To be honest, I don't know. I thought it might have gone to the vacuum driven ***** for the climate controls, but the one line that goes into the firewall near the heater hoses might be all the vacuum the climate control needs. So it might go to some emission control near the fuel tank? not really sure.

 

Where it disappears into the fender is just a vacuum reservior on a 1998 with CCC, don't know about other years. I just went through this mess with my 1998 on Christmas Morning.

 

Jeff,

I just reread your post. Your figure 3 and 4 don't jive. Your figure 3 is correct. If vac lines were hooked up as shown in fig 4, your front axle would not engage and your climate control would act funny during periods of low vacuum.

Just to shed some light on my recent findings:

1. The vac source should go to the BLACK side of the check valve.

2. The side directly opposite and inline with the BLACK side of the check valve goes to the vacuum reservior, which is located in the fender under the ABS stuff.

3. The small line exiting the check valve at a 90 degree angle is two fold- the larger rubber hose running towards the passenger side of the vehicle goes to the transfer case switch which controls your front axle engagement, and the hard plastic line (shown in the lower right hand portion of figure 4) goes to the climate control system.