Turbo Bang?

[kingkevindavid]

Hey guys, sometimes when I start the truck it sounds like a loud "bang" is coming from under the hood in the area where the turbo is. it doesn't matter if it is warm or cold outside or if the truck is cold or at operating temp. it doesn't happen all the time. It almost sounds as if the hood is being punched by someone from underneath, kind of a muffled thud. It has caused me to hit the brakes backing up thinking I hit something.
When it happens, it is only once and within 5-10 seconds of starting the truck.
The truck has just a bit under 50,000 miles. I looked at at turbo and it looks good, nothing bent or broken and the impeller has no free play. it does have one small stain on one of vanes, looks like it has been there for quite awhile.
I only tow occasionally and even when I do it is only a light motorcycle trailer.
Any help would be greatly appreciated.

 

[Zookie400]

there is a tsb i remember reading about this, my truck has done it a few times. the tsb said it was the ac system, and it was nothing to worry about. does it happen with the hvac system off?

 

[kingkevindavid]

it did it the other day with heat on, can't really remember if the heat or ac has been on everytime though. I haven't really been to worried about it because it has been doing it for so long. it has been at least 2 years that I can remember. I just figured I would check all the wisdom here for any ideas

 

[Kleetus]

Yeah, you will hear a dull thud when the compressor turns on sometimes... it has to do with the pump sucking fluid vs gas. This can also be caused by too much lube in the A/C system. My car would do it when it had too much gas and was hot outside.

Has your a/c been serviced lately? You could test it by before starting the truck up, turning the heater to off, then starting the truck. Shouldn't do it. Then put the a/c to on in the max a/c and it should do it in a couple of seconds. Probably the reason it only does it on startup, is the lube most likely settles somewhere, and when the pump is commanded on, it's all sitting there waiting for the pump to take a bite.

If that is what you are experiencing, you should get that looked at before you wipe out a belt, or worse yet the seals in the a/c pump. should be an easy fix though.

 

[kingkevindavid]

thanks kleetus, that sounds alot like what is going on. I haven't needed to service the AC at all and I bought the truck new.
anyone know if this would be under the warranty?

 

[Zookie400]

there is a ford tsb, there may be a customer satisfaction type recall. its been a long time since i worked there, and i was only there for 2 months so i dont remember much about what the tsb said, i just know it exists. i would ask them, you may be lucky!