Our cruise control on Old Blue did not work when we went on our recent 50 mile jaunt. So I checked the two things that I am qualified to check.
1. Alignment of the magnetic pickup on the drive shaft. Looked ok, no broken wires, all in accordance with mfg directions
2. Vacuum lines. Again all look ok, no leaks.
But, at the end of the vacuum line that the servo hooks into, there is a 4' vacuum hose that goes forward to an area in front of the radiator and the vacuum hose hooks into a round thing about the size of a softball. It has one small black wire coming out of it. Can anyone tell me what this softball sized thing is?
Jim

http://www.ecklerschevelle.com...ister-1968-1983.html

You ahould have two vacuum lines, one from the intake manifold and the other that connects to all your vacuum devices. This acts as a big cylinder to store vacuum (the air sucker cousin to the dark sucker). If you don't have two lines something is missing, the line to the vacuum manifold or even the line to the intake manifold.

Pressure tank, surge tank what ever you want to call it. It is just a reservoir of vacuum.

How would I know if it was leaking? We have a line going from the intake manifold to a 't'. The small leg of the 't' goes to the speed control servo. The other leg of the 't' goes to the round thing--vacuum canister. I guess if it was leaking, there would be no vacuum in the hose at all. So, start her up, take off the the 't' and see if there's vacuum? At the source of this vacuum system, there is a metal pipe coming off the same nipple on the intake manifold that goes to the automatic transmission. Has something to do with shifting I think. And what would the black wire coming off the black softball thing be for?
Thanks from the dummy

Attach a vacuum gauge to the "T", or anywhere (any chance you have a vacuum gauge in the dash?) and see if you have at least 15 psi(more correctly "inches") of vacuum. Generally a vacuum leak makes the engine run poorly, and the transmission won't downshift when you floor it. Another culprit is the vacuum manifold and tubing in the climate control including the control head, tubes and vacuum motors for the various doors in the heat and ac system. If low vacuum start by pinching off the tubes or blocking them at the intake and work your way along until vacuum drops. That is the point of failure. The canister is usually just hollow so there are no parts. Any one will do and only the mounting determines the size. Junk yards are a cheap and easy place to find one. Yours is probably on most GM cars, any year from the 60's to the late 80' or 90's.