Vacuum Failures / Replacing Flap Actuator
>Also, vacuum testing the four way off the brake booster, the line
>leading to the firewall didn't hold. I think it controls flap opening,
>will have to study that one.
The black vacuum line is the main vacuum supply to the entire climate control system. A leak anywhere in the system, will create a leak at that point. That black line goes to a manifold under the heater system, just in front of the central console. Check page 87-104 in the shop manual for a complete schematic. Again, looks more intimidating than it really is....
From there is is routed via 5 individual solenoid valves to : 1) the flap in the passenger footwell (blue hose) 2) the infamous water valve behind the firewall (white hose) 3) the windshield air flow flap (green) 4) the flow limiter flap (comb like) behing the center vent (orange) 5) the footwell air flow flap (yellow)
If you really want to isolate individual leaky components, you need to disconnect each individual line (from the individual valve) , connect to your magic vacuum pump, then check for operation AND leaks! If it doesn't hold vacuum for at least a minute...you'll have to work on that one!
When testing from inside the car, I found that the easiest way was to plug the black hose in the engine compartment, and remove the little blue plug at the end of the manifold to connect the vacuum pump. Now you are ready to check each individual component from inside the car, without having to run the engine! Check the table on page 87-106 to verify proper position of the various components
This is how I found I had TWO leaky components: the heater shut off valve and the center vent "comb" actuator. We have already covered the heater shut off But, replacing that other vacuum actuator , would normally mean you have to open the whole heater box ....OOOUCH!
Here's what I did, as a shortcut: (I assume you have removed the glove box) - Pop the lid of that center vent actuator (before you pop yours! (-: ) - remove the coil spring - pull the neoprene diaphragm and the connecting rod towards you, and lightly twist back and forth.. it will disconnect from the flap. No need to exercise too much force, you could break the plastic tag on the vent!! - replace with the new diaphragm (taken from a new actuator...)
Now, for the REAL fun: you'll have to re-connect the new rod to the flap! Remove the passenger side's vent hose (the one bringing ait to the door vents) , and looking from the passenger side windshiled pillar, you'll just barely be able to see (Blink and use your right eye only...no kidding!) the little plastic tag where the metal rod is supposed to connect. Takes some long tools to (carefully!!) push it back together (I use two 10 inch extensions, from my 3/8" socket set...worked like a charm.) You also need a really small light to see what you are doing in there (the very small Mag Lite does wonders here!) Not easy, but certainly beats taking the whole thing out of the car!!
Finally: - reinstall the spring and lid - check functin I feel lucky my windshield air control flap is ok!! (That one would require to tear half the car apart to replace!!)
928 Tips Home Greg's Home