GEMcLean

My Feedback: (3)

I have been having a chronic problem with my muffler coming loose on my DLE 55RA. It started after about 200 flights on my Mustang.

So far I have tried:

• RTV on the bolt threads. (Lasted 2 Flights)
• Star washers and Red Loctite (Lasted 11 Flights)

Anyone have anything that is foolproof?

HELP!

Thanks,

Gordon

coralcape

My Feedback: (4)

Drill bolt heads and tie all together with stainless wire. Good luck, red

GEMcLean

My Feedback: (3)

Thanks, but bolts are inside the muffler.

a70eliminator

Tap threads in the muffler bolt hole recess area and tighten in a jamb screw, end of problem as bolt can't back out now.

acerc

Remove the gasket, apply a thin layer of Permatex Form-A Gasket #1, apply the Permatex to the bolt threads inside and out, put it back together. But be warned, it will not come back apart easily if needed.

Gizmo-RCU

My Feedback: (27)

Replace the bolts with new hi grade bolts then do as acer suggested. I had a similar problem at least partially due to the cheap low-grade bolts supplied with the engine a DLE 55. The new bolts fit much tighter right off.
Good luck!

Truckracer

My Feedback: (19)

+1 for not using the supplied gasket and using higher quality bolts. Along with that, in planes like a Mustang that have tight cowls, rear exhaust engines seem to be more prone to muffler problems than side mounted ones due to lack of cooling in the muffler area. That muffler is tucked in tight behind the cylinder. My bet is that your engine has less than ideal cooling and that muffler mounted on the back of the cylinder is also hotter than it should be. Improve the overall cooling of the engine and most if not all of your muffler problems will go away. In the long run, your engine will be happier also.

VincentJ

Gordon, have you tried using Nord-Lock washers? Here's a link if you've never heard of them http://www.nord-lock.com/

If you have a Fastenal store nearby you, they can be purchased through them. I have stoped using thread lockers such as the blue Permatex on all of my bolt threads ( as long as I can install a Nord-Lock ) with great success. Never had anything come loose! Good Luck...

SkidMan

My Feedback: (17)

Big thumbs up on the Nord Locks. Your bolts will not back out and they are reusable.

speedracerntrixie

My Feedback: (29)

Some how I feel somewhat validated here. I have been telling guys for years that 80% of the time a muffler working loose is because the engine is running too hot. Thanks Truckracer.

GEMcLean

My Feedback: (3)

Thanks, Everybody,

Today I have tried

• New Muffler
• New Bolts
• Stock Gasket
• Star Washers
• Permatex Exhaust Repair on threads and heads

If this works, I'll let you know.

In the meantime, I'm gonna try to find Nord Locks.

q-500

My Feedback: (1)

Check the motor mounts and balance the prop.

Truckracer

My Feedback: (19)

If you have a new muffler did you get the special bolts that mount it? Newer DLE mufflers now come with special tapered seat bolts. Standard bolts will no longer work properly with the new mufflers. Also not mentioned in this thread, be sure the exhaust flange on the engine and the muffler are flat. I usually surface these with a sanding block. Some use sandpaper on a glass or other flat plate. If perfectly flat, you really don't need any sort of gasket and a sealer such as Permatex Ultra Copper or something similar can be used very sparingly just to seal any remaining imperfections. Note that in the automotive world, most exhaust manifolds are bolted directly to the cylinder heads with no gasket of any kind.

I'm skeptical of using star washers on a muffler bolt. I would think that over time, with the heat and vibration present on our mufflers, the star washers would dig into the aluminum muffler allowing the bolts to loosen. Split washers (or Nord Locks) are more common as they provide the greatest flat surface contact between the bolt head and the muffler.

WI53072

+1 on the Nords. My DLE 35 came with them. They work well.

propicts

Because of the amount of heat generated by the engine, blue thread lock will not work. I have the same engine and other DLE's, I always use high temp thread lock ( white ) on the
muffler and mounting bolts, with no problems !

GEMcLean

My Feedback: (3)

To VincentJ:

Thanks for the tip on the Nord-Lock Washers! I an using them now. So far 25 flights and no sign of loosening.

I'll keep you up to date as more flights get done.

Gordon

Truckracer

My Feedback: (19)

While Nord Locks can work in many cases, they will not work with the new DLE tapered seat bolts. Nord Locks require flat surfaces which the tapered seat bolts and mating surfaces inside the muffler can't provide.

I still maintain, keep the muffler and engine cool and 90+ % of the loose muffler problems will go away!

SIX GUNS

GEMcLean , I had some thing similar with my RCGF 45 engine and 1 thing I did is to put a strap from the muffler to the engine that cured
the problem for my engine. I think that the aluminum muffler that is expanding and contracting so much, that mite be a contributing factor
along with the vibration from the engine . Have you thought of using a different muffler ??


Jim

Lifer

My Feedback: (1)

On my DLE 20RA I used bolts long enough that the head extended slightly past the outside of the muffler. I found a fender washer of the correct size to cover the entire bolt opening. Omit the gasket, used copper gasket paste, and high-temp red loctite. This method was used on a cowled engine approximately 2 years ago with no further problems.

Best regards.

preed5270

You only think the DLE 55ra has special exhaust bolts. The inside of the muffler is flat not cone shaped or concave as the bolts supplies would have you believe. Standard 5mm socket head will work.
Peter Reed

Truckracer

My Feedback: (19)

Maybe the muffler you looked at didn't have a tapered bolt seat in the muffler but the DLE 55 and 35 mufflers I just looked at were indeed tapered .... as were the ones I looked at in the past.

SIX GUNS

ForcesR

I have two 55RA's and I have never had the muffler/muffler bolts loosen up since being installed three years ago. The bolts and washers are all stock items that were supplied with the DLE engine. The method I use is install the muffler before the engine is installed in the aircraft. I tighten the bolts as tight as I can with 1/4 inch drive ratchet and socket. Then I take my heat gun and set it to maximum heat and heat the muffler flange and engine muffler attachment flange where it bolts onto the engine. I direct the heat to the top of both flanges and then to the bottom of both, alternating from top to bottom every minute. I do this for a minimum of ten minutes and then retighten the bolts. The bolts will tighten another 1/8 turn or more from where they were first installed cold.

Roger