1994 960 sedan 199K miles. I went under the hood looking for a vacuum leak because my climate control system just started switching the flow from the dash vents (which were selected) to the floor vents every time I gave it any throttle, basically any time other than idling.

Well I found the source. A hose had slipped off of a smooth nipple on one of the check valves or control valves next to the firewall. In addition I found an answer, sort of, to my earlier question below about vacuum tubing sizes. I discovered that instead of soft rubber tubing, there are hard plastic hoses which are color coded for the different vacuum circuits, with small sections of rubber tubing attached to both ends of the plastic hoses to connect the ends to nipples on vacuum ports. The rubber ends are molded or attached to the ends of the hard plastic vacuum hoses. The rubber ends look like a standard size less than 5 mm ID perhaps 3 mm ID. I suppose one could purchase soft rubber or better yet silicone vacuum tubing to replace the plastic/rubber ended vacuum lines completely. But the original hard plastic vacuum lines look very robust to me. At least mine aren't showing any signs of failure yet. With one exception I didn't even find that any of the integrated rubber tubing sections at the ends of the plastic vacuum hoses were dry rotting. But it's a different setup than I've seen on a car before, and frankly this looks more robust than rubber hoses end to end. I like the setup.

Original message FWIW:
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I want to basically replace all of the vacuum tubing under the hood/bonnet and also that feeding to the inside of the car, where vacuum is used on the climate control system, with silicone tubing.

What sizes mostly do I need? I see silicone tubing in 10 foot lengths commonly available. But before I spend between say $15 and $20 per 10 foot roll, at least one roll for each size, I want to ensure I get what I need and especially no size that I do not need.

Also did Volvo use metric size tubing and do I need that for the best fit in some cases? I know how to convert SAE/Imperial to metric and I know a few sizes that are nearly identical between the 2 systems. I just thought if someone else out there had already done this job, I would like to benefit from the time you spent figuring it all out.

 

Hey Tom I just had the pcv system serviced on my 95 960, had a very hard time with finding a home for a wayward vacuum line. I cannot for the life of me locate a diagram with pictures for the 95 and up 960. I see your in Va? Are you anyway near Va Beach? I would like to meet you and share tips

 

I am about 25 miles west of Charlottesville. I have a group of diagrams that I've been accumulating for my ''94 960, some of which are PDFs that contain diagrams for 2 ranges of model years I guess corresponding to the 2 body styles with the drivetrain and other changes that occurred from '94 to '95.

I'm out of town today but I'll check to see if I have a vacuum diagram for '95 and up model years.

 

I found the repair manual PDF that I was looking for, but it's so small it's probably of little use. I attached it to this message anyway, it's a PDF file. Also below is a picture I found when I searched for 1995-97 Volvo 960 vacuum circuits: