four wheel drive wont work

my toyota four wheel drive stopped working in the hills it is an 89 with the 3.0 v6 engine. I have no vacum going to the actuator and i have traced it to the 2 solenoids and check valve and have no vacum to the check valve at all. From the check valve it goes to some saucer shaped thing that is connected to the exhaust manifold. i am not getting vacum from that thing, what is it and how do i test it?

I'm not sure what you mean, can you take a pic of the "saucer shaped thing that is connected to the exhaust manifold" ?

Thank you for your response, but i found the problem, i recently purchased this truck and the previous owner had put in a new engine and had the four wheel drive vacuum hose hooked to the AS REEDVALVE instead of a vacuum port. How i had vacuum for the 40 mins prior to it going out i have no idea but that was the problem and was able to get the hoses in the correct places for both parts. I still have to recheck all the rest of the lines to make sure that he didnt get any more crossed or hooked up wrong.

Glad you figured it out!
I had never seen a saucer shape thing part of the ADD system before ;)