Where do I find ID specs of fuel and vacuum lines?

I have a 2001 Jetta 1.9L ALH TDI.
My repair manual and my dealer cannot tell me what ID my fuel lines are. I'm specifically looking to replace my FUEL RETURN LINES. I can guess at size but I would think the specs would be listed SOMEWHERE. Plus the dealer and local auto parts stores don't have fuel line that looks as small as my fuel return lines.

Can someone please tell me where this information can be found?
OR
Tell me the size fuel line I need for the return lines?
AND/OR
Tell me where I can purchase them at?

Am I right assuming they need to be Fuel Lines, and cannot use vacuum lines due to the heat in the area?

Thanks everyone!

the fuel lines from all the injectors to the IP are 3mm, the vacuum lines are 3mm, 3.5mm, and 4mm, upgrade to high quality silicone lines for these, no amount of heat, fuel, oil or cleaner can damage them, well im sure thats not true, but under your hood they will last MUCH longer than the stock braided rubber lines.
here is a link to the ones i use.
https://www.amazon.com/gp/product/B009PYE0W6/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

I got some in 3/8 for the fuel lines from the filter too, 30K miles and they are as good as the day i put them on, no swelling, rotting, cracks, very flexible, and i beat the crap out of mine and have much harsher and hotter temps under the hood than you ever will. they are ultra thick and will never collapse under vacuum. They get a bit darker due to oil vapors and what not over time but still look awesome under the hood.
I use them for ALL my lines now on all boost and fuel lines on my AHU, all my vac lines on my Ford escape, and my chevy g30hd, washer fluid lines too, its by far the BEST lines you can buy. i would not sue them on gas fuel lines, i tried it, put a sample in a jar of gasoline, after a month it was swollen, but not on race fuel, only that crap with ethanol

Mongler98 said:

the fuel lines from all the injectors to the IP are 3mm, the vacuum lines are 3mm, 3.5mm, and 4mm, upgrade to high quality silicone lines for these, no amount of heat, fuel, oil or cleaner can damage them, well im sure thats not true, but under your hood they will last MUCH longer than the stock braided rubber lines.
here is a link to the ones i use.
https://www.amazon.com/gp/product/B009PYE0W6/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

I got some in 3/8 for the fuel lines from the filter too, 30K miles and they are as good as the day i put them on, no swelling, rotting, cracks, very flexible, and i beat the crap out of mine and have much harsher and hotter temps under the hood than you ever will. they are ultra thick and will never collapse under vacuum. They get a bit darker due to oil vapors and what not over time but still look awesome under the hood.
I use them for ALL my lines now on all boost and fuel lines on my AHU, all my vac lines on my Ford escape, and my chevy g30hd, washer fluid lines too, its by far the BEST lines you can buy. i would not sue them on gas fuel lines, i tried it, put a sample in a jar of gasoline, after a month it was swollen, but not on race fuel, only that crap with ethanol

Click to expand...

Thanks. So let me verify...is the 3/8 for the line from filter to IP AND from IP to filter? Cause I wanted to replace that pair (the short rubber pieces are showing external cracks) but dealer wants $135 for the pair! I know online may be cheaper, but that would still be a lot of money for a couple short lengths. Though it is nice to have the clear line to see if there's any air bubbles.

THANKS for the link!

Mongler98 said:

the fuel lines from all the injectors to the IP are 3mm, the vacuum lines are 3mm, 3.5mm, and 4mm, upgrade to high quality silicone lines for these, no amount of heat, fuel, oil or cleaner can damage them, well im sure thats not true, but under your hood they will last MUCH longer than the stock braided rubber lines.
here is a link to the ones i use.
https://www.amazon.com/gp/product/B009PYE0W6/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

I got some in 3/8 for the fuel lines from the filter too, 30K miles and they are as good as the day i put them on, no swelling, rotting, cracks, very flexible, and i beat the crap out of mine and have much harsher and hotter temps under the hood than you ever will. they are ultra thick and will never collapse under vacuum. They get a bit darker due to oil vapors and what not over time but still look awesome under the hood.
I use them for ALL my lines now on all boost and fuel lines on my AHU, all my vac lines on my Ford escape, and my chevy g30hd, washer fluid lines too, its by far the BEST lines you can buy. i would not sue them on gas fuel lines, i tried it, put a sample in a jar of gasoline, after a month it was swollen, but not on race fuel, only that crap with ethanol

Click to expand...

So I held up a 3mm vacuum line to the fuel return line I pulled off AND cut to see size where it wasn't expanded from being on the nipple.
My return line looks bigger than the 3mm. It looks the same as a 5/32 (3.97mm) vacuum line I have. Is that a difference from and AHU to an ALH? Or perhaps my lines were changed out before I got it and too large an ID was put on and I need to go back to 3mm (about 1/8")?

While looking for something else I stumbled on this, which I couldn't find with a search. This answers some of my questions...
http://forums.tdiclub.com/showpost.php?p=1566427&postcount=19

Verbiage pasted here:

"Guys, I know this is not a how-to. Just stashing it here so it is easy to find.
Silicone hose sizes/lengths for the A3/A4/B4 cars.
Viton tubing for the fuel return lines.
mcmaster .com

Ft. 5041K22 Metric Silicone Rubber Tubing Firm, 3 mm Id, 8 mm Od, 2.5 mm Wall, Red (Same as 5041K52)

Ft. 5041K522 Metric Silicone Rubber Tubing Firm, 3 mm Id, 8 mm Od, 2.5 mm Wall, Blue (Same as 5041K52)

Ft. 5041K521 Metric Silicone Rubber Tubing Firm, 3 mm Id, 8 mm Od, 2.5 mm Wall, Black (Same as 5041K52)

Ft. 5054K531 Metric Silicone Rubber Tubing Soft, 4 mm Id, 8 mm Od, 2 mm Wall, Black (Same as 5054K53)

Ft. 5119K41 High Temperature VITON Rubber Tubing Firm, 1/8" Id, 1/4" Od, 1/16" Wall, Black

A3 Jetta: 3 foot of blue/red. 12 foot black 3mm. 5 foot black 4mm
B4 Passat: 6 foot red/blue. 15 foot black 3mm. 5 foot black 4mm
A4 B/G/J ALH: 10 foot of black 3 mm. 5 foot black 4mm.
With all these numbers, you will have some left over. Not a bad thing to have a little vacuum tube around.

VITON hose: 3 foot is more than you need. You will have some left over after replacing the injector lines and return line to the injection pump.

Solamia,

I recently replaced the little injector return lines with 3mm(1/8") ID hose on my car after replacing the injectors and pump at my last timing belt service, and they have been nice and secure.

I cheated and bought the hose from a local auto parts store, just specified that I wanted 1/8" ID low pressure fuel hose. It's not the cloth wrapped hose that the car originally came with, but it was available and surprisingly affordable.


That said, the IP to Filter return line is the larger size that has already been mentioned a few times, about 3/8" ID, or around 8-9mm.

Yes, filter to IP is 3/8 or 8-9mm
any section of hose will do it, dont pay more than you need, the clear section is useless, just get a ditzel mod or Nictane uber kit!

Use viton or equal, not silicone for fuel return. The factory lines are 3.5, we use 3mm. Don't forget to check/replace plug on #1.

BobnOH said:

Use viton or equal, not silicone for fuel return. The factory lines are 3.5, we use 3mm. Don't forget to check/replace plug on #1.

Click to expand...

why not silicone? like i said 30K miles and its in the same condition as it was when i put it on compared to new, other than a darker red.

I have had some cheep silicone hoses, that swelled up, cheep knock off chinesium but this stuff i linked to is epic. its on every car i have for all its lines for boost, fuel, vac, other than ethanol crap USA gas, as i said, 100 Oct race fuel does fine with it.