Hard vacuum lines 1998 Volvo S70 T5 Topic is solved

lionblaze55 · Post by **lionblaze55** » 06 May 2025, 09:18

Hi everyone! I have been lurking on this wonderful site for years. I am currently in the process of Stage Zeroing my daily driver aqua green T5 auto. Most of the rubber lines in this car were shot when I bought it, and I bought two kits of silicone lines, one rated for coolant and one for vacuum/air needs. I plumbed everything on the fly, running hoses from end to end without checking diagrams besides removing the SAS system and doing the ECU mod for that. My issue is that I pulled out the hard plastic lines when I did the vacuum lines, and now I am experiencing (maybe?) a slight power loss because of it. I think my silicone lines may be getting sucked shut on hard pulls and not allowing enough flow. I have no idea where these hard lines originally were in the engine bay at this point. Lesson learned, take pictures next time! Is there any good pictures anyone has that display where these lines should be running? I was looking for diagrams but they don't do a great job displaying routing/which lines are rubber vs plastic. Thanks in advance, you guys have kept me sane and saved this car time and time again!

Post by **volvolugnut** » 06 May 2025, 09:26

Test your theory by taking a length of the silicone hose, capping one end and attach a hand vacuum pump to the other end. Pull vacuum on the tube and see if it collapses. Note the level of vacuum at partial collapse and compare to the engine vacuum during a hard pull.
Others will need to provide routing photos.
I have not seen extended use of silicone hose for vacuum lines in production engine systems. They are typically only used for short connectors.
volvolugnut

Post by **abscate** » 06 May 2025, 10:00

You won’t lose power from collapsed lines. The turbo lines are under pressure, the SAS and purge lines won’t cause power loss.

lionblaze55 · Post by **lionblaze55** » 06 May 2025, 11:16

abscate wrote: ↑06 May 2025, 10:00 You won’t lose power from collapsed lines. The turbo lines are under pressure, the SAS and purge lines won’t cause power loss.

I think I need to go and plumb in my boost gauge before worrying about my hoses then. Thanks!