i just don't like the idea of silicone vac lines. they're not oil and gas resistant and are prone to cracking tearing from abrasion. the stock lines have lasted 13 years and 125k miles on this car, so tell me, what is so bad about rubber?

i was going to use viton, but it's very expensive. i decided rubber will do just fine for most areas and with the money i save i can get a new pulsation dampener and have my injectors cleaned (not that i wouldn't have otherwise).

also, what are the hoses coming from the wastegate actuators made of? mine are still in excellent condition and i plan on reusing them.

 

Use good rubber lines and you should be fine.

 

Nothing wrong with rubber lines. Just don't buy low quality rubber.

 

HoseTechniques.com

 

I think you can get the whole stock rubber line set (these are preformed lines) for around $100 from Mazdatrix. You might want to call them and see if they still have the kit for this price.

Silicone doesn't have much resistance to fuel/oil, but neoprene rubber isn't much better. Neoprene hardens with heat, silicone holds it durometer or softens. IMO the silicone is marginally better for this reason, but in either case they shouldn't be exposed to these elements anyway.

Dave

 

Nothing beats VITON, for certain. But for most people it is not cost justified.
I like having the best so I used VITON. Personal preference, but as others have stated, good quality rubber works very well also.

 

Has anyone ever actually had a silicone vacuum line fail in application on an RX-7 due to "normal" exposure to the elements in it's operating environment?

Joe

 

i was just going to buy one of those rolls of "thermoid" vac lines off of ebay...

i read a thread where someone was having problems with their silicone lines splitting. it was probably **** silicone. silicone in general has poor abrasion and tear resistance though. but if i'm going to upgrade from rubber it's going to be to viton.

where did you find viton hoses anyways? mcmaster carr only sells them with 1mm wall thickness, which basically worthless for any use. this is for 4mm and 6mm.

 

wtf... ricer bs. i'm not buying from a company that has a "fast & furious twin color hose set".

 

The only reason silicone will split is if the cut is not clean or the hose is knicked on something. If care is taken when installing, there should not be any problems. I'm not discounting rubber or viton; but all things considered, silicone is the best all-around solution, in my opinion.

Joe

 

You may find this interesting

http://www.geocities.com/MotorCity/Garage/8255/hosetest.pdf#search='silicone%20hose%20test'

 

http://www.bakerprecision.com/hosetech.htm

 

hose techniques makes quality stuff. I use their couplers and their vaccum hoses. They have held up great for me. The hose techniques set is what rx7store sells. Don't knock just yet. They do need to appeal to a broad market to maximize profits.

 

http://www.rx7.voodoobox.net/howto/vachose/vacjob.html Read what this guy has to say about what vac line to buy.

 

Hose Techniques sells quality silicone hose regardless of their affinity to any ricer icon.
Nothing wrong with rubber, but I suspect the silicone hose has a higher melting point.
After my recent underhood fire, I was amazed at how well the silicone hoses held up.
The OMP lines and wiring harness were toast, but there wasn't a single vac hose that needed to be replaced. I replaced a few of them for appearances sake only.

 

That is an interesting article, but it is a little out of the realm of reason when applied to the operating environment of the hoses on an RX-7. While there could be some traces of oil in the vacuum hoses, the majority of oil is found in the intake tract. The silicone couplers are more likely to fail than the vacuum hoses. If there were enough oil in the hoses to do damage, other components would fail first. Namely, the sequential operation of the turbos'. The actuators operate off of vacuum, not hydraulics, which would be the result if large amounts of oil were present in the vacuum lines.

Another reference point would be using sulfuric acid to unclog a drain. If the acid is left to sit in the pipes, it will eventually corode the pipe until a leak develops. However, if passed through the pipe per the instructions, it does it's job and does no harm to the integrity of the pipe.

The point? Hot oil misting through the vacuum hoses will not compromise the integrity of the silicone. Silicone that is submerged in hot oil will loose it's structural integrity.

Joe

 

Then don't buy it, don't use silicone. I have silicone hoses in my car...no problems at all. Yes, I bought it from the "fast & furious" company. I wouldn't put down a product unless you have first hand experience. You have two other choices, rubber or viton...viton is too expensive for you...then you have your answer.

 

The alternative is to set up a more realistic set of conditions for the test and wait 5-10 years. Accelerated wear tests like this are very common and also useful.

As for the fuel and oil source - the vacuum system gets all of its pressure and vacuum from the intake. So at least the pressurized lines would get a shot of oil/fuel on a consistent basis. My FD had silicone lines in the rats nest that had faded and softened quite a bit since they were installed. I installed viton, but only because I figured I may never get another chance to purchase that product. Good quality silicone is a very cost effective and high performing product. And it's not ricer if you buy it in black. An alternative source to the F&F place is hightempsilicone.com.

Dave

 

as others have already stated:

http://hightempsilicone.com/category...kits.mazdarx7/

this is what I got. They actually give you more than you need, but it is cheaper by about $100 to buy the kit rather than to order X number of feet of each size.

 

hightempsilicone.com looks solid... their curing process is supposed to be better. they are also developing a viton kit... it's around $300 though.

edit: that's wierd, i checked there a while back and it said it was in development or something. maybe i'm just nuts.

like i said, i won't. i had already stated that i don't think it's the proper material for this purpose. additionally, the only hard evedince i've seen (though the testing conditions were a little extreme) showed me that silicone is not even as good as neoprene rubber. for the most part, i think alot of the silicone vac lines out there are low quality material and just for the bling factor. as far as hose techniques, i don't think any self respecting vendor should bite off of that crap movie, but that's just me.

anyhow, seeing as how viton will be harder to find and many times the cost of neoprene (8X-10X) i'm just going to go rubber and focus on keeping stray oil, fuel, and heat under control in the first place.

besides, i still haven't found where you can buy viton with the right wall thickness in the 1st place.

 

alexdimen, the Hose Techniques VITON is the right stuff as far as wall thickness goes.
But yeah, rubber has lasted most folks for 10 - 13 years so no problem using it.

 

There's a lot of "bench racing" out there on the topic of vacuum lines. Here's what I know from REAL WORLD experience over MANY years.

The stock vacuum lines work GREAT, believe it or not, UNTIL you try and disconnect them. They are rubber, and it vulcanizes with the heat over time, turning it into hard plastic.

For vacuum lines that you NEVER have to remove, like most of the ones down on the rat's nest, just leave the stock hoses be. For hoses that have to be removed and reconnected frequently, like lines going to the upper intake manifold, replace with silicone. Good to go.

I have installed literally HUNDREDS of feet of Hose Techniques vacuum hose, and I have YET to see a failure. I have even used them on PCV lines that see LOTS of oil, and haven't had a failure - they do degrade, but they don't fail.

I have seen and worked with cheap silicone vacuum line, and that's where the bad rap comes from - it's thin wall, kinks easily, doesn't fit right, and will easily split and degrade.

Here's my winning recipe -

- Hose Techniques (or High Temp Silicone.com) 3.5mm and 6mm lines for any hoses that are removed for service. This includes blow-off valve vacuum lines, lines to UIM from rat's nest, and DEFINITELY the line to the MAP sensor. It will fit right, last forever, and be good for many cycles of removal and installation. Get about 20 feet of 3.5mm and 5-10 of the 6mm, and you'll have plenty for now and some extra for later. BTW, the 3.5mm fits GREAT - you really have to tug to remove them, and I've never bothered with zip ties or wire ties - total overkill. Guys who have done that in the past have used improper sized hoses that don't fit tight. Use the right size and you will NEVER have a problem.

- If you do any of the PCV lines, use 6mm Viton. I'd get 6ft or so of it for that application - that's a perfect place to use it. IMHO, Viton lines everywhere else is just extra money, and some of the Viton out there isn't as thick-walled or good-fitting as I'd like.

- Of course, Viton check valves .

Do that, and I guarantee you'll have a great, trouble-free vacuum line setup that will last for years to come.

BTW, I don't fault Hose Techniques for doing the F&F thing. They're a company, they want to make money. You can sell to the 10% of hardcore enthusiasts who want a quality part to work hard, or sell to the 90% dumb ricer market that want to put colored silicone everywhere because it looks cool. I don't fault them for it.

And, yes, I use BLACK silicone vacuum hose. Colors are neat, but they just get dirty looking over time.

Dale

 

I've used hosetechniques silicone for the last 5 years and ~60k miles and never had to replace a line due to failure.

I also have a set of hightempsilicone intercooler couplers that are really nice as well.

Under normal conditions, I think it's safe to say that high quality silicone lines will out last your engine!

 

When it comes to a rotary, that is probably the best marketing statement for silicone that I have ever read.

Joe

 

Dale's right, rubber is fine IF you never touch it, but my question to the original poster is, why you WOULDN'T just use silicon? Then there's definately no problem.

A LOT of people had running problems with the original rubber. That's where the ubiquitous "silicon tie wrap job" came from in the first place. Mines been done since '98 or so. I was the 2nd thing I did (after a catback).

If I had it to do over right now, i'd go with 100% viton (nobody's heard of it in 98). Of all the things you'll pour money into with these cars, HOSE PRICE is the thing you're going to get hung up on after you've taken the manifold off and sweated over the rats nest for a day or paid $500 in labor to have it done? Sorry, but F-that. That's a job you want to do ONCE. Pay the extra couple bucks for the good stuff while you're in there.