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Jetranger Question...


Guest CHEVY II
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don't let the 200 hours on it fool you. if it was only in for a partial repair and not a full overhaul, the 6+7bearings may not have been touched at all and you may have build-up from the previous user (not to mention the overhaul capabilities of some companies leave a little to be desired). And Mobil II will still coke even if you religiously follow the cooldown, just not as much.

To me it sounds like coking, but as others have said, call the guys who last worked on it, let them take the liability in their hands, their names are on the paperwork.

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Chevy 11, I would agree with Perfect Track, it's been a few years and was big problem at the time, coaking.

 

I could be wrong but I think it was being caused by Mobil Jet 11 and we switched to Shell.

 

Contact any engine rep and I beleive he will tell you the same thing.

 

I beleive we were up to a three minute shutdown and rotate the blades backwords after cool down.

 

Cheers, Don

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Guest CHEVY II
I could be wrong but I think it was being caused by Mobil Jet 11 and we switched to Shell.

 

Had a lease 206 this summer using Shell Oil as opposed to the two we have using Mobil, and it suffered from N2 Lockup. The first time I ever felt it...fetched up solid when you'd try to spin the rotor backwards :shock: .

 

On the other hand, I've been familiar with these two particular 206's for longer than I care to mention and neither had the N2 lockup ever. Always Mobil Jet II and 2 min cool downs. Which is why it just doesn't seem like a possible explaination for the extra drag associated with turning the rotor backwards.

 

All things seem normal and in the green when it's spinning the other way :up:

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1) Convert to Mobil 254.

 

2) Do the blade backwards walk-around as soon as they stop. Wait longer and 'you're pissin' into the wind'........and ain't doing nothing. It's "coking" your after and trying to break-free and you're trying to get it before it hardens-up. Not ALL 206's will require it, but until you find out which ones don't.......do'em all. Mobil Jet II is the buggar in most cases, as Blackmac suggested and that's why the suggested conversion. It ain't a new problem and has been with us for eons.

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Is it worse cold or hot. Have you done a decelleration check yet. The engine manual has the info on the times. If it is stiffer hot, it could be turbine rub, you should be able to hear it. I have never seen N2 lockup with Mobil Jet 2 in the 10 years I have been using it. It cokes less than 500, but not much.

Edited by BAH
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ok, my take:

 

1) what Cap said...100 %

 

2) also, a new overhaul is a bit tight, give it another 100 hrs and follow #1 as far as turning blades back right after shut down. it might correct itself very soon...I've seen this before. it only took a few hours to correct. but if it doesn't...return to overhaul facility

 

 

but whatever the O?H shop says....do that first....

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BAH -------walking those blades backwards was once a "suggestion" at most companies. In many companies now, it is a "direct order" after each shut-down and to be done immediately after the blades stop or small minutes later. Mobil Jet II will have that affect on some engines and on others it won't so I understand "where you're comin' from". I've yet to be told why that is after all these eons and I once had many conversations with one Bob Cameron from Standard Aero about this same subject. It's my personal belief that it has a lot to do with the enviroment that the a/c is used in and shall we say "other human-induced factors". Read into that what you wish.

 

The hardening takes place AFTER shutdown when the engine cools down to a certain point. Therefore, the "decel check" is not always your saviour. I've witnessed it becoming worse as the OAT plummets downward, but that may be just coincidental.

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If this just started after somebody did some engine work I would send it back and do not wait for it to get better by itself...I have seen things like that go from bad to real bad in short order....the only time I had lockup on the turbine it would not move when hot...not cold...most things get smaller when they are cold...just go swimming in the bay,boy,and you will see things shrink....is there any metal being made on the chip plugs...a lab seal(short for labrinth) ...spelling is not my best subject...could be the problem...this is a metal on metal seal inside the turbine...these have been known to give grief and usually right after a rebuld...good luck :wacko: you could/should/may...disconnect the main driveshaft and the steel short shaft and try turning the freewheel by hand to isolate the problem...and try turning the turbine wheels by hand..ps do this when the donkey is stone cold to see if you have blade rub on the engine...you could also take the starter off and see how easy things are turning from the starter pad...this you can do hot or cold....again good luck :up:

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