Under the hood on the passenger side of the engine compartment there is a pump-like device. It has a hose on it the loops from top to bottom and a cable the runs to the center of the compartment and into the cab (I think) with another continuing to the driver side of the engine compartment. When I turn the key, this pump buzzes loudly for several seconds, stops and then cycles on again. It seems to be getting louder and it never cycled on and off before. What is it and why is it making this noise? I've checked the workshop manuals and can't find anything that can tell me what it is.

 

need more info, year of truck to start

 

2003 Dodge Ram 2500 with the Cummins Turbodiesel. The vibrating/buzzing thing is mounted on a bracket attached to the body on the far passenger side of the engine compartment. It's not mounted to the engine. It starts as soon as I turn the ignition key. Sometimes it runs without stopping. Sometimes is cycles on and off and sometimes it runs for a few seconds and stops. I thought the sound was the lift pump. I've had trouble with that before. But it's no where near the lift pump.

 

any chance you can post i pic, i'm having a hard time picturing what that may be

 

This is the part that's making the noise. It's right behind the battery on the passenger side.

 

we may have to wait for another 3rd gen guy to answer this, i havent delt with that little guy yet, but to me it looks like a vacuum pump, probably to control the hvac vents?

 

Thanks. Hopefully someone else will chime in with some ideas. We have had problems in the past with the air conditioning as though the doors just closed. The fan still blows but the air doesn't come out of the vents. Maybe there's a connection?

 

3rd gen guy here...

that is the Vacuum pump for the cruise control.. I think it covers the 4wd also in some cases.. with year involved also .. not to sure I know on second gen 4x4 are vacuum 4wd.. But on our third gens I dont remember..
Also your blend doors are not operated via vacuum they are electric.. And the mode door and blend door is broken its a very very common problem.. If you can't find them I have the part numbers if needed.. but they are dealer Items and will cost less then 200 in parts and if you do it yourself you have to remove the Freon 134a from the system and the antifreeze.. Also you will have to take everything out of the dash board Air bags, steering column. wire harness, radio, then you can get to the heater box and remove the heater box, take it apart and the broken doors are in side the heater box...
Very costly job though if taken anywhere. If doing the fix yourself you should expect your truck to be down for a few days... It took me 9 hours to do my blend doors over 3 days. with out adding new freon I added that a few days later...

 

and the vacuum pump may have a leak its why its making a lot of noise or is going out...

 

Thanks! Is the vacuum pump a simple swap or is there something I should be aware of when I replace it? I'll have to think twice about removing the dash....