2nd Gen Non-Engine/Transmission think I may have a vaccum leak, any ideas

[JCyrbok]

Hey guys for the past week every time I start my truck after it has sat for a while (several hours) it sounds like the HVAC blend door slams shut (or open). Heat and cooling works through all the choices on the dial and there does not seem to be any problems when truck is running.



No sounds or whistles etc and no oil leaks from the vaccum pump.



My guess is a small crack in a line or plug somewhere along the way. Are there any places that have proven to be problems over the years that I should check first? any tricks to tracking down a leak if I can't find an obvious leak.



Anything else I should look to as the source of the clunk noise (it comes from behind the dash in the middle)?



This if for the truck in my sig line.



Thanks in advance,

J-

 

[jgillott]

There is a "T" in the main vaccum line running along the top of the firewall under the insulation blanket. It should be located directly above/behind the valve cover. I had a line split there on my former '01.

 

[DavidC]

They make a hand held vacuum tester, I have had one for years but seldom use it. It comes with hose and adapters. You basically hook it to a vacuum line pump it a few times and see if the gauge holds. If it holds all is good, if not you can trace it down to components.

Dave

 

[DavidC]

This is what it looks like. Mine was like 20. 00 20 years ago.
http://www.amazon.com/Actron-CP7830..._1?s=automotive&ie=UTF8&qid=1377045431&sr=1-1

Dave

 

[HHhuntitall]

The vacuum lines all come together and go out the firewall above the HVAC unit in the firewall, outside and above the exhaust pipe, then over the engine to the driver side where there are a couple tees. Check all those fittings, too. A leak there would allow the whole system to stabilize and lose vacuum.

 

[JCyrbok]

Copy thanks for the info guys. Ill check it out.

J-