Exhaust tubes out of muffler

Yesterday I had the cowl off of my RV-12 to install new exhaust pipes as per Service Bulletin 00005. I found both exhaust pipes on the left side had worked their way out and were sitting up on the muffler socket. I have attached a picture.

This RV-12 is new to me. I had some work done on it before I picked it up including new stainless steel exhaust springs installed when replacing a broken exhaust spring. That was only about 5 hours ago. Now one of the new springs has also broken and both tubes are out.

So what gives? I am wondering if this means I have excessive vibration or some other problem. Vibration doesn't seem excessive but like I said, this -12 is new to me so I don't have a lot of experience to judge by.

Vibration would certainly be a factor. If it hasn’t been done, a dynamic balance seems in order. And not factors in your specific issue, but it doesn’t appear there is anti-seize lubricant applied to the exhaust joints or that there is safety wire through the springs to retain them should they break.

Since the RV-12 is new to you.. register for a Van's Aircraft "Store" account and register your serial number. That will get you access to ALL the kit-build plans, not just the ones which have been updated over the years. You will want Section 48. This details the procedure on how to connect the muffler to the exhaust tubes. I suspect your problem is vibration + the muffler not being seated in the "least stress" position.

Essentially, the directions will have you loosen up all the nuts on the tubes so that they rotate freely at the engine-side of them. Hook up the muffler with all 8 springs. Move it around side to side.. Find where it wants to sit naturally.. then tighten up the bolts. (thats 4 pages condensed into 2 sentences). Don't forget to put silver anti-seize compound on the ends of those tubes!

I have a DynaVibe that I can send out to other RV-12 builders are nominal cost. If you don't already have them, I'd replace all the springs with these newer ones that seem to be less prone to breaking

bbaggerman said:

Yesterday I had the cowl off of my RV-12 to install new exhaust pipes as per Service Bulletin 00005. I found both exhaust pipes on the left side had worked their way out and were sitting up on the muffler socket. I have attached a picture.

This RV-12 is new to me. I had some work done on it before I picked it up including new stainless steel exhaust springs installed when replacing a broken exhaust spring. That was only about 5 hours ago. Now one of the new springs has also broken and both tubes are out.

So what gives? I am wondering if this means I have excessive vibration or some other problem. Vibration doesn't seem excessive but like I said, this -12 is new to me so I don't have a lot of experience to judge by.

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When you put the new stainless springs on, did you re-coat the pipe inserts with the recommended anti-seize?

I assume there was no problem with the other original springs? Only one had broken? Did the stainless break in the same spot? Weird deal to be sure.

When seated properly with the springs set right I can't see those pipes popping out. Takes quite a bit of leverage to unspring the springs for me.

almost looks like a backfire caused this, could it be someone turned off both ignition switches off at 4000 rpm doing the ignition check then turning them both back on creating a backfire?

Hi Bob,

I have my springs packed internally with high temp RTV and safety wire run down through the middle of RTV and spring center and through the loops on both sides of the exhaust that hold the springs. Never had a spring break or come off like yours did. Knock on wood…

Bill Gardner

I had the same thing happen on my RV12is after replacing the front pair of pipes per the service bulletin. The front right pipe comes in three sections and two of the sections did not fit well I.e. they were too tight and did not insert together properly and could not rotate when inserted. This resulted in a very strained fit. Vans excellent as ever, sent me a new set and I now have no problems