Glow Plug Insert Leaking

Iceberg Sat Jun 20, 2020 12:24 pm

I recently purchased some glow plug inserts. After noticing one was a bit low on compression tried some soapy water around it and noticed that the center pin was slightly leaking. Has anyone ever experienced this before? I haven't run the plug yet but will it seal up after getting hot and a run or two? Just never saw this before.

Thanks
Iceberg

Ken Cook Sat Jun 20, 2020 12:39 pm

Fireball plugs are notorious for having the insulation blow out. Just like Fox plugs. However, the Fireball shorts seem to do better in terms of longevity and the insulation staying intact. I gave up on them. Years back, they were mediocre and did what they were supposed to do. I used them in older baffle period engines that aren't generally finnicky. I would use these engines once or twice a year therefore it wasn't as important to me to throw in a better plug. The problem I see is your location in terms of purchasing a plug or plugs that'll serve you better. One thing I would recommend is if you have some JB Weld, you could place it around the post and hit it with a heat gun. This may offer a leaky plug new life. Even epoxy isn't going to hurt to try.

aspeed Sat Jun 20, 2020 4:12 pm

I epoxied my Fireball shorts before using them, and they still blew the seals. Maybe motors with lower compression would last a bit longer.

balogh Sun Jun 21, 2020 1:47 am

If you stop the leak the pressure under the JV weld or epoxy will be about the same as in the cylinder because there is no flow and friction loss towards the seal. But this pressure (I assume the peak can be 15...20 bar or 200..300 psi when the engine runs) will throw the weld and epoxy off and the leak will start again..

I would buy new plugs knowing also, however, that COX engines will lose power with normal plugs and only turbo plugs with their tapered sealing tip can retain or even increase compression ratio.

Darren I am not sure about hobby supplies in Thailand and understand you need to cook with what you have there. But maybe ebay, or Bernie and Matt can still ship to you?

Iceberg Sun Jun 21, 2020 2:36 am

Thanks Andras
Will find out.

Talk soon
Darren

davidll1984 Sun Jun 21, 2020 4:40 am

som glow plug leak not the coper seal on tread center pin loose leak is imposible to fix u can try to pres tight back with right tool dont no if is posible never try my self found 1 after hard crash engine start run bad wit closer look plug works ok just leak buble on very top on center pin seal it was .074 cox part not os

aspeed Sun Jun 21, 2020 11:11 am

Got to watch out for those crashes. I was wondering if crimping the housing would work too. I have a couple cards of Fireball plugs. The old Goodyears ran well with the Cool plugs on high nitro.

Iceberg Sun Jun 21, 2020 12:40 pm

I tried a fix on the plugs I have right now as want to get them... off the ground up in the sky!

I first pass put super glue into the seal around the leaking pin. Then put vacuum on the inside of the plug while the super glue was still liquid. This drew up a little bit of the super glue into the red insulation that was there. The leak stopped 100% I can assure you. Then after 8 hours I added a little epoxy all around the stud as suggested by some of you. Letting that cure as properly takes 24 hours. I will try them and hope the little sweethearts hold tight. In the battery clamp they still glow bright and orange so no residual super glue has leaked onto the filament. Hopefully this might do the trick.

When I looked up super glue has a useable temperature range to just over 300 degrees Fahrenheit. Epoxy is higher maybe closer to 400 degrees. Am I correct that the cylinders while running in an airplane with airflow over them will run in the mid 200 degrees? As far as I can tell maybe close to that. Well the burn marks on my fingers say hotter but... Laughing

I'll update after some flight time.
Ice

aspeed Sun Jun 21, 2020 1:39 pm

The dune buggy guys always are checking the head temps, and around 180 to 230 is normal. Maybe the plug would be a bit higher. I would assume that is in F degrees as they also test with a drop of water. I will be waiting for the results. Hope I didn't throw away my old leaky plugs. Probably did.

happydad Mon Jun 22, 2020 12:22 am

aspeed wrote:The dune buggy guys always are checking the head temps, and around 180 to 230 is normal. Maybe the plug would be a bit higher. I would assume that is in F degrees as they also test with a drop of water. I will be waiting for the results. Hope I didn't throw away my old leaky plugs. Probably did.

Is anyone aware of any cox .010 glow heads leaking? That would help explain the lack of compression.

Happydad RC Plane

Iceberg Mon Jun 22, 2020 12:58 am

Hi HappyDad
The heads I have for my .010 have never had leakage issues? One seized on pretty bad but not leaking.

Ice

happydad Mon Jun 22, 2020 1:25 am

Iceberg wrote:Hi HappyDad
The heads I have for my .010 have never had leakage issues? One seized on pretty bad but not leaking.

Ice

FYI I was in Central Thailand in 1969-1970 with USAF. Worked with Opals and black Sapphires in the base gemshop to keep out of the heat.

Happydad RC Plane

aspeed Mon Jun 22, 2020 10:11 am

To see where the leaks are, you can squirt water or fuel over the head and turn the motor over with the prop to look for bubbles. Often the head gasket/shim has a piece of sand or dirt and it will leak from there, or there is a dent in the head or cylinder where it seals. A wet and dry test for the piston/cyl. is just add a drop or two of oil to the piston and see if it bubbles there. Pretty basic stuff that will tell a lot.

Iceberg Mon Jun 22, 2020 1:28 pm

HappyDad
I hear you about the heat. I'm in Bangkok as hot as it gets. AC gem shop would be awesome escape.

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