Thanks again Christine_208, mine is a 2000 with the 4 button, so I am guessing it should be the same as yours. I've had some issues with the HVAC doing some strange things but works correctly for the most part and the 4x4 works but had an issue this week, but I think that was because of the bitter cold. This will be the next project when it warms up or I can get it in a warm garage.

 

To RTJ49 the place where you are describing is the secondary air pump and it takes a 5/32" size vac line.

 

To All: Replacing vac lines on transfer case, I just did it. Because 3 lines goes down to a plastic piece on the transfer case with 3 spots , and they all fell behind the engine, it was a question of which line went to which part of the plastic cap. You have to cut any zip ties on the dip stick tube to allow all of the lines to be pulled up with the plastic cap that pulls off the transfer case. A little patience and pulling slowly up trying to free it from hang ups is needed. lines are 5/32" vac lines and there is a tee that splits off above the transfer case and uses a slightly larger vac line. The
lines can be replaced now knowing their length and which one goes where. One line hooks up to the tee near the brake reservoir , one goes to the vac actuator located under the battery and one has a plugged end that ends near the top of the dip stick. tube. I'm thinking again this line is the larger vac line and at the tee one part of the tee is 5/32 that plugs into the plastic piece on the transfer case. That plastic piece on the transfer case has a pin position location for where it fits on the transfer case.
That plastic cap has to be wiggled slightly and pulls up on it to get it off. Hope this
helps anyone interested.

 

Fitz,

This is great. Thanks for sharing.

Could you do one thing? Edit your post to include the year of your Blazer, type of transmission, and type of transfer case? E.g. "1999 Blazer, AT, 4-button."

Also, did you get the lengths of the hoses? If so could you add those to your post?

Nice write-up!

Christine

 

The blazer is a 2001 2dr , 4.3l , 3 button 4wd , type of trans automatic
The length of the vacuum lines I cannot say, that is why I pulled the whole
thing out . Once out you will not only know which line went where on the
plastic piece that fits on the transfer case , where each line connects under
the hood, and how each line is routed under the hood, and the length of each line.

 

I did all of my vacuum lines a couple of years ago. However, my HVAC doesn't really work at all. What I need to find is where the vacuum line is that goes into the cabin. Of course it is always dark when I get home from work so I have to wait until the weekend.

 

Another source of possible leaks that I discovered in my research is the vacuum solenoid switch into which the vacuum supply from the engine is connected.

I suspect mine has a slow leak because when I have not driven mine for a while, I'll get redirected from the defrost vents to the instrument panel vents when the engine is under load going up a hill.

On my 1999, the vacuum hose for the HVAC enters the cabin through the firewall outboard and below the power brake booster.

 

Aajohns 34 and Christine_208 :
The vac line under the hood, under the brake booster , 5/32" plugs into the hard plastic line that goes thru the fire wall . At least that is how my 2001 blazer has it. I'm guessing after it runs under the dash it is again plugged into the unit with a short 1-2" piece of vac line. I never had to look
at that end of it so far.

 

I stole this diagram off another thread on here but I don't remember who it was. It shows how the hoses run for the 4 button transmissions. The good thing about the 4 button is you can't ingest tranny fluid into your vacuum system. There is only one vacuum hose coming from the transmission and it's a vent. I spent quite a bit of time figuring this out. Most everybody has the 3 button with the vacuum switch and 3 hoses on the transfer case. That is what I had on my 2000 Sonoma too. With this diagram and your hose sizes, this should be an easy job to accomplish.

 

Where would one look for a vacuum diagram of their particular vehicle?