I have a '01 Expy 4.6. This morning, I took out the battery so I could check for leaks in the black vacuum line that runs behind it. The vacuum line is plugged into some box that's attached to the battery cover. What the heck is this "box" used for? When I unplugged the vacuum line from it, it sounded like it relieved the pressure. Also, I sucked on the line to see if it held pressure and it does. Next, I tried blowing into the line. At first I couldn't but a second later it I was able to. It felt like something was temporarily blocking the line. I suspect that there is a check valve on this vacuum line because it holds vacuum but not pressure when you blow through. Anyone have any ideas? Any help is much appreciated.


Thanks,

Anthony

 

Could the box be part of the charcoal canister system. Most emmission systems still use one?

 

I don't think it has anything to do with the charcoal canister. I'm pretty sure the charcoal canisters in my truck is located next to the fuel tank, not in the engine compartment.

 

I take it yours is a 4x4. If you mean #6 in the picture below it is an aux vacuum tank. If you turn your key to on with the engine off there will be no vacuum produced by the engine. This tank will allow you to engage or disengage the front axle with the engine off.

JMC

 

JMC,

I have heard even the Lightnings have this box, so if that is what it is, why do the Lightnings have it?

 

I am afraid that it is a poor diagram but #7 is the A/C vacuum reservoir tank and #8 is the Engine vacuum reservoir. The L doesn't have a #6. Sorry about the confusion
JMC

This pic is of the Engine vacuum reservoir. It is behind the fender on the passenger side.




This pic is of the A/C and Aux. vacuum reservoire. The top reservoir is the A/C vacuum reservoire and the bottom is the aux. I beleive that only the 4x4s have the bottom one.

 

Ah ok, that is clearer, thanks.

 

My truck is a 2wd. The second picture is exactly correct. It is the A/C vacuum resevoir. Thanks for the invo. I guess this allows you to operate the a/c controls with the vehicle off?? Anyhow, thanks for the help JMC!

Anthony