I have an 02 F350 diesel... and it seems everytime i start it something thumps under the hood..... feels like its either hitting the firewall or the floor boards.... but i never know when its going to do it... it could be 5 secs after i start it or it could be a few mins..... anyone have any ideas what it could be... i cant seem to catch it when i pop the hood and start it to find it....

 

That's a new one on me, sorry.

Adrianspeeder

 

strange problem. My guess is that it is the air conditioning pump. Possibly it is on it's way out? the clutch engages pretty firmly making an audible click.

It could also be vacuum related. Perhaps the vacuum resovoir isn't holding residual pressure and an air line is charging up and stiffening up thus hitting something under the truck. This would be vauum hub related.

Kind of a long shot.

 

yeah i guess its going to be a long shot.... i'll check everthing out.... let you know what it actually is... if i find it...

 

start truck with a/c off and see if noise is still there, there was an ssm for blend door causing a thump noise from passenger side on start up, if noise is not there with a/c off it is normal and there is no fix for it