Weird noise leads to low power on hills, help!

[Busy B]

Hope you guys can help me diagnose a problem with my '08 6.4l. When towing uphill with my 5th wheel the engine will start making what can be best described as a loud howl which has a lower tone than normal turbo whine. At that point I lose a lot of power. Hills with any significant incline I usually can't go over 45 without this happening. Any tips for fixing this problem would be greatly appreciated!

[CodyLX450]

Sounds like the regular cooling fan that scares a lot of people as you don't really hear it until you start towing loads up a hill.

Mine never stole power from me, but heavy loads will definitely slow your top speed down.

[H2C]

Originally Posted by Busy B

... the engine will start making what can be best described as a loud howl which has a lower tone than normal turbo whine...

I have experienced the same thing. From what I can tell the variable vane on the inlet turbo moves to a position of low or no boost.

BUSY B did you detemine what it was?

Mike

[wrench11]

This sounds like a boost leak,
check all clamps and hosses, a small black streak of soot is the sign of a leak.

If no leaks are found take the CAC to a radiator shop and have it tested, make sure they know what the leak down specs are.

[H2C]

A few addtional observations when my F250 fails to provide boost:

...it is usually when the engine is cold
...is more likely to occur when the truck has not been driven for several days
...occurs immediately after engine start
...corrects itself once the coolant temp has warmed up to approximately 120F
...you can hear the "bypass condition" slowly subside over about 5 seconds after warmed up as the variable vane opens allowing airflow into the turbo
...truck perfoms great once all the above occurs, and makes normal boost pressures up to nearly 40 psi under heavy acceleration.

Another wierd observation is these conditions do not always occur, but rather only about 70% of the time regardless of conditions. On some occasions, the truck will not have been used for 10 days, the enigne is cold, the ambient is low, but starts great and immediatley provides boost with no unusal sounds or mis-behavior.

Not sure if this is of any help but wanted to be clear on what I have experence in regard to noise and low power issues.

Mike