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914World.com _ 914World Garage _ Ljet vacuum hose

Posted by: timothy_nd28 Mar 2 2021, 04:39 PM

In the process of re-doing vacuum lines on my 1.8L Ljet. The vacuum line that has given me trouble before is the 22mm (blue in picture) which I cobbled together with less than desirable results.
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I'm toying with the idea of using a hose from most scuba setups, the BCD corrugated inflator hose. It is rubber of some type, the ID diameter appears to be very similar, and I like the idea that it looks very flexible so it can be routed to look somewhat stock vs what I had before. Question is, what is this made out of, and how will it hold up?
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Posted by: PlaysWithCars Mar 2 2021, 10:12 PM

I seriously doubt that it will be resistant to petroleum products to the degree needed given the intended and designed for use case. What's wrong with the stock hose? Is it no longer available?

Posted by: Mark Henry Mar 3 2021, 08:31 AM

22mm is same size as the big vent hose for 911.
Not cheap and only sold by the meter, but it would be correct.

BTW yes I'm a scuba diver, way back in the day I was the youngest diver (13) in my province. I had a NAUI junior licence, I had to have an adult with me to get an air fill.

Posted by: bdstone914 Mar 3 2021, 08:53 AM

Just get the right hose. I doubt the scuba hose is rated for engine compartment temps.

Posted by: timothy_nd28 Mar 3 2021, 09:49 AM

Bruce, the correct hose is preformed with somewhat tight radius bends and NLA. Using a straight 22mm hose section and trying to manipulate the routing will cause or has caused in my previous experience a kink with thinner wall rubber hose or stress on the connectors on the intake rubber boot if you use thicker wall vacuum rated rubber hose. My final result years ago was adding some barbed 7/8” 90’s to get this big 22mm pipe to do what it needs to go without adding crazy stress point on the intake boot, looked like but it worked and was vacuum tight.

I like to explore a better way of doing this till 914rubber starts to reproduce these formed hoses. I have been looking at some flexible 22mm silicone hose, but somewhat worried of it collapsing at 20” of vacuum. This scuba rubber hose looks promising, appears to be super bendy and has reinforced ribs to possibly withstand a moderate burst of vacuum. I think this scuba hose is made from siliconized rubber, which may be the same material that 914rubber used on their newly reproduced 1.8 intake boots.
So Mark, this BCD inflator hose, just how squishy is it? Does this hose pinch easily between your fingers or does this hose resist being pinched and screams back at you that’s what I do!

Posted by: Mark Henry Mar 3 2021, 11:51 AM

Giving away one of my secrets but stick a short chunk of 1" aluminum mandrel bend into the hose. Make sure to round over the sharp ends of the tube, use lube and there's your tight bend without collapsing the hose.

Posted by: timothy_nd28 Mar 3 2021, 11:55 AM

Freakin Ingenious

Posted by: Mark Henry Mar 3 2021, 12:38 PM

On my /6, I can't remember if it a 3 or 4" radius, but it gives you an idea how it looks.

BTW if you want a full 90* bend you need like 100* because it sort of bends back a bit.

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Posted by: wonkipop Mar 5 2021, 08:12 PM

went through this a year ago.
porsche australia supplied all hoses to do fuel lines/vacuum lines for my 74 1.8 - except the pcv valve hose. they said unobtainable. even as hose.
no brand name stamped into hoses supplied as far as i remember or can see.
just came in a porsche bag.
(prices were reasonable and its almost impossible to source this yarn woven hose at retailers these days, aftermarket has seemingly gone over to nylon braided everywhere).

i did some research and came up with Cohline who are an oem supplier for Audi. they produce oil and vacuum hose. type 2620. NBR inside with yarn braiding. comes in DIN size 20 = 22mm ID 30mm OD.
has an internal reinforcing with steel wire.
as far as i can tell the original pcv valve hose is not internally reinforced.

there is another alternative they offer which is vulcanised yarn braided fuel line type 2122.
unreinforced internally according to website catalogue.
i've got a feeling this is the vacuum line hose that porsche supply - given the audi link?
problem is the nearest size in that has an ID 25mm. so would need to be clamped at connections. might be why porsche would not supply or claimed nothing at required diam.

i still run my original pcv hose. its ok/still sealing. the bends are 45 immediately after the pcv valve tube and before the plastic intake boot tube. i don't believe it was preformed but i could be wrong - it might just have taken the shape after 46 years - several other of the vacuum hoses removed have retained shape even off the car.

if its anything like the hose running from the charcoal can to the aircleaner, which is the next biggest hose on the engine, then its capable of doing the sharpish (45deg) bends, without collapsing and without stressing the connections into the pcv valve and the air intake boot. that new hose i put on to the aircleaner is very bendable without collapsing or kinking.

as an observation. all the original vacuum lines i pulled off were rigid with age.
the new stuff is extremely flexible. the original pcv valve hose is very rigid with age and it might be it gives the impression it is preformed. i don't think it was like that new.