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Robert R
Robert R, ASE Certified Master
Category: Dodge
Satisfied Customers: 4513
Experience:  Dodge Master Certified, Dodge Sprinter Certified
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I have a 2004 dodge 2500 4x4 crue cab bed. There is a

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I have a 2004 dodge 2500 4x4 crue cab long bed.
There is a electric and vacume unit, next to the battery on the right side nex to the hood hing and fender.
It oscillates off and on every few seconds. I think it has somthing to do with the 4x4 hubs?
I could be wrong, if so can you tell me what it is and what dose it do?

Hello, welcome and thanks for asking your question. My name is*****'m a Certified Auto Technician with 29+ years experience. I will do my best to assist you. please keep in mind that I may need to ask questions of you before I can answer. When you reply please feel free to add as much detailed information as possible pertaining to your concern.

That is your vacuum pump. This unit is responsible for supplying vacuum to the items that need vacuum for normal operation such as the cruise control servo and the HVAC system.

The reason that it is cycling on and off is because there is a vacuum leak somewhere in the lines. A common area is the vacuum line that goes to the cruise control servo which is located underneath the driver side battery Follow the plastic vacuum tube under the driver battery and look for signs of corrosion from battery acid leaking onto the vacuum tube and/or rubber nipple fitting at the cruise servo. Another area of concern is where this same vacuum tube runs near the accelerator cables, many times the vacuum tube gets rubbed through due to the engine vibrations so check the complete length of the vacuum tube carefully for signs of rub-through from an adjacent component or cable.

If you have any additional questions, don't hesitate to ask..

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Customer: replied 11 months ago.
Robert, I did what you suggested and quickly found a pin hole in the vacuum plastic line next to the accelerator cable.
I want to thank you very much if I ever have any other problems I will contact you first.
Thanks again and GOD Bless you and your family.

Cool, That is the MOST common area of rubthrough. Now to fix it you just need a 1/8" piece of rubber vacuum hose to complete the repair. Just cut the plastic tube at the rubbed through point (Pinhole) and use a 2" length of the 1/8" rubber hose to reconnect the two ends of the plastic tube together and this should complete the repair. At this point turn on the key and look for the vacuum pump to run for a bit then shut off and stay off. It should only come on as needed at this point....

Keep me posted and let me know if you have any additional questions...

Thank you,



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Customer: replied 11 months ago.
If I could give you a ten star rating . I would. You made my day. I fixed it before you got back with me.
You were fight on target.
I had gone to a dealer and they could not tell me what the ( Unit ) vacuum pump was.
They wanted me to leave it with them. I can imagine how much would have cost me.Thank you so much and GOD Bless you and your family. I gave you the (*****) 5 stars.Joseph Dubois

When you visit the dealer, the person you are in contact is the "Service Writer". Many times the writer does not know everything about the vehicle. His job is to talk to the customer and be the "Middle Man" between the mechanic and the customer. If you ever need "Quick help" with a question such as finding out what that part was, sometimes it helps to ask to speak to a technician. Some dealers allow the tech to talk directly to the customer in cases like this... It would have helped to be able to talk directly to the "Diesel Technician".

Usually a diagnostic charge at a dealer is equivalent to 1.0 hour of labor at your local rate. Some dealers offer a discounted rate for the "initial 1.0 hour diagnosis".

Thank you for the 5 star rating. I don't see it yet, let me know if you are having a hard time with the rating. If you are unable to rate, let me know and I'll submit with customer service for a "no click rating".

Thanks in advance for the rating.


Robert R and 3 other Dodge Specialists are ready to help you
Customer: replied 11 months ago.
This is the third answer I have sent to thank you. I did give you a five star rating.Joe Dubois

Thank you, ***** ***** it now.

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