Recently one of the vacuum elbows had to be replaced. It had torn. I replaced it and again it has done the same thing. I was given a 1/8" x 5/32" vacuum elbow both times. Is this the correct size? What is the proper way of putting it on. I did as I was instructed. Or could there be another reason for the elbows blowing out?
You didn't say how long it took for the second one to fail. Was it a few minutes, a week, or a couple of months? If it happens right away, suspect a backfire. You also didn't say what it goes to. If it's something like the PCV valve, the elbow has to withstand petroleum products. If it's made of the wrong material it could soften or deteriorate. Check if either of them are soft and mushy.
If you have an automatic transmission and this elbow is in the vacuum line going to a vacuum modulator, check if that unit is leaking transmission fluid. That will destroy vacuum hoses and caps.
You didn't say how these failed either. Could you have been given an old one that was dry-rotted, and the same thing happened to the original one? If that is the case, just pop another one on.