All,

I've been trying to track down what may be a phantom vacuum leak. It's driving me mad.

When I applied vacuum to my hoses leading to the TAD and TAB, there was definitely a leak. I pulled the hoses and they're good. The solenoids, however, seem to leak.

I read somewhere that they're supposed to vent to the atmosphere. Is that correct? And if so, I take it they do so at a metered rate?

Also, does the EVR hold a constant vacuum, or does it normally vent? I can get an EVR at autozone, but the other two are probably dealer items.

Lastly, just out of curiosity, what to the TAD and TAB do? It seems one goes to the smog pump, but I'm at a loss.

Thanks!

 

for those that do not speak in code, what the heck are you talking about?

 

TAB= thermactor air bypass
TAD = thermactor air diverter

There's a series of three solenoids on the driver's side of my 4.9L I6. The first is the EGR vacuum solenoid. The other two are the ones mentioned above, I believe.

I'm trying to figure out if those solenoid valves should hold a vacuum

 

I know the EVR functions as a controlled leak. You need to make sure you have the vacuum supply on the correct connector:

courtesy of oldfuelinjection.com

I am not aware the TAB/TAB solenoids function in the same manner. I never tested mine because the vacuum lines running to them were already removed when I purchased my old 1992 F350.