I have a co-worker with a 07' 6.7 auto, he says when the truck sits for a day or so, he firsts starts the truck and around 2 to 5 seconds later he hears a loud bang from under the truck, possibly from tranny or torque convertor maybe? Sounds like something metal. Has any one else heard or had this type of noise. P.S. the air condititoner is off (dealer said a/c was on) "not the case".
thanks
jtnm

 

haha, my first thought was compressor kicking on, when my truck was still new (under 10k) and I kicked the a/c on, i thought a belt broke or something. Other than that, i have no clue.

 

I have experienced that noise with my 5.9l - I do not remember if the A/C was on or not.... I am interested if anyone else has had this, and if it is a serious concern?

 

Mine will do it as well. I have watched and it seems that for some odd reason it will ( not every time ) but cycle the a/c compressor for 2-3 seconds at startup. Haven't heard it lately, but I've been running the a/c. I think I remember seeing that as part of a flash a few years ago that the ecm will cycle the compressor for a short time to keep oil circulated and help prolong compressor life. Pop the hood and watch.

 

don't have a 6.7, but do you let the computer completely cycle or do you turn key and start up with out hesitation. just a thought,


Grant

 

Mine had the tail pipe section behind the rear axle close enough when you first started the truck with how the motor would torque over, it would hit the rear leaf spring with the tail pipe. Might be worth a check...

 

Thanks guys for all the suggestions, I have passed all these on to him. Mentioning the tail pipe problem Jeb_H had to him raised a eyebrow. He said he noticed how close the pipe is to the spring when bought the truck, he is betting that this is the case but he will verify this weekend. Again thanks guys.

 

This kind of makes sense, but you would think if this was it, it would happen right when you crank over - when the motor torques... I thought he was hearing the noise about 3-4 seconds after the motor was started, that shouldnt be a tailpipe.... About the A/C compressor - would it actually make that loud of a bang when cycled?

 

Mine clunks real loud sometimes when I first start it up with the a/c on. It's a commone issue with the new Dodges. Here's some threads about it..

https://www.dieseltruckresource.com/...ighlight=clunk

https://www.dieseltruckresource.com/...ht=a%2Fc+clunk