I have two vacuum leaks somewhere. One of them I have had since I got the truck. It always caused my heating/air fan output to switch from any output selection to the window defrost under moderate acceleration. I have no idea where that one is. The other I broke the other day which caused my heating/air to run out the window defrost no matter what output it was on, I know exactly where that break is. My question is if anybody knows a way to find the other vacuum leak or break. I have no idea where it is and have no idea how I could find it.

 

Get a hand held vacuum pump from the auto parts store. MityVac (or something like that). The vents changing position under acceleration is most likely a bad check valve.

Good luck with your ride.

 

The old fashioned way was to take an unlit propane torch
and slowly move the nozzle with the unburnt gas coming out
over all potential vacuum leak spots. When the gas is pulled
in by the vacuum leak you will hear the engine rpm briefly jump.

The new way to find leaks is with an ultrasonic probe
like the UE

http://www.uesystems.com/

that hears the distinctive noise of a gas
going inward and approaching the speed of sound

 

dieseldemon, do you know where the check valve would be located? mine has had this problem for a few years now and i just never cared about it, i'm going to be selling the truck soon though and i like to sell it in good order

 

Hold on while I guess your year and model......lol





[IMG]local://upfiles/12792/B66825950D934DACB572343D2CA139DC.jpg[/IMG]

 

sorry, 99 1500 318 4x4 standard transmission extended cab short box if that all makes any difference

 

I am pretty sure that you have 2 or 3check valves to be concerned with. The first one is connected to the brake vacuum booster. The second valve may be somewhere near the intake where the main vacuum lines connects. There should also be one more check valve in the vicinity of the brake booster. It will be the hard line that passes thru the firewall for your vent control.

Autozone, Advance, etc, all carry check valves.


Here are the two styles and what they look like. The in-line valve may be all black instead of half white half black.

Change both of these valves and see if things improve. It the easiest, and cheapest part of the diagnosis....lol






Good luck with your ride.

[IMG]local://upfiles/12792/A11743114D2A4B5A97036B29DE4C267F.jpg[/IMG]

[IMG]local://upfiles/12792/A8F6F2032B0E4DAB83DE1216149ED4C8.jpg[/IMG]

 

if youdont have the aformentioned propane torch, you can use almost any areosol can that has "flammable" on the label. WD-40 works well.

 

an old post from year 2000 that might be of interest:
----
I had ordered a replacement part from Dodge that is supposed to correct the
'Wild Vents' problem. This is where AC/Heat air blowing out vents
mysteriously changes and comes out other vents. It is most prone to happen
when accelerating. I read that the cruise control can suddenly 'pop out' of
setting too.

I haven't had the vents change wildly like that myself, but I have had the
'Defrost' setting refuse to work, then come on suddenly 10-15 minutes later.

Chrysler's 'Fix' is replacement part number 04677204.
I think there is a TSB on this.
I had seen the description of the problem in some automotive service
magazines.
My local Dodge dealer told me they now had the part, and I went and picked it
up (plus a broken passenger side sun visor clip). Cost was $7.84


The replacement part turns out to be about the size of a 35 mm Film can and is
a small vacuum reservoir with a built in check valve.
The original part (4306923) was a tiny check valve about the size of the tip
of my thumb. These check valves are in the vacuum line connected to the
nipple just rearward of where the PCV valve hose connects on the passenger
side of the engine. Just behind this check valve the vacuum line T's off that
goes to the cruise control mounted underneath the battery.

But when I went to put it on, I found that the new part lacked the proper
rubber hose fittings to install it. The new valve 4677204 has 3/16 nipples.
The new valve comes with only one rubber reducing elbow which has a female 3/8
end, and the other end 3/16 female.

The original check valve 4306923 has 1/4 plastic nipple ends and has a 1/4
rubber female elbow on one end, and short length of 1/4 rubber hose on the
other. The new valve's 3/8 rubber elbow is wrong - too big to seal to the 1/4
nipple at the intake manifold.

I went back to the Dodge parts counter to ask for the proper rubber fitting to
make it work, but they said they didn't have them and suggested I would have
to go to a parts store. At the local Advance Auto I could not find exactly
the right fittings, but was able to put the new check valve on using slightly
smaller fittings:

Motormite Mfg. Vacu-Tite! pn 47411 rubber elbow with 9/64 and 7/32 id ends,
and Motormite Vacu-Tite pn 47411 rubber straight with 9/64 and 5/32 id ends.

Seems sloppy on Chrysler's part - but maybe later model Rams than a 1995 have
different sized vacuum hoses and manifold fittings ?

 

i just bought one of those film canister size check valves and yes the ends are the wrong size.windsheild washer hose fits over the ends as well as over the original vacumn lines.just remove the rubber elbows and slide that hose on.i found that when i installed the new check valve in the line that goes thru firewall to vacumn reservoir,my problems were over.