916 First Start Observations and Concerns

I started my brand-new 916 in my Kitfix for the first time the other day and I have concerns about my observations. The plane is still under construction, so the engine runs I describe below all occurred in my driveway at home. I'm posting here because I'd like to get some advice from the group.

The first few starts of the engine came as part of following the Oil Purge Service Instruction. I followed those instructions, adding oil, hand cranking w/o lower spark plugs, seeing oil pressure, seeing oil flow out the two large return lines into a catch container. With that successful, I hooked up the oil lines to the tank again, topped up the oil, and reinstalled the lower plugs. That all was fine.

With that initial (not-start-up) part of the oil purge process done, I continued with the turbo oil line purge, which requires the engine to be running (a maximum 10 second run). That went fine and oil pressure was seen quickly, then oil was seen flowing into my catch container from the turbo oil return line. It all happened within the required 10 seconds. I then hooked up the turbo oil return line to the tank and checked the oil and coolant levels, adding a little more coolant and some more oil, to get both fluids topped-up.

Just one odd thing about this very first 10-second start of the engine, was that the engine (seemingly) caught on only one cylinder initially, and it took about 6 or 7 firings of that one cylinder before the engine finally caught on the other cylinders and started to run smooth. (not sure if that is typical or not for a new engine, but I haven't seen this in any of the subsequent runs... all have caught on all cylinders right away)

With the turbo oil line purge out of the way, the rest of the Oil Purge process calls for some longer runs of a few minutes. I decided to do a few shorter 30 second runs, topping up oil and/or coolant in between, to ensure no possible long runs with low fluid levels (this is what I had heard that Dean at Lockwood was recommending for initial starts). So I did a 30 second run at 2000 rpm. The engine started and ran fine, although there was a clear odor of burning oil in the air about halfway through the 30 second run, and my safety observers reported that they were seeing blue smoke out of the stinger exhaust pipe. After this 30 second run, there was seen to be oil dripping (4 or 5 drops over a couple of minutes) from the lowest nut holding the exhaust resonator to the exhaust side of the turbo. The oil was clean and new but also had some slight milky white color (which my two very-experienced safety observers thought might be a bit of dissolved anti-seize compound that had been applied to the threads of the stud holding the resonator to the turbo). We didn't see any other drips of oil higher up on the engine anywhere... the drips seemed to be coming from some possible seepage at the interface of the resonator and turbo. A post-run check of oil and coolant levels showed the oil level to be fine and the coolant level down 1/4" from the neck, so I topped that up (I'm assuming bubbles in the coolant lines and radiator and heater core were working themselves out).

At this point I stopped my engine runs for this first day. I was concerned about the oil drips and blue smoke and I wanted to check the resonator-to-turbo nuts before running again. I did later confirm that the nuts were already torqued sufficiently per the MMH manual specs, and I carefully inspected for any more oil leaks anywhere (none seen). I also did a check of the valve clearance for the hydraulic lifters (part of the oil purge process) and I found 3 hard lifters with no "give", 4 with some movement but still within tolerances, and one that was soft and out-of-tolerance. Not a big concern yet, as I hadn't yet run the engine for the many minutes that are supposed to preceed the lifter check, but it was nice to know that most lifters were getting air purged from them already.

Two days later I started the engine again, hoping not to see any oil drips or blue smoke.

First I did a 30 second run again at 2000 rpm (to be followed by an oil and coolant level check) and the engine started and ran fine again. I didn't smell any oil burning this time (as I had during the previous 30 second run). My observer (a different observer this time) said that exhaust was visible coming out the stinger exhaust pipe (although it did not show up on the iPhone video he recorded). Since I didn't smell any burning oil this time, I wasn't too concerned. There was no oil dripping from the lowest nut of the resonator-to-turbo interface, so I hoped that things were now good.

I then did a 2 minute run at 2000 rpm. Engine started and ran fine and I again didn't notice any burning-oil odor. Instruments showed oil pressure fine at about 42 psi. Other instrumentation all indicated normal. When I stopped the engine after this 2 minute run, I could hear clicking and cracking and popping noises from the engine. When I got my head under the engine, I could see an occasional wisp of smoke rising from the turbo near where the silver (intake side) interfaces to what I think is the (brown colored) oil cooled mid-section. Also, I could occasionally here a short-lived pinging/sizzling noise seeming to come from the stinger exhaust pipe (sounded like something occasionally dripping onto something very hot and evaporating). This occasional noise was not in-sync with the occasional wisps of smoke on the outside of the turbo. After about 1 or 2 minutes, no more wisps of smoke were seen and no more popping/sizzling sounds were heard. One drop of oil was seen during this time to fall from the lowest nut at the resonator-to-turbo interface (similar to what had been seen after the run the other day) but it didn't seem to have any of the whitish coloration this time... just clean oil.

After cool-down, the oil level was seen to still be topped-up, and the coolant level was (again) seen to be down maybe 1/4" from the neck in the expansion tank, so I topped the coolant up again. I did the check of the hydraulic lifters and all eight valve lifters were now rock solid this time (I could easily press way over the required 70 Newton test force and there was no movement of the lifters).

And that is where I'm at today.

The Oil Purge Instructions call for longer runs at higher rpm, but I'm not sure I need to do that... those longer runs were supposed to preceed checking the valve clearances, but my hydraulic valves lifters are already fine so maybe I don't need to do those runs. I'd additionally like to do a longer run to get the oil up above 212 F so I don't have water in the oil. But, I'm concerned about the smoke, sizzling, and drops of oil. I don't know if these observations are normal for an initial start of a new engine (they are not mentioned in any Rotax documents that I can see).

I would appreciate any advice from you experienced Rotax folks on what I should do next.

Thanks in advance.

Glenn