BLKTOPTRVL

Reading a few threads here I find that silicone has problems just as rubber does. The biggest risk seems to be splitting if the hose is nicked (From Robinette site).

The real advantage to silicone seems to be that it will hold up better over a longer period. If this is true, then it seems that using rubber and replacing it more often might be the best way to go. I say this because I am willing to bet that within 40K miles I am sure some hose, valve, or other part will need to be replaced and 'if you are already in there, you might as well replace?'

So, the questions are...

How long does rubber last as compared to silicone?

If rubber is used, how do I know what specs should be adheared to?

Is there a supplier that sells a set of rubber hoses for 3rd gens?

For those who have done the silicone replacement, I would like to hear opinions before I head for the rubber tree.

BTW - at this time the car is running silicone that was installed by the previous owner 40K miles ago, and I don't have confidence in the boost system right now - which is why I am thinking about checking all the hoses.

BLKTOPTRVL

BTW, at this time, I am running the silicone as installed by the previous owner (by Pettit) 40K miles ago. I am interestested in replacing the hoses this at this time because the turbo system has not been running at it's best for a while and it is time to lift off the UIM to take a look.

High Temp Silicone

Car manufactures are caught between making a product that is acceptable for the application, is cheap to produce and can make profits in spares sold in the parts department.

In general you can use this as a guideline. All numbers quoted here are from the U.S. Government spec "HDBK-695" for life of materials.

Shelf life-
Silicone = 20+ years
Fluroelastomers = 5-10 years
EPDM, Poly Chloroprene (neoprene), Nitrile = 3-5 years
SBR, Natural Rx, Polyisoprene = 1-3 years.

The "service" life is different than shelf due to the heat cycling, ozone and chemicals that become in contact with the hose.

IF you choose to use a organic rubber vacuum hose, the best material (Chemical and temperature resistant) is Fluroelastomers (Viton). Using Viton will set you back more than silicone but the benefits are: increased tear, tensile, elongation and fluid resistance. I didnt put temperature in there because depending on the grade of Viton, (i.e. percentage of blend EPDM) the Viton may fail at a lower temperature than silicone. There is "commercial" grades in the industry which means as long as we use 51% base material we can call it that. For example if I mix 51% viton with 49% .30/lb EPDM it is still called Viton.

Next in line for the organic materials is Acrylonitrile. Most commonly known as NBR, Buna-N or just Nitrile. This offers better fluid resistance than most other organic and silicone compounds. The limitations are that it is attacked by ozone and has a relatively mild low temp brittleness point around 0ºF

The right grade of silicone, for example Platinum Catalyzed, will yield a 50-60% increase in the physical properties over the silicone that most people are familar with. That said you still are limited with the issue of fluid resistance. Silicone has virtually zero resistance to oils and hydrocarbons. There are ways to formulate certain silicone bases to resist these elements but I dont think anybody here wants a chemistry lesson.

Therefore you choices from most expensive to least are:
Viton, Silicone, Nitrile

Best fluid resistance to least:
Viton, Nitrile, Silicone

Highest temperature resistance:
Silicone, Viton, Nitrile

Longest life:
Silicone, Viton, Nitrile

We manufacture all of the compounds listed in this reply however, I am partial to silicone over the others only because I believe it out performs the others in the vacuum hose application.

Jim

rynberg

I have lately come to my senses a little bit in regards to the whole vacuum line thing....I think rubber hoses are just fine to use. RonKMiller recommends DuroBlue (Goodyear) tubing.

My car is a 95 with 77k miles on it, the vacuum lines are mostly in good shape. I'm sure the few under the rat's nest are hard as a rock but the rest seem to be holding up ok. I don't plan on replacing them until my engine rebuild.

bond007

I pulled apart my car off-season maintenance (which is now extending to the on-season, argh) and found that some the very meticulously cut/installed Hose Techniques silcone lines (with the thick walls) from about 3 years ago/20,000 miles were starting to split at the ends. I had to cut the end off past the split so it the split wouldn't increase in size as the hose was put back on.

That said, I'd like to hear what the Viton lines look like after about the same service interval. If neither are any better, then there doesn't seem to be a "silver bullet" for this problem...

As for the "hard as rock" rubber lines, from my installation and other experiences on other cars, as long as they don't splilt/break, they seem to hold out okay. You just have to be prepared to take a peek under the plenum if you do have a boost issue...not like it is that hard [not being sarcastic, either]!

Regards,
--Ashraf

High Temp Silicone

There is no way Viton lines will split. The reason the silicone lines split is because they were exposed to either aromatic hydrocarbons or oil in the lines. Thats what happens to silicone when it is exposed to these elements. Maybe Viton is the way to go here. Maybe instead of putting so much time into running silicone, I should spend a little time making Viton vacuum lines!

dgeesaman

iTrader: (7)

I've looked in Mcmaster Carr as a starting point for Viton hose. The sizes don't line up with stock lines exactly, and it's not clear which hardness is best.

HTS, are you able to provide Viton of the appropriate size and durometer?

High Temp Silicone

We have equipment to make it in any ID from .070" to 6" ID with up to a 1" wall!

What are the standards?

3.5MM
4MM
6MM
8MM
10MM

just like the silicone?

I would stick with 70-75 duro on the lines. Viton is not cheap to make soft. In fact there are only 2 companies that can make duro <60 that I know of.

I have to mix a lot of Viton to make these kits. Is there enough interest in me doing this? I would use 100% Viton bases that meet the U.S. Government Specification Mil-R83248C Ty 2 CL 1, mainly because we use a lot of it, and secondly I want to offer only a 100% base material not a blend Viton/EPDM.

dgeesaman

iTrader: (7)

Speaking for myself, it would be great to have an all-viton hose kit similar to the silicone kits already available. These kits contain 40' @ 3.5mm, 15' @4.0 mm, 16' @ 6.0mm, and 4' at 8.0mm. With the Si priced at $120, you would get my purchase if you were under $200 or $250. Durometer should be hard enough to really discourage kinking, but not to cause people to bust solenoid nipples.

I'll bet a group buy would net you 10-20 guaranteed buyers.

I'd imagine that the viton would be only in black or whatever the natural color is, since it would really expensive for you to compete with the color variety available in silicone. I think the viton market would be racers and daily drivers for that reason.

DaveW

Another factor to consider is the wall thickness-to-diameter ratio. If the wall is too thin (i.e., a 1-mm wall on a 4-mm ID hose) it will be very prone to buckle in bends and collapse from vacuum. The thicker the wall, the less likely this is to happen.

The buckling in bends is more or less independent of hardness, but is related to bend radius, ID, and wall thickness. Collapsing on a straight run is related to wall thickness, ID, and hardness.

Anyone in the hose industry have any recommendations on this subject?

spurvo

Does 100% Viton bend easily? If not, you will really want to form some of those tight bends into the hoses, or risk collapse. That's one of the nice things about the silicone, it bends easily... also easy to slide onto old break-prone solenoids, whereas hard rubber will require soap, methinks. Or do I speak from my nethers?

High Temp Silicone

This is what I am thinking.

our silicone hose is:

3.5MM x .105"
4.0MM x .067"
6.0MM x .105"
8.0MM x .115"
10.MM x .135"

If I made the hoses out of 100% Viton and used the the same wall thickness on everything except the 4MM which, I would bump up to .105" to resist collapse, I think I would be ok. Since Viton is a much stronger material, I even think those walls are over kill.

I am the hose industry!

The 100% Viton will act thesame as the McMaster Carr stuff however the ID and wall are much thinner than what I was thinking about. Secondly since we will use 100% I can get to 550F when they max out around 400F.

I used to work for another company we made some of McMasters tubing and silicone. In fact I have a request in here right now from on some flat sheet products going to them.

On the installation side, silicone has a low coeffiecent friction, whereas Viton is higher. That said installation may be more time consuming but you would never have a splitting issue.

BTW Viton is a nightmare to color other than brown or black. So black would be the only color I would offer.

DaveW

Thanks, High Temp.

If you make this Viton in the 0.105" wall in 4-mm, and the other sizes needed for the hose job on the FD, I'll buy whatever quantities are needed to do it!

I figure if I'm going to spend at least one day to do this, I sure as heck am going to do it right.

High Temp Silicone

double post..sorry

reza

I am using viton currently.
And since I put it on 2 years ago, I have 3 occasion where it splits. This always happened where it met either plastic one way valve, or the 4 metal nipple on the LIM, specially the one with bumps on it.

They are not as strong as you would think.

I got them from McMaster for your reference.

Reza

dgeesaman

iTrader: (7)

Sounds great to me. I bought a few feet of the McM viton and when I received it I was surprised by how soft and thin it was, not even close to .105". It's been in my parts bin ever since. I want to check if I bought the higher or lower durometer that they stock.

Viton may be stronger, but it's kinking and collapsing I'm worried about, not tear or tensile strength (which the qutoed 'strength' of viton is probably based on)

Does the temp rating affect how quickly it hardens in the heat? What temp rating does the Si and stock rubber have? Just questioning whether losing some temp rating might be worth the $$.

Dave

High Temp Silicone

Ok I had a thought when I saw that reza said his lines split also. Were these the thin lines that mcmaster sells? I think they offer a .039" wall?

Are all of these splits occuring at a plastic joint/contact? Beleive it or not you can end up with a problem when certain types of plastics and rubber are connected. For example EPDM will craze ABS plastic to the point it will splinter and break.

I can promise you that a .105" wall Viton line will NOT collapse! That is a 76% wall to ID ratio! IF you bought the McMaster 1MM wall you got a 28% wall/ID ratio.

I will work on pricing today. Just like anything else the more I can sell the cheaper they become. The minimum I am going to have to run is around 1500ft of each of the smaller sizes and close to 1000ft of the larger sizes, so there is a considerable investment on my part by doing this.

The lower the upper service limit will affect the longevity. For example if the max temp is 400F and the tube is exposed to 550F for 1 hour, the service life is decreased by a certain amount of time. The only way for me to prove this is by doing a ASTM test for accelerated heat aging. What typically happens is the following:

more heat longer exposure =
decrease tensile
decrease ultimate elongation
increased durometer
decrease in tear

Thats the reason why I would use a 550 rated Viton. At the start of this thread I said that silicone outperforms viton in temperature. That statement was made for commercial grades, not mil-spec 83248C. This viton is rated to 550F which exceeds the max limit on our silicone products.

DaveW

Yup. The McM-Carr Viton I saw was 1-mm (0.039") wall. That's why I didn't buy it.

High Temp Silicone

temp ratings:

83248C Viton 550F

Our Platinum silicone 450-500 constant, 550 intermittently (over 550 will affect longevity)

Stock lines if Buna-N (Nitrile, or NBR) 250-275 max

if Neoprene 250F

I cant imagine them making these thingsout of EPDM because it has no oil resistance.

reza

Yes... all of the splits are at the joint or contacts with the stock parts e.g. one way valve, vacuum/pressure tank, and the metal nipple on LIM.
They do not split in the middle at all. but once the split starts, it would just grow. So to comment on split resistance after it started is none.

I don't know the thickness, but I remember about 70A and 75A durometer, I think I tried the 60A, and on tight bend it would kink.

I don't think Viton will collapse....

High Temp Silicone

Ok this may not fly for a couple of reason. #1 unless I get enough people to purchase 40 kits it is a loser for me. I would have to make an investment of $10,000 in Viton to keep the prices at an acceptable rate.

The kit would consist of:
40' 3.5MM x .105" wall
15' 4.0MM x .105" wall
16' 6.0MM x .105" wall
4' 8.0MM x .115" wal

The cost per foot based on these heavy wall thickness's would be as follows:
HTS
40' 3.5MM @ $4.33/ft
15' 4.0MM @ $4.65/ft
16' 6.0MM @ $6.00/ft
4' 8.0MM @ $8.50/ft

MMC
3.5MM x .039" wall dont offer it
55' 4.0MM x .039" @ $2.69/ft = $147.95
16' 6.0MM x .039" @ $3.74/ft = $59.84
4' 8.0MM x .039" @ $6.03/ft = $24.12

Dont forget my wall is 2.5 to 3.0 times thicker than what mcmaster.

The total price based on the footage above it $372.75. IF we can get 40+ people I will do them for $242.89. (-35%) If the price is still too expensive the only thing I can do is reduce the wall thickness.

However, if you look at the numbers above for McMaster, even if you bought 55ft of the 4MM, 16ft of the 6MM, and 4ft of their 8MM you will spend $231.91. That said you will only spend $10 and change more for hoses that are 2.5 -3 times as thick. I will have to estimate all the weights involved for shipping puposes because viton is much heavier than silicone due to the specific gravity.

What do you think? good or go back to the drawing board and cut the wall thickness down? Personally I would rather put out a bulletproof system than a budget system. Thats the reason we use 4 ply Aramid in our turbo hoses when others are using 2 or 3.

rynberg

For those of you buying McMaster-Carr viton tubing -- buy the english unit tubing. The metric only has 1/16" wall thickness, the english unit tubing is available in 1/8" wall thickness.

High Temp Silicone

Based on the decimal units and products:

55ft .125" ID x .125" wall @ $9.61/ft =$528.55
16ft .250" ID x .125" wall @ $12.20/ft = $195.20
4ft .312" ID x .125" wall @ $14.79/ft = $59.16

Total McMaster kit $782.91

Maybe I should raise my prices!

High Temp Silicone

Metric sizes are only offered in 1MM = .039"

rynberg

My mistake, thanks for correcting me.

And yes, the cost of the viton is worth replacing the rubber tubing twice.....