Does the 04.5 have an electric vacuum pump?

[CBari]

I have been hearing a cycling motor sound out of my 04. 5 for awhile now. I have always assumed it was a motor on the hvac as I know I have some broken blend doors, but last night when servicing the truck I heard the noise with the hood open and I tracked it down to what looks like an electric vacuum pump behind the passenger battery. What does it control and are they known for going out or is it just a leak somewhere making it cycle almost constantly.

 

[cerberusiam]

Yes, they have a vac pump for the heater controls. I thought they were behind the drivers battery but maybe there are multiple positions depending on year.

 

[Bob4x4]

They are in fact passenger side near the firewall

 

[AH64ID]

Is 04. 5 the last year of that pump?

 

[Bob4x4]

I believe there are no 600 trucks that have them

 

[Bill Stockard]

They are in fact passenger side near the firewall

Yes, and the vacuum is used for operating the cruise control servo. The HVAC doors are operated by electric servo motors. If the vacuum pump is constantly cycling off and on, there is a leak in the vacuum line to the cruise control servo or the servo diaphragm has a leak.



Bill

 

[AH64ID]

I believe there are no 600 trucks that have them

The 04. 5 is a 600, so does it have one?

 

[Bob4x4]

I have seen combos that are not supposed to exist but who knows if the op really has a 4. 5

 

[rscurtis]

I know of one person with a "600" that has a vacuum pump. It's an '04. 5.

 

[CBari]

It is a 600 and the cruise works fine so what does that mean.

 

[cerberusiam]

The vac pump did not go away until MY 05. Yes, the 600 series trucks had them for 1/2 a year. That would make only the 600 trucks that have vac pumps.

 

[S.Morris]

Out 04. 5 has one, our 05, 04,and 03 do not. It is located on firewall behind pass side battery

 

[Lordsman]

I had a 04. 5 auto for a while. When I first got it I'd hear that electric pump cycling. Cruise control didnt work either as a vacuum line rubbed out over on the driver side of motor. I fixed that and all was well.
Maybe pressure test vacuum lines as you may have a small leak but not enough to create a cruise problem?

 

[Bob V]

I think it also matters if it is an auto or manual transmission. I believe by 2005MY all the vacuum pumps where gone

 

[Buddy's Ram]

Mine has it. I have a 04. 5 auto 2wd with the 600 engine. Mine comes on while applying the brakes and the speed drops below 20 mph. Cruise works fine.

 

[pwerwagn]

My 04. 5/600 has one as well. Passenger side. Our 03 does not.

 

[Blakers]

What requires vacuum to operate? Just the cruise control? Why does the 03 not have a vacuum pump? What changed?

 

[cerberusiam]

All 03-04 trucks with Cruise Control have a vac pump, thats the only way it operated. It was not done away with completely until MY 05.

 

[Blakers]

There is no cruise control linkage. Isn't it all controlled in the computer?

All 03-04 trucks with Cruise Control have a vac pump, thats the only way it operated. It was not done away with completely until MY 05.

 

[cerberusiam]

There is no cruise control linkage. Isn't it all controlled in the computer?

If you have cruise control there will be linkage, cable,, a speed control servo, and a vac pump. If you have speed control then I believe it is just a solenoid on the APPS, but, thats a bit unclear from the FSM and I don't have an 03 to look at.