940 Selecting vacuum hoses for longevity

One of the first things I did with my 93 940T was replace the unsightly vacuum lines. Not having any idea what I was doing, I used heater hose from AutoZone on all the connections. It didn't do so well on most of the connections. The lines on the turbo turn into plastic, and the 4mm PCV hose becomes soggy at the manifold side.
I'm sick of replacing those lines, and want to do the job correctly. I'd love to replace everything with silicone because it would look really cool, but on about half of the connections I'm afraid they'll fail the same way as the heater hose. I'm going to describe my plan here, in case I missed or have the wrong idea about something:

Silicone hose (for heat resistance):
Both 4mm hoses on the turbo
Airbox to turbo/PTC hose
Turbo to intercooler pipe hose

SAE 30R6/7 fuel line (for surviving oil and fuel vapor):
4mm FPR vacuum hose
4mm and 8mm PCV hoses
4mm and 6mm charcoal canister hoses
9mm brake booster hose (so many potential oil leaks around it to use silicone)
4mm hose on boost gauge (I wanted to use silicone but it's too thick to make it past the firewall)

Leave stock (seems to last forever):
All other intercooler connection hoses (see too much oil for silicone)
IAC hoses
3mm hose on cruise control module
PCV to PTC line
All nylon lines

I already know it isn't going to look good at all. And I'm going to make it worse by using blue silicone tubing because it's the most commonly available color.

RockAuto has some orange Gates silicone hose for about a dollar a foot, if you prefer that, but only has it in imperial sizes. Definitely keep the silicone away from heavy oil vapors, it doesn't handle them well.

Personally I just used a spool of generic vacuum line for most of my non-PCV hoses and it's all been holding up fine, plus I have another 20 feet on the spool should any of them start to look dodgy. Fuel line for the stuff that sees a lot of oil vapor is definitely a good call. Service rating for most of those is up to 100C/212F FYI.

If you buy rubber vacuum hose. Just be sure it's a thick wall type of hose. The vacuum hose they sell for a window washer pump for example is NOT ok to use on a hot turbo engine. PCV vapor rated hose is what you need for the large hose going over the valve cover. I think if you just bought high quality rubber hose it won't cost that much and it'll look just fine.

I just looked up the p/n for each hose and bought them on Skandix according to the table from Brickboard.
Skandix has some cheap no-name hoses that don't cost an arm and a leg like the OEM Volvo ones.
Maybe you can find something in the US using the p/n's.
https://www.volvoclub.org.uk/faq/EngineFuelinjection.html#VacuumHoseReplacement

Great info!

I swear I've crawled over that entire FAQ, and missed that section. Thank you!

Use silicone, and the proper OEM style spring clamps at each end. Those lines that "breath oil" won't swell up like the rubber hoses can do. I've had a full set in service since around 2013 and don't recall one failing in service. Another full set of silicone on my last SAAB 900T and likewise, no degradation of those hoses. Always use the clamps, and do NOT overclamp the silicone hose/tubing.

DET17 said:

full set

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Is this on a 7/9 Turbo? Even the 4mm silicone PCV line is OK after 7 years? I'd honestly be scared to try getting a spring clamp on that little plastic nipple. Sometimes I'm afraid it's going to break off just because I looked at it. I wish we could have a metal version of that made, but it looks like it would be hard to produce in metal.

khrrck said:

orange Gates silicone hose

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Now I wish I'd done that. It would match nicely with the coil and distributor cap. Maybe I'll do that on the next tune up and put the blue hoses somewhere else. Maybe the windshield washer system, since I need to take it apart for cleaning anyway.

I bought a few different sizes of metric vacuum hose from Bel-metric. The smallest stuff had a cloth braid on the outside, it was all very good quality.

One more question before I pull the trigger on a few yards of the orange silicone hose: does it match the Bosch ignition plastic orange as well as it does in pictures, in real life?

I've never seen it in person, so I can't comment. Just saw that it was listed for sale.

Best I can do is find a couple more pictures:

Gates website showing it in a package

Orange color on the inside of a different Gates silicone hose

An orange silicone Gates turbo hose

Rodents seem to enjoy silicone hose 10:1 over standard hose. I’m slowly switching back to rubber and cloth covered vacuum hoses since the squirrels are winning.

culberro said:

Rodents seem to enjoy silicone hose 10:1 over standard hose. I’m slowly switching back to rubber and cloth covered vacuum hoses since the squirrels are winning.

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Exactly. Also, the silicone hose without cords is quite flimsy, very easy to rip.
Switching back to rubber/cloth covered vacuum hoses as well.
Just be careful that those can't be stretched if the size is off.. They'll tear in short order.
Proper size, not undersized and a good ABA band style hose clamp works like a charm. And to stop squirrels, now using the spiral cable wrap, seems to work.

Silicone or good quality rubber (that seem to be hard to find) both work. I replaced the hoses to the charcoal canister with new rubber ones 10 years ago and they are fine. Replaced the same on my brothers car about a year ago and it's already cracking... Did some of the small vacuum lines on my car maybe 5 years ago and they also cracked in a short time. I then replaced all of the small ones with 4mm black silicone after that and they have been fine.

I found out that NAPA also sells the orange hose, so I could just bring in an old distributor cap and see if it matches.
Good thread. Lots to think about.

iamrolling said:

I found out that NAPA also sells the orange hose, so I could just bring in an old distributor cap and see if it matches.
Good thread. Lots to think about.

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Orange is the new black.