I recently required a 97 S-10 Blazer and the vacuum lines were a rotten mess. I found the vacuum source on the driver side of the intake which also goes to the PCV. That hose goes to the little check valve and to the vacuum ball under the hood and has a T that goes to the transfer case and 4 wheel drive. The 4 wheel drive works.... the problem is the heater is in default and only blows 1/2 defrost and 1/2 floor. I do not think I am getting any vacuum inside to the control valve. My question is where does the vacuum go into the cab? I see no vacuum source going in any where which I suspect is the problem. I think somewhere along the line that hose disappeared and I need a place to start looking. Any help would be appreciated. I did a search and figured out a lot of info but can find no mention of where the vacuum enters the cab. Thanks for the help. Pictures are always good.

 

I don't have too many great pictures, but start here and then go here. The HVAC vacuum line goes through the drivers side firewall. Before it goes through the firewall, the HVAC vacuum line tees off into a smaller diameter, hard-plastic line (black in color) before it enters the cab. In this picture, you can see the black vacuum source line if you know what you're looking at (pic is from my '04 Blazer, but should be similar to your '97. Black line is barely visible behind the silver nut-sert clip thing just above the floor vent. It is disconnected from the other black vacuum line with the long, opaque rubber junction).

 

Some very raw pics the 4x4 vacuum thread. - S-10 Forum

 

Thank you. Problem solved! I knew I had no vacuum source going into the truck as the other night when I replaced the intake manifold gaskets I traced every line and there was none going to the hvac. I looked on the drivers side firewall and there in the wires was a short black plastic tube I have been overlooking. I put vacuum to it and everything now works perfect. On a side note, last week, before I knew anything about these trucks, on my first real drive I developed a massive trans fluid leak. I got home and put it up on the lift and it was leaking above the adapter between the trans and transfer case.... where it can't leak.. I pulled the transfer case to check the fluid on a whim and , you guessed it, fluid went every where. I now know why it was 3 quarts on tranny fluid when I got it. To make a long familiar story short, I pulled the transfer case and replaced the input seal hoping to solve the problem and I found the source of the leak was the vent tube off the vacuum switch had a hole worn into it before it connects into the main transfer case vent tube. Boy I have learned a lot about these trucks in the last week. Fuel pump, lock cylinder, idler arm, transfer case input seal, intake manifold, valve cover gaskets, water pump, a/c repair, hvac vacuum problems. All I left is a bunch of leaky oil cooler and oil filter lines which do not look like any fun to replace! Thanks again for the help.

 

Here you you go for when you change your oil lines. http://www.handymanlyness.com/archiv...il_cooler.html

 

Cool, that looks easy. It was the other lines that go from the corner of the block to the filter housing that look like a pain. The front diff is in the way to see how they come in and out on the block. Got any good how to's on that? Thanks for all the help. I'm liking this truck more by the minute.

 

Take truck apart. Re-assemble............