I'm trying to replace all of the vacuum hoses on my 75 1.8l in the engine bay and am really struggling to get the right hoses. I ordered a kit and although I've been told numerous times by the supplier it is the correct kit, most of the sizes are way off and lengths far too short. I'm using the diagram on Pelican to make sure I'm ordering the correct sizes now, but I'm confused and haven't received responses from them or AA trying to make sure what I'm looking at is correct. Below is what I think will work and would appreciate someone confirming. These are from Pelican as I have a gift card and would like to use it there.

4mm ID - 3.5x7mm
5mm ID - 5x10mm
12mm ID - 12x19mm
14mm ID - 14x19mm

Also, any recommendation on where to source the 18mm hose for the side port of the decel valve?

Thanks in advance for any help.

I found this diagram helpful when replacing the vacuum lines on my '75 1.8, not sure if you've seen it before.



Courtesy of Jeff Bowlsby. Lots of other good notes in his tech notebook.

https://bowlsby.net/914/Classic/TechNotebook.htm

I used the AA kit as well, although it was a few years ago. I remember both having some left over lines in various sizes and missing a few. Might have had to cut a couple to size even. Sorry I don't have the engine with me otherwise I'd measure them for you.

This link on pelican also has some lengths.

https://www.pelicanparts.com/914/technical_...4_18FI_diag.htm

i found when i redid the hoses on my 74 1.8 which is mostly similar that the short hose between the aux air valve and the intake plenum might give trouble. i discovered the replacement hose (woven cloth with rubber core) was collapsing when the aux intake was open during warmup and mucking up the aux air supply. i've got to find myself a better hose. i did find my original hose in a bag i'd kept them all in. definitely was original to the car. the ID on that hose when i measure it is 14mm rather than 13mm indicated on that diagram. its possible that it was slightly enlarged at the ends from being fitted for so long. it could even be preformed, or it may simply have adopted a curve after 45 years. that hose has to do a tightish little curve in real life rather than a straight line like diagram. that curve is what induces collapse in the hose. its possibly the trickiest little hose in the whole set up. if your original hose is still good i would leave it on.

some of these hoses are indeed hard to get.
the S curve hose from the pcv valve to the air cleaner on mine was impossible to find in that diameter. it could also have been a preformed hose, not sure.
looks like a different set up for that on a 75.
fortunately that pcv valve hose was still ok on mine and sealing so i left it alone.

i also could not get a replacement green hose in small enough diam from the distributor to the throttle body. but it seems as if it was ok so we left it alone too.

there is a company in germany producing these woven hoses at the moment as an OEM supplier for audi. i am trying to remember their name. someone on this site was looking for a suitable hose to do the pcv valve hose. i posted up a link. i'll have to search back through topics and see if i can find it for you.

As a rule of thumb I suggest measuring the OD of the nipple that the hose attaches to and deduct 1 mm for the correct hose ID. This works well for the hoses around 8-12 mm ID. For hoses around 4-5 mm, subtract just 0.5 mm.

The hoses shrink to the nipples and seal well without hose clamps. If they are loose especially due to age, replace them.

the company that makes the woven (yarn braiding) hoses is Cohline.
German.
its possible you can get it through audi in north america?
i'm pretty sure that is the hose brand we received here to do all my hose.
it might be possible to get some of the diams you are after.
its a grey woven yarn hose with a rubber interior core.

they had most of what we needed apart from the PCV hose and the green dist. hose.

regarding that diagram above, all those 4 hoses and sizes listed on right at bottom of diagram are confusing when it comes to the 74 (there is a similar diagram for 74), unless they are somehow referring to an external hose diameter which is not a good way to do it. i have seen another alternative diagram (t may have been on mr. bolsby's site) that gives accurate sizes for a 74 and all are to internal diameters. that other diagram was the one i found was pretty close to what was on my car. but that doesn't help with a 75 which is slightly different with an EGR etc.

you certainly can't go wrong if you follow mr. bolsby's tip and measure each one of them. though some are difficult to get off and then get back on if you don't want to leave things disassembled while waiting to get the bits. i kind of kept mine all together until i was ready to do them all and then i did them one at a time duplicating the configuration.

You can find a suitable 22mm braided hose for the 74 here:
https://italianautoparts.com/?product=braid...e-black-22mm-id

It doesn't have the pre-formed bend of the original so I used hose clamps on either end.

thanks for that info.