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DGP

407 Oil Cooler Shaft Bearings

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Hazy...this machine has never been hardlanded...very rarely has anything on the hook and there is nothing broken or cracked...we also check the bearings with a thermal gauge from time to time as we do with all the hangar bearings to see the running temps...the main problem is the grease getting thrown out of the bearing...gets all over the squirrel cage...dirt then collects...balance goes for the s!*ts and vibs start and this is leading to bearing wear...as mentioned I have replaced the shaft twice due to corrosion...this is our 3 shaft and 4th set of bearings...if you ever seen the balance procedure you would give your head a shake...1 thin washer and the balance is screwed...what do you think grease and dirt will do in short order...poor set up imho :P

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Is ASB407-02-54 incorporated? This introduced the 2 scoops on the engine doors and air shields on the bearings, P/N 407-040-328-101. This is to improve cooling and the shields are to prevent grease being blown out of the bearings. I just change a set on one of our 407's, the bearings have been there since installation of this ASB, over 1000 hrs,

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How about crappy bearings? I now our component shop guys are always complaining about the poor quality of brand new bearings (of all kinds) they are getting from Bell. They are often returning 50% of new bearings for warranty return.

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Just heard the oil cooler bearing change did not fix the problem....I already told them that I thought the mast cons had shifted...they will be conferring with bell tomorrow...I need some sleep...will be flying to the good old USA in the morning...did I tell anyone that i am looking for a job...pilot /eng :D ..36 years experience :lol:

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Check your tail rotor servo. We had one go here, bad servo valve. Caused vibs and noises from the hatrack area.

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They seem to think it is the hydraulic pump...ran it without the pump turning and all bad noises and vibes stopped...will see friday when new pump is installed :rolleyes:

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Very well could be, Doug. On my course in FT Worth a couple of years ago, they mentioned that they were "ratchety and noisy." Keep us posted.

 

R...

 

They seem to think it is the hydraulic pump...ran it without the pump turning and all bad noises and vibes stopped...will see friday when new pump is installed :rolleyes:

 

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I am serious about the t/r servo. The guys here thought it was the pump too, similar symptoms you describe including turning off the hydraulics and it stopped. they changed the pump to no avail. When they checked the servo the pilot valve was chattering away. Servo changed, vib's gone.

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I'm not sure what Doug's problem will end up being, but I'll certainly keep this in mind. These little known problems are why we have these posts me thinks.

 

On a side note, how are you guys doing with rear firewall cracks? Boy does it oil can with those big scoops on the side!

 

R...

 

I am serious about the t/r servo. The guys here thought it was the pump too, similar symptoms you describe including turning off the hydraulics and it stopped. they changed the pump to no avail. When they checked the servo the pilot valve was chattering away. Servo changed, vib's gone.

 

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