Vacuum Leak in the front

[bullheadbob]

I have some kind of vacuum leak under the hood (front) of our 1998 Chief
Deisel Pusher.. There is a small black box with vacuum lines attached right in front of the drivers seat (I will post a picture when it stops raining).. This box is constantly emitting noise like it is trying to switch something on or off ... Coincidentialy the dash air has stopped working?? May be related..??
Thanks for any input,
Bob

[gauto5150]

Could be a vac resevoir to operate things like your ductwork for the dash heat/ac?

[bluepill]

Possibly a vacuum pump, since diesels don't produce vacuum from the engine.

[Theberrys]

They are related. The pump your hearing is there for the dash AC. Either you have a leak in a hose or your pump is leaking. Mine runs for about as long as the "Wait to Start" light stays lit when I first turn on the key.

So look for a leak in a hose or if your lucky one that has come off it's fitting.

Dick

[garym114]

If it is controlled like others the vacuum pump will run until the vacuum reservoir has enough vacuum to operate the AC dampers. If you have a problem it will run continuously. You either have a vacuum hose that is loose or cracked or a pump problem. On one that has been around since 98 the hoses are starting to deteriorate.
It could be the vacuum pump. Find the vacuum pump and pull the suction hose and put your finger over the fitting to the pump. If it still runs and can't pull a vacuum you have a pump problem. Replace it or lubricate the valves in the pump. I used pneumatic nail gun oil two years ago on mine and it is still pulling a vacuum when it wouldn't before.
Until you get the vacuum problem fixed the AC and heater controls will not work.

[cbeierl]

I don't know if your 1998 chassis is the same, but you might check out this earlier thread (and the ones it references): Weird Buzzing Noise...????.

[garym114]

bullheadbob - What did you find?

[OldChief7155]

Check the rubber tubing up front. They dry rot. It is windshield washer tubing available at any auto parts store.

[bullheadbob]

Looks like the leaky hose is in the dash. I am in the process of tracking it down.

If I turn the temp dial up and switch the selector switch to "Defrost " the
vacuum pump stops..

I'm a slow but steady learner...I have alot of time to solve this problem.

As soon as I find the solution I will post my results.

Thanks Again For all your help.

Bullheadbob

[bullheadbob]

Have the dash apart. I don't see anything wrong in the immediate are. I have read other posts regarding the "Green" Vac Line being inserted into
the Heater core switch. I have found the green vacuum tube diving down (out of sight) to the rear of the dash Below the Windshield (center).
I dont know where it goes from that point or how to access it. Maybe I can Access it below the slide out table in front of the passenger seat?
I have pulled the vac line off the Vacuum pump and put my finger over the vac pump opening and it stops running.. so I have a vacuum leak .
..... Need some more help
Thanks,
Bob

[Sealevel Ram]

Originally Posted by bullheadbob

Have the dash apart. I don't see anything wrong in the immediate are. I have read other posts regarding the "Green" Vac Line being inserted into
the Heater core switch. I have found the green vacuum tube diving down (out of sight) to the rear of the dash Below the Windshield (center).
I dont know where it goes from that point or how to access it. Maybe I can Access it below the slide out table in front of the passenger seat?
I have pulled the vac line off the Vacuum pump and put my finger over the vac pump opening and it stops running.. so I have a vacuum leak .
..... Need some more help
Thanks,
Bob

Had the same problem this week on my MH, and the referenced threads helped me out. It was a leak in the small connector to the green tube.
Not sure about your rig, but mine was under the hood, not too far from the vacuum pump itself.
Follow the links from cbeierl and you will see some pics.
Good luck.