rcfan450

I have a 4 yr old Saito 82. I bought it new, broke it in nice and easy. It has been the sweetest, smoothest, lowest idling engine I've owned. Until recently....

About 3 flights ago it started cutting out (not dieing) and popping. About 2 flights ago it did it really bad and actually sounded like rods were hitting the piston (it did die this time) but they didn't cause I tore the motor apart and checked. Everything looked great. Then on it's last flight it died while in a hover, about 20' up. Ya, that didn't end well.

So that brings me to the question - do glow plugs wear out?

That's about the only thing I can think of that was the issue with the motor starting to act wierd. I will put a new plug in it soon to see if it runs any differently but thought I'd throw the question out there and see what I got.

If there are any other good threads already written on this subject, please direct me that way.
Thanks!

Mr Cox

Glow plugs do "wear out" (especially during the running in of a new engine or storing for a long time) and the catalytic reaction is not what it should be. One indication is that the engine runs better with the glow driver on compared to when it is removed. Just swap it for a new glow plug and see if that helps.

rcfan450

Makes me think I should replace all my glow plugs. I have some pretty old engines with the original plugs in them. They seem to run fine for now but I don't want anymore issues like I mentioned above obviously.

So next question then: Do you replace your glow plugs on a regular basis?

Sport_Pilot

They get colder as the element gets thinner.  Also corrosion of the element makes them colder.  Sometimes cleaning them helps.  But eventually they wear out.

MJD

My Feedback: (1)

Yes, they wear out. Pretty much repeating what others said, as they age they may glow brightly and the engine will start an run fine with power applied to the plug, but the surface of the glow element over time becomes "poisoned" with various deposits, reducing the catalytic action. Listen for the rpm drop when you pull power at idle, that is one strong clue.

I replace my plugs whenever the behavior changes as power is removed. Or whenever the engine generally acts up for no other reason. I would say that "many" times in the field over the last few years, I have fixed a balky engine by swapping plugs. The best example of this is with my one-and-only four stroke - a Saito .72. I see a very significant change in its behavior with a deteriorated plug, especially idle reliability and transition, and have swapped plugs on it 3-4 times in the field and made it run sweetly again.

I always tell people, when in doubt try a new plug. Some people stubbornly leave old plugs in on the premise that if it starts with the driver on, the plug is good. Not true whatsoever. Sometimes it feels painful to toss a $5-$10 plug, but it's better than re-kitting an airplane, and a smooth running engine makes for more enjoyment and less stress - ain't that what it's all about?

rcfan450

Copy that MJD and others. I'm gonna be making a shopping list of glow plugs tonight as I go through the fleet to see what I have. It needs done.

Bob Yeager

My Feedback: (5)

+1

C185Pilot

My Feedback: (25)

How fresh is your fuel? Any fuel opened more than a month is not fresh. Methanol is hygroscopic (it absorbs moisture). Fuel is made with anhydrous methanol and if it has absorbed moisture it will not catalyse properly and thus the poor idle and unreliable running even with a new plug.

Mike

rcfan450

This is a good point, it was old - but that was the last of that gallon so now I'm on to a new gallon.

MajorTomski

I believe the .82 is a four stroke? When was the last time you adjusted your valves?

rcfan450

Quite frequently actually, I check those on all my 4-strokers at least twice a year. The last time for this motor though was after every flight it started acting wierd, that was the first thing I checked. It was the same each time - perfect.

MajorTomski

I have also had "new" botlles of fuel be bad too. Gives the same result.

Have you changed props? Have you verified the prop nut is tourqued tight enough?

rcfan450

I have wondered about getting bad "new" bottles from the shop before. I try to find the cleanest looking bottle, meaning it was put on the shelf most recently.

The prop nut was tight, but I can see your point there. If there is any slippage that would create issues big time.

ArcticCatRider

My Feedback: (6)

I know some guys who change the plugs on their more expensive models every X number of flights. Like others have said, glowplugs are high up on the troubleshooting checklist when things aren't going to plan.

I wouldn't just change them frivolously though, unless you're really worried. I think glow plugs have come a long way, as have their reliability. I have some plugs that have literally several gallons of fuel through them. Some are a couple of seasons old. BUT..it's all about peace of mind. I change out my nylon wing bolts once every year or two..people think I'm crazy, I just think one less thing to worry about.

airraptor

My Feedback: (66)

there are sopme ways to clean the deposit's of the wire. On any new engine i always use a old glow plug to break it in even if i have to leave the glow heat on for it. why mess up a brand new plug if the engine comes with it.

also if you start to blow plugs and nothing else is change i would look at your rear bearing as it may be on the way out...

huck1199

Are the elements in plugs plated or is the platinum alloyed in the wire material?

fourstar40

My Feedback: (27)

I have a greatplanes Cub 40 that has OS 52 surpass engine on it. I have had the cub and engine around 8 years and still has the original glow plug in it. So sometimes it takes along time till they were out.

MJD

My Feedback: (1)

AFAIK they are usually platinum-iridium alloy.

do335a

There is not one thing in our universe that does not ultimately wear out. That includes glow plugs, engines, model engine fuel which goes bad too and all osrts of other things too, including us.

huck1199

Thanks MJD, someone said they clean them; how is this done?

MJD

My Feedback: (1)

I'd like to know too - I've never done it myself. I wonder what eats plug deposits but leaves the alloy alone?

jeffie8696

Plugs will get contaminated from metal shavings during the breakin or a bearing failure so its a good idea to check the bearings if you are having plug trouble.
Plated elements were tried and failed.
You can get a new jug of bad fuel, it has happened to me from a brand name manufacturer and he explained to me that if the filling dept is stopped for some reason the anti foam agent can seperate and go to the top, then the last bottle filled get a huge slug of it which causes the idle to be "problematic". Thats why I am in the habit of shaking my bottles before each refueling.

JPMacG

My Feedback: (2)

I can tell you my experience - not that yours will necessarily be the same. I fly a Saito 72 and a Saito 100. Between the two I probably have used 20 gallons of fuel.

I've had to replace the carburetor-to-head gaskets twice on the 72 because it developed air leaks and the engine would not idle or tune properly. I had one gallon of fuel go bad, and that was when the jug was nearly empty. I've tried replacing glow plugs several times when I was trying to diagnose a problem but each time the new plug was no better than the old, so I went back to the old.

Your problem may differ, but based on my experience I'd say get a new gasket kit from Horizon (only a few bucks) and replace the gaskets. Go ahead and try a new glow plug and new fuel first - that's easy.

By the way, I use OS F plugs and 10% nitro. Higher nitro might cause plugs to go bad more often.

JPMacG

My Feedback: (2)

I would also say that replacing glow plugs on a schedule - like every year or every 5 gallons of fuel - is costly and probably not necessary. Just keep a couple new glow plugs in your field box and try one when you think something is wrong. Then, if it doesn't help put the new one back in your field box. I keep a new OS-F for my Saitos and a new Enya #3 for my 2-strokes in my field box.

jeffie8696

Ihave had the orings go bad on my Saitos before too, easy fix.