugs pretty regularly. It wasn't fun. It usually showed in a ratty run that would clear up inverted (gravity helped clear the plug a little, who knew?) so I learned to recognize when I started getting a ratty upright run with a leaner inverted flight, I had a tater formed. I'd pull the plug and look, yup, a big old blob on the bottom coil. Change the plug, smooth as silk again. That was not a fun period. I went to PowerMaster Air after that, that problem (and others) went away.

[John Carrodus]

Many thanks guys. I have plenty to review and work on there now. A bit of a head scratcher, and something that needs to be fixed. I suspect too much caster oil, might be a good place to start.
Cheers
 From Down Under where Kiwis fly upside down in NZ