Z31 Vacuum Lines
Diagrams & Replacement

This page includes lists and diagrams of vacuum lines for 86' Turbo (MT). Any differences between models should be minimal, though they will exist (especially as additional control items were added as the years went on). The diagrams should help greatly with vacuum diagnostics. I strongly suggest becoming familiar with this webpage on VACUUM DIAGNOSTICS if you have any problems.

Lengths are approximations (all rounded up to nearest inch) based on the hoses routed in my car at the time of measurement. Except for the vacuum pump lines, all the lines that were run in my Z were stock. Upon replacement, I WILL HAVE MODIFIED the length on front gallery lines and A/C lines to minimize length/cost. If you find stock lengths or your modified route lenghts to be different that I have listed, please drop me a note for comparison.

Get rid of this crap, and get this crap instead:

Pictures of silicone vacuum line will replace these pictures once done, and the exact length of those hoses will be shown.

'86 Turbo Engine Vacuum Lines (w/o A/C or Cruise shown)
note: 9/86 Turbo cars also have SURGE TANK system and vacuum lines

(if you want to buy any OEM replacement parts seen in this diagram, see FICHE DIAGRAM HERE)

To replace all the applicable engine lines below (INCLUDING all vacuum and coolant lines), you will want to order the following. Just subtract any of the noted lengths/diameters shown below from the total in the "kit" if you are not going to do that part. ALSO NOTE that these lengths are for the REROUTING that I have done on my car. For each length provided below, the hose length is slightly OVERESTIMATED, and then the total is rounded up to the nearest foot. There will be a little left over of each length. Below are the exact lengths measured out for my installation. Since you have to buy by the foot, you should end up with a few extra inches, just in case. If you want to replace the vacuum tank through firewall hose, you will need to add about 6'.

Z31 Silicone Vacuum Hose Replacement Kit
FOR 86 Turbo Manual, CA including vacuum controlled emissions devices
9/86 Turbo and Newer will have SURGE PUMP vacuum LINES.

ORDER NEEDED (for modifed lengths shown below)

116" (order 10 feet) of 3mm
165.5" (order 14 feet) of 4mm
103.5" (9 feet) of 6mm
56" (5 feet) of 10 mm

14" (2 feet) of 3/16" Clear Vinyl (HOME DEPOT)

does not include Vac Tank through Firewall hose or vacuum hoses inside car (A/C Controls)
Vac Tank about 6' from what I've read

7" of the 10mm replaces formed brake booster vacuum hose, which you may not want to do. The actual length needed to replace is more likely around 8"

Since most stores require a mininum order per hose of 10 ft you will likely have to order 10 ft of 6mm and 10 mm. I would suggest ordering 1 extra foot of each hose just in case:

EXTRA FOOT ORDER (gives you at least 1 extra foot of each hose)

11 feet of 3mm
15 feet of 4mm
10 feet of 6mm
6 feet of 10mm (may have to order 10 ft)

THE LENGTHS and DESCRIPTION of each hose is shown below


  • Installation is straight forward. Do one line at a time.

  • The stock hose clamps on the 6mm lines will not be tight on the new 6mm lines. You can either modify or replace the clamps. You might be able to get away without clamps, but I'd use them on the coolant lines.

  • On the vacuum tank, there are a couple connectors that have "guards" around the nipple. The new 3mm silicone line will not connect because the walls are too thick. You'll need to either modify the width of the hose with an exacto knife or use a small section of old hose with a barrel connector to connect the new line to the system (pictured below)

  • Be aware that silicone hose can stretch and therefore BALLOON - you may experience boost leaks if the hoses are not well secured.

  • You should not use SILICONE hose in high heat, fuel or oil transport, or off oily emissions areas like PCVs and other hoses coming off valve covers.

At Boost Controller.com (black, red, or blue only) you can get the silicone hose kit listed for $59.46 shipped, $46.01 without 10mm items. I ordered mine in the afternoon, got a ship notification the same day, and received it two days later!

If you get the $58 Hose Techniques STARTER KIT ($58 + shipping) you will end up with 8mm hose that you won't use, no 10mm hose, 3.5mm (which I have found a bit loose), and not enough of anything to get the whole job done. If you do decide to buy from Hose Techniques, it's cheaper to buy it by the foot. Since the kit lists over 10 feet per item (except 10mm) you will make out well --- just won't get the extra in the starter kit (cutters and ties). Or if you trust stuff you haven't seen, go to eBAY and get a kit that will cover you 4mm and 6mm for about $25. BE WEARY of eBAY KITS, however -- I purchased one once and instead of being silicone hose, it was VINYL. Completely falsely advertised. Make sure the packaging says SILICONE on it.

I measured the A/C control line ID @ 3mm. I bought the HT kit once many years ago and the 3.5 was a bit loose where I used it. If you do your A/C control lines and cruise line, you may want to save yourself some heartache and reroute them. Instead of running them below the vacuum canister, along the framerail, and back to the firewall, consider running them right along the top. You can use a wire loom to make it look decent. You will then have easy access to them in the future. The kit listed above uses the rerouted lengths.

There is some great information (along with detailed pictures) on vacuum lines and A/C Control Fixes:

http://users2.ev1.net/%7Ejboykin/vaclines.htm (Vacuum Lines)

http://z31.com/oboard/archives/view.pl?157 (A/C Blows Hot)

DRIVER'S SIDE FRONT AIR GALLERY (from front to back) Inner Diameter
(I.D. mm)
(1) to FPR Control Valve (bottom) 4 mm 21" 15"
(2) to FPR Control Valve (top) 4 mm 23" 15"
(3) to Manifold 6 mm 20" 19"
(4) to Throttle (right port) 4mm 13.5" 12"


NEW VACUUM LINES: RED = 3mm || BLUE = 6mm || BLACK = 3mm (AIV 4mm Lines and EGR ALSO BLACK)



(I.D. mm)
(5) to Manifold Front 4 mm 3"
(6) to FPR 4 mm 3"
(7) to Carbon Canister (bottom, left port) 6 mm 14.5"
(8) to Carbon Cansiter (top, left port) 4 mm 16.5"

NO CHANGE on FPR || Carbon Canister (OLD ABOVE || NEW BELOW)

(I.D. mm)
(9) EGR Control to EGR 4 mm 5"
(10) EGR Control Valve to Rear Gallery (pass) 4 mm 2.5"
(11) 'TEE' to Boost Sensor (see above) 3mm 7" (5" modifed)
(12) 'TEE' to AIV Control Valve (Top) (see above) 4mm 12"
(13) AIV Control Valve (Bottom) to Intake Front 4mm 13"
(14) AIV Control Valve (Middle) to AIV (see above) 4mm 5"
(15) Throttle to Rear Gallery (driver) 4mm 10.5"
(16) Manifold to 'TEE' (see above) 4mm 35" (25" modified)
(17) Intake to Carbon Canister (right port) 6mm 46" (38" modified)
(18) Headlight Motor Vent Lines (Clear Vinyl Tubing Home Depot) 3/16" 2 x 7"
(19) Vacuum Pump to Vacuum Canister 3mm ~26"
(20) Carbon Canister (middle port) to Fuel Return Hardline 6mm 9"
Intake to Vacuum Tank 3mm 46" (modified)
Cruise to Vacuum Tank 4mm 28" (modified)
A/C Heater Cock Control to Vacuum Tank 3mm 39" (modified)
Vacuum Tank to Firewall not measured ~6 feet
Passenger Side MANIFOLD Coolant Line to Rear Gallery 10mm 9"
Passenger Side COLLECTOR Coolant Line to Manifold 10mm ~5-6" (OEM is formed hose)
Throttle Coolant Line to Driver Side Gallery 10mm 7"
Throttle Coolant Line to Turbo Passage 10mm 10"
Turbo Coolant Line to Driver Side Gallery 10mm 10"
Coolant Reservoir Line to Coolant Tube 6mm 23" (could be shortened)
Manifold to Brake Booster Check Valve 10mm 3" (modified // OEM is formed hose)
Brake Boost Check Valve to Brake Booster 10mm 4" (modified // OEM is formed hose)




VACUUM TANK HOSE REROUTE in GREY wire loom (original lines go down, across bottom frame rail, then back up)