So I have to replace my heater core in my 97 blazer. I figured since I am going to have the whole dash out I might as well replace the vacuum lines behind the dash, I have heard all kinds of suction/hissing noises back there so I am assuming its a vacuum leak and hoses are so cheap. But I do not know the sizes I need to get. If anyone knows please let me know =) thank you very much.

 

The lines under your dash should be a harder, more robust plastic line, not the soft rubber lines typically found under the hood. They should not need to be replaced unless they are broken.

 

Agreed. If you have 4wd, and your transfer case vacuum switch has never been replaced, you may have t-case fluid in your lines, which can provide some unwanted lubrication around the line connections. Vacuum will seal less effectively at the connections, possibly causing leaks.

 

hmm well thanks for the info guys. I will have to check and see if there is fluid in the lines. The truck has 190k on it and as far as I know nothing with the vacuum system has been replaced.

 

A little tutorial on t-case fluid in the lines:

T-case vacuum switch

 

Thanks AA looks like I gonna replace the switch. Might as well it's only 25 bux

 

Don't get the Dorman... The one I got lasted less than a year.

 

ok, autozone has a few diff ones all listed for my truck. Will this one work?
Duralast/Transfer Case Switch (SW3467) | 1997 GMC Jimmy 4WD 6 Cylinders W 4.3L SFI | AutoZone.com

 

Thanks this is exactly what I needed thank you so much.