Ok I finially need to get this fixed. I have read a few of the threads and have an idea of what the problem may be but figured I would ask anyway. I replaced the selector switch since I found oil or some sort of liquid in and on the control valve. I also found the same thing on the nipple of the vacuum ball under the hood. They haven't worked right since I got the truck, previous owner said her replaced the diverter vlave or box or something once before to fix this same problem. If I have that much oil/liquid in the vacuum line system should I relace all of the lines? Can I just clean them out?
Any ideas of what to check or change would be greatly appreciated.

Thanks everyone!

Paul

 

If you have transmission fluid in the vacuum system, the entire system needs to be flushed with a degreaser to remove the fluid. Hopefully for you it has not made its way into the HVAC system.

The fact that your HVAC system is not responding to the controls means that the supply of vacuum to it has been compromised either because a line is disconnected or because fluid has worked its way into the system.

The ultimate cause of this is not only a faulty vacuum switch on the transfer case, but also a leaking input seal on the front of the transfer case. A leaking seal will allow transmission fluid to push into the transfer case, causing an over full condition. A faulty vacuum switch on the transfer case will then allow the fluid to enter into the vacuum system causing more problems.

To see if this is the initial cause of this problem, pull the fill plug on the transfer case. If transmission fluid pours out, the input seal on the transfer case is leaking.

 

If you have the NP207 transfer case as in the first gen, it calls for transmission fluid in the transfer case (about 2 quarts) Which may be the same for 2nd gens also. It appears he just has a vacuum line cracked or leaking, but if there is fluid present, your suggestion is valid. Best thing to do is just go ahead and replace all vacuum lines since its only about 79c a foot at advance or autozone.

 

Under the hood, replacement is all fine and well. Under the dash, regular vacuum line may not fit where the lines go in all cases.

2nd gen Blazers came equiped with three main transfer cases (depending on year). NP231 (manual shift), NP233 (electric shift) and NP236 (electric shift with Auto4wd). There were a few fulltime AWD Blazers which used the early Borg Warner transfer case. The NP231 and NP233 both use regular transmission fluid.

 

That input seal was one of the first things I had to fix. A for what transfer case I have....it is a manual shifted NP231. So should I plan on replacing the vac switch on the trasfer case and then flushing the lines with something? What about the vacuum actuators under the dash and the control switch? Is there a place, other then the dealer to buy all of the hard lines that are under the dash?

Thanks guys!

Paul

Oh it's a 95

 

I would remove them one by one and flush them out with some Simple Green diluted properly. It should cut the transmission fluid while not harming the rubber/plastic.

 

What about the diphrams under the dash that open and close the air doors? Can I flush those out or should I replace them?

 

You should be able to flush them out.

 

Ok I have a new vacuum switch and control valve and plan to tear the dash apart tomorrow. Does anyone have an idea how to flush the simple green through the vac lines to clean them out? I can very well take a mouth full and blow it through. I do have a LARGE seringe thing I could maybe use or should I by one of those blow guns with the suction tube on it for cleaning out egines and such? I will try to find the blow gun and post a pic or a link to what I am talking about.

Thanks,

Paul

 

A syringe would work well.