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furgo Tue Jun 13, 2017 4:09 am

After seeing that some of the short braided vacuum hose pieces that act as connectors between tees or nipples and the longer vacuum hoses are rigid and with cracks, I'm in the process of replacing them.



• Connectors: short hose connectors, part # N 020 291 1, 3.5x1x40 mm, braided rubber hose, NLA. Alternative: N 0203122, 4x1.75 rubber hose.
• Manifold vacuum circuit: white vacuum tubing, part # 7M0955961B, 5x1 mm (6 m reel), hard PA 6 nylon, NLA. Alternative: part # 867 955 961 A, same but 5.6 m reel.
• Ported vacuum circuit: transparent vacuum tubing, part # N 0201391, 4x1 mm (5 m reel)

I've found the right 3.5mm diameter hose for the connectors, but I'm wondering about the longer, hard plastic hoses that carry the vacuum from part to part (blue/green in the diagram).

• Do these commonly need to be replaced? The reason I'm asking is because surprisingly mine look quite fine for being 40 years old. No cracks, seemingly not brittle, are these rather sturdy or is there something else I should check for wear?
• I've seen folks actually replacing these, but with silicon tubing instead of hard plastic (nylon). Is there an advantage to using silicon or simply the nylon ones are no longer to be found? Same gas/oil resistance? Does the less rigidity/more flexibility make a difference?

One that I'm considering to replace is the one that goes from the decel valve to the fuel pressure regulator, as it seems a PO did use hard plastic tubing, but with half the length of the original. He then used a length of fuel hose to bridge the gap to the decel valve. It won't make a difference to vacuum, but while I am at it and it's a 2 minute job, I can just as well do it and have more consistency in the vacuum line.


raygreenwood Tue Jun 13, 2017 6:46 am

The hard plastic whitish tubes are actually nylon.

As you got deeper in the emissions era.....the formulation of nylon items got corrected. Early on....1960's to about 1973.....you still saw a lot of nylon 6 (PA-6) being used. While nylon 6 had slightly better final dimensions during molding (less mold shrinkage) because it had a slightly lower melting temp....by maybe 40°......it had issues with moisture absorption and degradation.

By about 1975 or so most items that were used in hot or wet areas had been switched to nylon 66 (PA-66). This is why they tended to last longer. We still found some uses....oddly..... of nylon 6 into the 80s on items like emission tubing. These are the ones that just seem to shatter with age. So if they still see to be reasonably flexible and do not shatter when you clip an end......by all means keep using them.

As for hoses.....the original hoses for fuel vapor were at minimum....Viton lined or similar. The problem is the grade of viton. There are many grades. As fuel changed...and its not JUST ethanol but that is a big part of it.......the viton lines began to have issues especially when the vapors are combined with heat and moisture.

The common, fairly inexpensive viton formulations are horderline on exposure to ethanol.....and exposure time or burn through time ....that the viton is exposed to the vapors is a big part of it.
Even though vacuum hoses are not in contact with liquid gasoline.....they can actually have worse performance than the same hose used as a fuel line.....because gasoline/ethanol vapors condense on the inner surfaces of these hoses.....and pick up moisture from the air. Its that combination along with getting baked by heat (less cooling because there is no liquid fuel inside).

Supposedly......the newer formulations of chlorinated neoprene are the better formulation for ethanol/gasoline. I say newer formulations as previously.....25 years ago....most neoprene was borderline with normal gasoline even though its always been excellent with ethanol. And the chlorprenes have slightly lower constant temperature range than the vitons.

There are a couple of other fluorocarbon rubbers (viton is a fluoroelastomer)....that have no issue with gasoline or ethanol......but they are very expensive......enough so that for modern car manufacturing.....the OEMs just will not use them and have gone to nylon fuel lines in 90% of the whole car in the past 20 years.

I have just recently found a viton resin that would be fantastic for molding parts.....but the price is frightening.....at about $75 a pound. No issues with any fuels or alcohols, about 550°F constant, medium durometer and nearly as flexible as silicone.

So the materials are out there......but are just expensive enough that you wont see hoses made out of them except for aerospace use.

So for the moment.....probably use nylon where you can and Gates barricade hoses elsewhere. Ray

Wildthings Tue Jun 13, 2017 11:28 am

What is important is that you have the hoses connected to the right places. It is very common for the hoses to have been mis-run over the years which can cause performance issues. Everything the hoses hook up to needs to hold vacuum as well, so should to be suction tested. Check Ratwell.com for a diagram of how the hoses should be connected.

The plastic tubing is fine, the original connectors on each end of the plastic made from rubber hose where only maybe 2" long.

furgo Tue Jun 13, 2017 1:37 pm

Thanks for the replies and advice.

Yes, the hoses are all connected to the right places already. I drew my own diagram before I started checking them out. I'm also fine for the connector hoses (3.5 mm ID, 6,5mm OD, 40 mm length, part # N 020 291 1), for which I've found an equivalent source.

After Ray's post and learning that the tubing is nylon, I'm also starting to realize that it's not easy to find hard tubing for vacuum lines. Either I just can't find it or it's not very common these days, which is probably the reason why I've seen some folks to go to silicone tubing, which seems to be available in a variety of sizes and colors.

Also, good tip on checking whatever they connect to to hold vacuum. I had checked:

- the EEC valve on the filter box to be ok (pass),
- the breather box valve (pass) and
- the vacuum can on the distributor, which unfortunately doesn't hold vacuum (fail).

I've no idea when that failed, but I've got a suspicion that the vacuum can's diaphragm must have been shot even before I got the bus. It's just that no one ever noticed it, and I only recently occurred to me to check the distributor. A replacement can is on the way, though.

Also, check your distributors too! :)

Wildthings Tue Jun 13, 2017 2:11 pm

You can hit a wrecking yard and get all the plastic vacuum hose you want. A big truck shop is going to have several sizes as well.

raygreenwood Tue Jun 13, 2017 2:46 pm

furgo wrote: Thanks for the replies and advice.

Yes, the hoses are all connected to the right places already. I drew my own diagram before I started checking them out. I'm also fine for the connector hoses (3.5 mm ID, 6,5mm OD, 40 mm length, part # N 020 291 1), for which I've found an equivalent source.

After Ray's post and learning that the tubing is vinyl, I'm also starting to realize that it's not easy to find hard tubing for vacuum lines. Either I just can't find it or it's not very common these days, which is probably the reason why I've seen some folks to go to silicone tubing, which seems to be available in a variety of sizes and colors.

Also, good tip on checking whatever they connect to to hold vacuum. I had checked the EEC valve on the filter box to be ok (pass), the breather box valve (pass) and the vacuum can on the distributor, which unfortunately doesn't hold vacuum (fail). I've no idea when that failed, but I've got a suspicion that the vacuum can's diaphragm must have been shot even before I got the bus. It's just that no one ever noticed it, and I only recently occurred to me to check the distributor. A replacement can is on the way, though.

Also, check your distributors too! :)

No...just so we are clear....this particular tubing you are speaking of in this post....is NYLON....not vinyl.

The wire loom we were speaking of a couple of days ago is vinyl (the factory wire loom)...and yes....its not as prevalent as it used to be ...because for long term use it just sucks.

If you are looking for nylon tubing for emissions vacuum line hook ups like you have in this thread....its easy to find...just not always in white.

Here is an example
https://www.summitracing.com/parts/vpe-2650?seid=s...wAodGGgLZQ

Its only $5.75 for 10 feet. Its small...0.156" OD. There are many sizes out there.

This place has almost everything. I buy lots of things at US plastics mostly for work.
http://www.usplastic.com/catalog/default.aspx?catid=655

Here is metric tube....Now....its Nylon 6. But if you can deal with the fact that it will only last about 15 years :lol: ...and its cheap as dirt...its no problem.
https://www.usplastic.com/catalog/item.aspx?itemid=83903&catid=655

Or if you need colors
https://www.usplastic.com/catalog/item.aspx?itemid=24924&catid=655

The "nylotube" isslightly softer and more flexible and is either nylon 66 or nylon 612. You can tell this by the temp range, the durometer and teh low moisture absoprtion rating.


Sorry...at this place...it only comes in 100' rolls.... :lol: ...so you may want to get a group buy going...but its only .60 cents a foot.

There is tons of this tubing on Jegs and Summit of 10 foot lengths for equally cheap. Ray

Tcash Tue Jun 13, 2017 2:59 pm

You might be able to find fuel lines in that size at a small engines shop.

furgo Tue Jun 13, 2017 3:02 pm

raygreenwood wrote: No...just so we are clear....this particular tubing you are speaking of in this post....is NYLON....not vinyl.

I mistyped there, I did mean to write NYLON, sorry!

furgo Tue Jun 13, 2017 4:07 pm

Actually, it might even be easier than I thought to get the hard tubing.

The original part number was 7M0955961B (5x1x6000 mm). I believe part # 867955961A, still obtainable from VW for the Golf Mk2 is the same, just with a different length (5x1x5600 mm):

https://www.volkswagen-classic-parts.de/rohr-6aaab1.html

furgo Thu Jun 22, 2017 6:52 am

The 867 955 961 A vacuum hose arrived today, and it seems like a good fit for replacing just the bit of tubing I wanted to get back to stock. Some notes:

• It's a NOS part from VW Classic parts. Oddly enough, still available, although it was the part that got superseded by (7M0 955 961 B), which was used for the bus vacuum lines, is in turn NLA.
• ID and OD should be the same in both parts as per spec: listed as 5 mm OD, with 1 mm thickness.
• After measuring, OD seems to be 4 mm instead (on both original and new part), with 1.1 mm thickness. Shrinkage with age? Still good for 3.5 mm ID connector hoses to me.
• The material is definitely PA-6, as it's clearly stamped on the part. I wonder if the newer part (7M0 955 961 B) was PA-6/6 instead
• The color seems to be whiter than the clearer-looking lines I've got on the bus. The lines on the bus don't have any markings either. Age, heat and moisture might have played a part in removing markings and changing color.



Conclusion: I think it will be a nice and easy fit :)

From the discussion on this thread, it's become clear to me that nylon is the right thing to use for the rigid vacuum tubes.

Yet, to answer the question on silicone vs nylon (as I had seen some folks replacing original nylon hoses by silicone ones), it would appear that:

• Silicone is more temperature-resistant (-78°F .. 392°F vs. -58°F .. 230°F -nylon-)
• Yet it has only moderate solvent resistance => not very good with fuel

Given that it would seem fuel vapor can condense inside these lines, that really makes me wonder why some folks use silicone for vacuum lines at all.

For the rubber and plastic uneducated folks as myself, I found this overview quite useful (along with Ray's comments too):

http://www.dkirubber.com/materials.asp

raygreenwood Thu Jun 22, 2017 9:55 am

furgo wrote: The 867 955 961 A vacuum hose arrived today, and it seems like a good fit for replacing just the bit of tubing I wanted to get back to stock. Some notes:

• It's a NOS part from VW Classic parts. Oddly enough, still available, although it was the part that got superseded by 7M0 955 961 B, which was used for the bus vacuum lines, in turn NLA.
• ID and OD should be the same in both parts: listed as 5 mm OD, with 1 mm thickness
• After measuring, OD seems to be 4 mm instead, with 1.1 mm thickness. Shrinkage with age? Still good for 3.5 mm ID connector hoses to me.
• The material is definitely PA-6, as it's clearly stamped on the part. I wonder if the newer part (7M0 955 961 B) was PA-6/6 instead
• The color seems to be whiter than the clearer-looking lines I've got on the bus. The lines on the bus don't have any markings either. Age, heat and moisture might have played a part in removing markings and changing color.

Conclusion: I think it will be a nice and easy fit :)

From the discussion on this thread, it's become clear to me that nylon is the right thing to use for the rigid vacuum tubes.

Yet, to answer the question on silicone vs nylon (as I had seen some folks replacing original nylon hoses by silicone ones), it would appear that:

• Silicone is more temperature-resistant (-78°F .. 392°F vs. -58°F .. 230°F -nylon-)
• Yet it has only moderate solvent resistance => not very good with fuel

Given that it would seem fuel vapor can condense inside these lines, that really makes me wonder why some folks use silicone for vacuum lines at all.

For the rubber and plastic uneducated folks as myself, I found this overview quite useful (along with Ray's comments too):

http://www.dkirubber.com/materials.asp

The PA-6 should be fine...just remember that it will eventually get hard and brittle and crack.

The worst thing about PA-6 is its moisture absorption factor. Unless its constantly or frequently wet...its not an issue. An example of where these emission/vacuum lines fail a lot due to moisture absorption is especially seen in water cooled cars when the vacuum lines are run underneath fenders or on the bottom side of the engine compartment where water spray contacts them....or if you live in a rainy area and you have these vacuum lines that constantly get wet from spray through the side air vents on a bus....but they still last quite a while.

Also....I have had reason not to "fully" trust markings on some nylon products. I have found many parts over the years that are marked PA-6...simply to differentiate them for sure...from PA-12...only to speak to the manufacturer and find that really they are PA-6/6 and they just got sloppy.

The shrinkage rate will only be in the range of about 1% to maybe 1.5% at worst. So maybe .001" to .0015"....not 1mm. Its just a smaller line size.

I would use them no problem.

Silicone has high temperature....BUT...whether it works well with hydrocarbons...oils...fuels etc....will greatly depend on the formulation. There are hundreds...if not more...formulations of silicone. Some are made just for "improved" (if not perfect) exposure to hydrocarbons. A lot of the engine gasket RTV's are examples of this.

If i were going to use something "different" for vacuum line or vacuum line connection joints....I would use something like this:



This is "fluorosilicone" tubing. Its an alloy of sorts of silicone and a fluoroelastomer like Viton. Its not as high of a temperature as a pure silicone (500 F+)....but is pretty damn high like Viton (450 F)...and works with fuels and hydrocarbons.

This is most probably what people are using.


Ray

furgo Fri Jun 23, 2017 8:45 am

Perfect, thanks Ray.

While we're on the subject of materials and vacuum/air hoses, would someone know the type of hose/material to replace:

C) Decel valve to brake booster (hard tubing)
U) Air cleaner to charcoal canister (vinyl hose)

I've used the labels on Ratwell's vacuum hose page



Without previous experience, it's hard for me to judge whether they need replacement, but as I'm inspecting the intake/vacuum/evap lines, I thought I'd do the research now to see if there is anything else that needs replacing.

They are both still flexible, with no cracks, but they do feel hardened, particularly the brake booster tube. I had a massive vacuum leak due to the brake booster tube coming off a while ago, which prompted me to look at it.

On ratwell's site "vinyl hose" hints to the material of the charcoal canister tube already, but "hard tubing" for the brake booster tube is rather vague.

Here's what they look like on my bus:

Decel valve to brake booster


Air cleaner to charcoal canister


(edit: corrected swapped legend for hose pictures)

Wildthings Fri Jun 23, 2017 12:17 pm

Both hose C and U mainly handle air so so long as whatever you use can handle the heat you shout be okay. If you can bend your old hoses around and not see signs of cracking or splitting you should be okay to keep with what you have for now. PEX tubing from a hardware store might work okay for either of these giving an okay life, don't know how the available sizes would work out.

raygreenwood Fri Jun 23, 2017 12:35 pm

Yes...PEX tubing would be excellent for that. Its cross-linked polyethylene.

The decel valve hose looks to be vinyl....which is fine for that but not so good for the charcoal canister hose unless you get the right kind. Some of those clear-ish hoses were polyurethane...which works fine with gasoline fumes as long as its ester based.

The PEX or similar will work well for both. They may be slightly stiffer. Ray

furgo Fri Jun 23, 2017 1:25 pm

Thanks both. In that case, I interpret them to be ok and I'll leave them alone. But it's good to know the material to use when I do have to replace them.

Just some final notes for reference:

- While the decel valve hose (C) was mostly clean, the charcoal canister hose (U) had some condensed fluid along with a greasy/oily residue inside (the picture was after I cleaned it). It might have been a mixture of oil/fuel, I could not tell at least from the smell.

- The decel valve hose (C) still fits well (i.e. it's not loose) into the tee piece (B) to the brake booster. But it is no longer a snug fit - you can see that the diameter on the connecting tee's en increased over the years to accommodate the bigger hose. Do folks tend to clamp/tie wrap this connection to prevent vacuum leaks?

Wildthings Fri Jun 23, 2017 1:34 pm

If the fittings are snug they need to be clamped. You can also wrap some adhering silicone "rescue" tape around the fitting to tighten the hoses up a bit.

furgo Fri Jun 23, 2017 1:41 pm

Wildthings wrote: If the fittings are snug they need to be clamped. You can also wrap some adhering silicone "rescue" tape around the fitting to tighten the hoses up a bit.

Thanks. I assume you meant "if the fittings are NOT snug" there, which is the case.

I had initially thought about it the other way around: using tape around the end of the hose to make its OD just slightly bigger. But your solution is probably better, as it would tighten the whole fitting from the outside as a clamp, rather than pushing from the inside, which could end up with the tee diameter increasing even more over the years.

I wasn't sure of the standard practice for using clamps on flexible hoses without a rigid backing, which is why I was thinking about a tie wrap (or plastic clamp) as an alternative.

kooper271 Fri Jun 23, 2017 2:19 pm

I didn't have C, D, or U. For C and U I went to NAPA and got some heavy duty vacuum hose that fit. Don't know how well that will work yet.


If you want to replace your brake booster hose, air brake hose from NAPA is cheap and will work well.

Wildthings Fri Jun 23, 2017 3:33 pm

furgo wrote: Wildthings wrote: If the fittings are snug they need to be clamped. You can also wrap some adhering silicone "rescue" tape around the fitting to tighten the hoses up a bit.

Thanks. I assume you meant "if the fittings are NOT snug" there, which is the case.

I had initially thought about it the other way around: using tape around the end of the hose to make its OD just slightly bigger. But your solution is probably better, as it would tighten the whole fitting from the outside as a clamp, rather than pushing from the inside, which could end up with the tee diameter increasing even more over the years.

I wasn't sure of the standard practice for using clamps on flexible hoses without a rigid backing, which is why I was thinking about a tie wrap (or plastic clamp) as an alternative.

If you are worried about a clamp digging into the hose, cut a 5/8" wide strip out of an plastic oil bottle and wrap it around the hose. You need to leave an end gap of 1/8" or so. Now slide the clamp over the plastic strip and tighten away.

914Pie Fri Sep 08, 2017 12:42 pm

Recently, I ordered VW part 7M0955961B online from Jim Ellis Volkswagen for $14.85. The tube is 5x1x6000 mm and stamped "5x1 - PA6" (Nylon). The tube is white in color and made in Germany.

The original clear vacuum tubing from my engine compartment is stamped "DIN 73378 PA11 W" and it is discolored and brittle/cracked in some places.

http://www.jimellisvwparts.com/productSearch.aspx?searchTerm=7M0955961B



'76 914, FI 2.0 l L041 black



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