Rotax 912S Exhaust Manifold Loose. . . .

[Phil Perry]

Hi all,. . .

 

I Watched a pilot taxying out for a flight in his part owned aircraft yesterday, and called him on the radio to tell him that the engine just didn't sound. . . . Right" ( I wasn't i the tower as there was very little going on due to the strong wind, so I was out and about with a hand held radio. . . ( otherwise I wouldn't have noticed ! )

 

The young pilot had only just purchased a share in this syndicated machine, and had only a couple of hours solo in it thus far. . .

 

He returned to the parking area and left it running at idle for a short while, and I could hear a sort of faint "Ticking" sound that just shouldn't have been there.

 

Just at this moment, one of the other syndicate owners arrived and and I pointed this out to him. The engine was shut down and we found that two of the exhaust manifold nuts had come loose, and there was a stain around the loose manifold area. The nuts were torqued up later, after the engine had cooled for about 2 hours. The rest were also checked. I wonder if anyone else has had any experience with this ? the aircraft by the way ( Not that I would think this all that relevant ) was a Skyranger, about five years old.

 

I wonder if anyone else has had any experiences with loose nuts ? ( no comic answers please )

 

Phil

 

 

[Guest Maj Millard]

The nuts are steel high temp self-locking, but will back off if not checked occasionally during normal maintenance. You must be very carefull not to do them up too much also, as there must be a gap between the steel pipe retainer, and the alum on the cylinder-head. If the steel bracket is in contact, it can over time, rub through the thin wall of the water jacket, and you will have a coolant leak. I check mine whenever I have the top cowl off, either visually or with a 13mil open-ended spanner. Additionally I'll put some silver anti-seize paste on the pipes themselve where the go into the cylinder-head. I tend not to do the nuts up too tight anymore and the whole system seems to be a bit happier with a little bit of movement......Just keep an eye on them .......................................................Maj...

 

 

[Phil Perry]

The nuts are steel high temp self-locking, but will back off if not checked occasionally during normal maintenance. You must be very carefull not to do them up too much also, as there must be a gap between the steel pipe retainer, and the alum on the cylinder-head. If the steel bracket is in contact, it can over time, rub through the thin wall of the water jacket, and you will have a coolant leak. I check mine whenever I have the top cowl off, either visually or with a 13mil open-ended spanner. Additionally I'll put some silver anti-seize paste on the pipes themselve where the go into the cylinder-head. I tend not to do the nuts up too tight anymore and the whole system seems to be a bit happier with a little bit of movement......Just keep an eye on them .......................................................Maj...

Thanks Maj, I've passed that advice on to all the guys on site with 912s engines.

 

Phil

 

 

[Sapphire]

I had a manifold hose clamp come off a pusher. Couldn't hear a thing but all on the ground said the engine was falling apart.

 

 

[Phil Perry]

Thanks Maj, I've passed that advice on to all the guys on site with 912s engines.

Phil

Just a quick thought on the 912S exhaust manifiold bolts Maj. . . . . . . Are there any particular recommended torque settings for "Maintenance" checking of these bolts, . . .? I I don't own a 912s ) the reason I ask is that when I assisted in the rebuild of an engine in a fairly old Rolls Royce silver shadow, . . . I rang the factory ( bear in mind this was quite a while ago ! ) and asked what torque setting ought to be used on the head bolts, and the engineer guy told me to use a "Ten inch tommy bar,. . . .and apply "ADEQUATE PRESSURE" on the bar to tighten the bolts ( ! ) In my lifetime involved in various engineering projects, One man's "adequate" can often be another man's " GEEEZ MATE. . . . , FOR CHRIST'S SAKE, - whaddyer tryin to do ? Bust the bolt ? ? ? ? ? ?

 

Phil

 

 

[Guest Maj Millard]

Phil, a quick look in the 912 illustrated parts listing don't show a part number for those nuts , however the recommended torque for metric nuts is below, (from Rotax illustrated parts catolog page 34-1)

 

M4: 4 NM

 

M5: 6 NM

 

M6: 10 NM

 

M8: 24NM

 

M10: 35 NM

 

It would be hard to set any torque on them anyway as you need to stop when the required gap is present between the steel bracket and the alum head (water jacket) how could you possibly get a torque on that anyway ???.....in the shop I work at we use elbow clicks to set torque ..one, two or three cracks !!!!...this is often supplimented with the TAR method of tightening (that's about right !).

 

Hope this helps ..........................................................Maj...

 

 

[bexrbetter]

Use some Loctite Red 620 on them.

 

Even Blue will work if that's all you have.

 

 

[Phil Perry]

Phil, a quick look in the 912 illustrated parts listing don't show a part number for those nuts , however the recommended torque for metric nuts is below, (from Rotax illustrated parts catolog page 34-1)

 

M4: 4 NM

 

M5: 6 NM

 

M6: 10 NM

 

M8: 24NM

 

M10: 35 NM

 

It would be hard to set any torque on them anyway as you need to stop when the required gap is present between the steel bracket and the alum head (water jacket) how could you possibly get a torque on that anyway ???.....in the shop I work at we use elbow clicks to set torque ..one, two or three cracks !!!!...this is often supplimented with the TAR method of tightening (that's about right !).

 

Hope this helps ..........................................................Maj...

Hell Maj. . . . . . . . . that sounds as good as what the guy from Rolls Royce told me about the old silver shadow head bolts ! ! ! ! My mates at 3 airfields think you are great with all your helpful ROTAX suggestions ( ! ) they want a picture of you to place on the wall of honour. . . . . .( ! ) You ought to set up a website and charge fifty bucks per segment of advice. . . .?

 

Mind You. . . since it's been 30 years since I have graced your shores with my effusive presence,. . . . I dunno how far fifty bucks would go towards a smorgasbord dinner and a couple of three schooners in the local hotel nowadays. . . . . . .

 

Phil