Diagnosing a failed vacuum check valve (Express / Savanna van)
A common issue on the expressions of vana vans is your vacuum check valve now the symptoms of this going bad will be while you’re driving say you’re going up a hill you’ve got the ac or the vent set at any of your locations here once you start accelerating heavily the airflow will stop coming out of your vents and will default back to that setting right there you’ll
Start feeling it blowing down at your feet and through the defrost grills now the cause of this is all the blende doors inside your hvac system are vacuum actuated and once it loses the vacuum this is the default setting right here now another way to tell if this is bad is once you’ve shut the van off after driving it or even just letting it idle you should be able
To hear a hissing noise coming from inside the dashboard whenever you change this and on this van it’s not making that noise so this is the location of the hvac check valve you can see on the front your battery would be sitting right here and then it has the vacuum reservoir down underneath then if you trace that line back you can see that goes behind the accumulator
And your check valve is right there it’s a teed off check valve and doesn’t look too tough to get to but it’s easy to say when there’s no motor in the van i’m slowing the video down now to show where all three of the lines are going to off of the vacuum check valve right here where i’m pointing that one obviously goes to the vacuum reservoir which looking at the
Check valve right here that would be the one up on the left that goes to the back reservoir the one on the bottom goes to hvac controls inside the van and the one in my fingers is the vacuum feed line from the engines intake manifold so hopefully that helps you diagnose in this video you can see that hvac line is actually snapped but this is just a junkyard van
Once the vans running go ahead and shut it off so if your vacuum check valve is working you should have enough vacuum in the reservoir to turn this valve and hear your blend doors moving you’ll hear a little bit of a hiss come out of here as well so i’ll do that right now i just replaced vacuum check valve so this should work alright and that was it you could hear
The little bit of a history mup there and i heard down there in the floorboard you could hear one of the doors actually closing so this vacuum check valve works now if your van is only blowing out there on your feet and defrost or only defrost and you can’t get it to blow out towards your face that means that you have a vacuum leak somewhere between the engine and
Your hvac controls up here so i do need to note that i did actually replace this vacuum check valve once before with a dormant unit and i do love doormen they do a great job of bringing previously oem only parts into the aftermarket but i have been receiving a few questionable quality parts from them including this check valve it was bad right out of the box the
Engine vacuum would come in through this side and then these two go to both your vacuum reservoir vacuum ball and the other to the hvac system so you should only be able to blow in one way and then the other side should be stopped however with this one on the other side so yeah bad out of the box ac delco om was on amazon for about six bucks so i should have just
Done that to start with and you know sometimes that’s just the way to go you
Transcribed from video
Vacuum Check Valve Diagnosis / Replacement – Express Van By Van with Tim
