4 button Auto has limited vacuum lines, nothing like the 3 button systems Let us know when you have the vacuum pump available.

 

Just picked up the hand pump.....now i never used one of these so the best watered down instructions would be great haha

 

Here is as "watered down" as it gets:


Under the hood: Locate the hard plastic vacuum line for the HVAC that runs to the interior. It will be connected to a rubber vacuum line near the brake booster. On some vehicles the plastic line enters a wire harness and the whole thing goes to the interior. Usually those connect on the left inner fender, just rearward of the washer reservoir, then the plastic line disappears into the harness. Disconnect the rubber line from the plastic line. Connect the vacuum pump using the adapters and hose that came with it, to the plastic line. Make sure the connections do not leak. Apply ~20" of vacuum with the mode switch in each separate position, (a total of 8 positions). This will test each separate mode for leaks. Each mode must hold vacuum. When you change from one mode position to the next, vacuum may or may not drop off. If it does, pump it back up to ~20". After testing mark down the results for each mode, (holds or leaks). If a mode does not hold vacuum, that circuit will need to be traced to find the leak. Each mode has a different color vacuum line which makes troubleshooting under the dash a little easier. Colors are: Red, Blue, Yellow, Black, Brown, Grey, & Orange. Good luck, & post your questions and results.

 

just got my tools, wont be taking anything apart until atleast tmr. i did locate when the vacuum line enters the cabin. goes into the harness and up to the plastic t with 2 other lines that come off it. some were replaced a year ago including the one to the fender and idk if it was done the same way it comes stock or he did other crap because the guy wasnt the brightest to be kind

my question is while still testing under the hood.is the vehicle off for this test? and do i just take the line that goes through the firewall inside the cabin off at the T and plug it into my hand vac? also how long should vacuum pressure be held at 20ish to determine if theres no leak?

 

The vacuum pump supplies vacuum for the tests, and there is no electrical involved, so the ignition can be in the OFF position. There are 3 different sections to the vacuum system that will need to be isolated from the others and tested independently for leaks. HVAC: which includes the line under the hood to the mode switch, the mode switch itself, all 5 vacuum actuators, and the lines from the mode switch to each actuator. 4WD: Which includes the vacuum switch for the front axle actuator, vacuum line to the switch, vacuum line to the axle actuator, and the actuator itself under the battery tray. UNDERHOOD: Which includes the vacuum source, vacuum lines, vacuum Tees, check valve, and the vacuum reservoir.

The first section we'll test is HVAC. The pump connects directly to the vacuum line, (under the hood) that goes into the cabin. Each mode position: OFF, MAX AC, AC, BILEVEL, VENT, FLOOR, BLEND, & DEFROST needs to be tested separately to determine which vacuum circuits are OK, and which ones leak. Select OFF on the mode switch and apply ~20" of vacuum. Ideally each mode position should hold vacuum indefinitely, realistically it should hold for ~10 minutes. When you move to the next mode switch position, it's perfectly normal for the vacuum to drop as it is vented from the first "set" of actuators & lines, and it's applied to the next "set". At each new mode position, vacuum needs to be replenished to ~20". Some of the different modes will require substantially more pumping than others. Repeat this for each of the 8 positions and mark down your results for each one, (mode position, beginning vacuum reading, and after ~10 minutes). It might be worthwhile turning the ignition to the RUN position to make sure airflow comes out where it's supposed to in each mode position, (might help with diagnosis). Post the results and we can analyze them.

 

that hand vacuum was complete junk. it had to be leaking internally. and after the first test it got stuck at 10 even when disconnected...its in the box to go back and still stuck at 10

any better not too expensive brand i can get? mittyvac? heard up and down about them

on to the plastic line that enters the cabin. is that rubber piece that connects to the T and plastic vacuum line supposed to slide off and on? and when testing there, does the rubber sleeve i guess i can call it stay on or off?

UPDATE: re-read your previous reply and saw the rubber sleeve came off. none of the adapters that came with the one thats now broke, fit that very small plastic line, they were all too big. based on your recommendation, i wanna make sure it comes with a smaller adapter

 

I go through about 1 pump a year, but I use it a LOT. I've tried about every brand there is. The expensive ones really aren't that much better. Right now I have a Mighty Vac and it's holding up pretty well.


The Mighty Vac comes with a bunch of adapters and short pieces of rubber line. For the small plastic line, stick a rubber line over the plastic one, then use one of the cone shape adapters on the rubber line, works great. The connections all need to fit tightly so they don't leak.

 

im gonna head back to the freight when I get the chance to return this, and get the might vac they had with a 20% off...i think it was mv800 or 8000...gonna be a few days though.

 

so heres what i found, i think...

got the mityvac8000....i keep getting a drop in numbers when testing the line that enters the cabin , i tested off, max ac, ac and blend..they all had drops. i tried using the rubber piece that comes with the kit, then the piece of rubber that comes on the plastic line. felt i had a good connection but not sure, drop was slow

i did a test to make sure the vacuum hand pump isnt leaking. i took the line that goes from the T to the fender reservoir....it held at 20 for over 10 minutes....vacuum pump isnt the issue.

if it is really leaking at the plastic line running into the cabin for all modes, what would be my next step?

 

With the vacuum pump connected directly to the black hard plastic line, you are eliminating/bypassing all vacuum lines under the hood: The BLEND position is the default mode. Vacuum is applied to the mode switch, and none of the vacuum actuators have vacuum applied to them. If the vacuum decays, there are two possibilities: Either the (source) vacuum line going to the mode switch is leaking, or the mode switch itself is leaking. The easiest way to find out which one is leaking, is to remove the vacuum connector from the rear of the mode switch, cork off the black line in the connector with your finger, apply vacuum to the black line under the hood, and watch for decay. If vacuum holds, the mode switch is bad. If vacuum decays, the line is leaking. Accessing the vacuum connector on the mode switch will entail removing part of the dash.


This is only part of the HVAC & 4WD vacuum system. There may or may not be other leaks. The leaks must be located & repaired as they are found, until the system holds vacuum when you apply it at the main source line, (near the PCV valve).