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DaleClark's guide to vacuum lines and your FD

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Old 05-18-10, 08:34 PM
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DaleClark's guide to vacuum lines and your FD

OK guys -

I've started to realize I'm posting up this information over and over again, so it's time for a nice, neat thread with the information all summarized and put together.

This is a simple guide to vacuum lines on your FD. There's a lot of misinformation, misunderstanding, and mistakes out there with regards to the mess of vacuum lines under the hood of the FD. This will hopefully shed some light on the topic.

Note, I've been hardcore working on RX-7's since '96, got my first FD in '04, and have worked on a ton of FD's for friends and customers since then. I'm not guessing or going off what I've heard, this is hands-on experience over MANY years and seeing the results over time.

First off, tools. One of the handiest things I've bought to deal with the vacuum hose is a LONG set of needle nose pliers. These make the job SO much easier.



Those pliers are from good ol' Harbor Freight, and the snips are probably from them as well. The snips you can get most anywhere, they're great for cutting vacuum line. The pair of long needle nose are currently $6.99 from Harbor Freight -

http://www.harborfreight.com/2-piece...ers-33203.html

OK, next is the big part, getting the vacuum hose itself. My recommendation -

BUY GOOD SILICONE HOSE.


Notice I say *GOOD*. The problem is people over the years have used cheap and crappy silicone hose and it's given silicone a bad name. I know, I've re-done a few vacuum hose jobs that were done with crap.

The good part is it's easy to buy good silicone vacuum hose. http://www.hosetechniques.com is where I've been buying my vacuum hose since day 1. The stuff they have now is the same they had when I placed my first order 10+ years ago. It's thick-walled, oil resistant, fits tight, and grips like a bear. It's also reasonably priced.

Now, many people are saying "You gotta use viton, it's the best, oil doesn't destroy viton, buy the good stuff for your FD!" First off, I'll be the first to raise my hand when asked "do you spend the extra money on your car for the right parts?" But, I don't spend money where it's not needed. This is definitely one of those areas.

A lot of this comes from an old test that someone did comparing Viton and Silicone vacuum hose. After soaking the hoses in oil and applying heat, the Viton held up great, the silicone had degraded substantially. First, it's not a real-world test. Second, CHEAP OFF-BRAND silicone hose WILL degrade big time with oil exposure, I've seen it. Hose Techniques hose WILL NOT. I actually used Hose Techniques hose for the lines to my oil catch can for about 2 years - it was SLIGHTLY swollen after that time, but that was about it.

Viton is also a very stiff hose, where silicone is really flexible. This makes it much easier to install the silicone. This can also lead to the plastic nipples on the solenoids snapping off when installing the Viton hose as you really have to push and shove to get the Viton to deform enough to fit onto the nipple.

Finally, cost. Viton hose costs 2-3 times that of Hose Techniques. You're paying more but not getting more.

Now, I DO recommend using Viton in places of oil saturation, like the aforementioned lines to an oil catch can. But, you only need a few feet there instead of the whole shebang.

OK, let's compare the good silicone hose with the junk. I saved a hose off a previous vacuum job I did to compare.



The HT hose is on the left, it's a leftover red hose from my old FC when I thought red hose would look cool . Notice how much more thick wall it is. Also, notice the size of the inside diameter of the hose - it's smaller. This is the 3.5mm hose, this gives a perfect, tight fit. Most of the cheap stuff is larger and makes for a loose fit. This is why, back in the day, people would zip tie and glue all the hoses. This is completely unnecessary with the right size hose. Also, the HT hose grips VERY tightly and really takes some work after a few heat cycles to remove the hose. This is what we want - it won't be popping off.

Now, hose kinking is another problem. Showing the two hoses again -



Notice the HT hose is not kinked, the other is, even with a relatively mild bend. The HT hose, even with a VERY tight bend, will not kink. This is due to the nice, thick walls of the hose.

Hose color is another topic. As I stated, I had red hose on my FC back in the day. Over time, this nice, pretty color will get dirty and nasty looking and it's a bitch to clean. Just get black - HT's black is a nice, shiny black, looks good on any car, and always looks clean and neat.

Cutting the hose - again, this is another area where cheap silicone has problems. The cheap stuff will split if you have a ragged cut, HT won't. It's still a good idea to make a nice, clean cut - I always use a pair of snips to snip the hose to length. I've never had HT hose split on the end or cause any problems.

How much hose to get? This is a tough one. I prefer to get too much than not enough. I'm always finding a use for the hose, or you might need extra to hook up a boost gauge or boost controller. I'd say minimum 20 feet of the 3.5mm, and 5-10 feet of the 6mm hose. You'll want more 6mm if you have a boost controller.

Check valves are the next topic. Real simple here - the stock check valves are crap; they break, stick open, and they're horribly expensive. I sell Viton check valves, PM me if you need some. If you still have the stock check valves, they need to go, pronto.

Speaking of, this is where you can see the flexibility and fit of the HT hose. The 3.5mm fits TIGHT on the Viton check valves, they aren't going anywhere -



Now, there is a filter in the line to the MAP sensor. THIS IS NOT A CHECK VALVE. I've seen cars with a check valve here. The OEM filter seems to do just fine, leave it be. Here's what I'm talking about -



OK, so you have your tools, your hose, your check valves, and a head full of know-how. What next?

You're gonna need a GOOD copy of the vacuum diagram. Head here -

http://www.turborx7.com/images/Techn...e_diagram2.jpg

and save a copy of that file, that's the colored vacuum diagram. Copy it to a flash drive and take it to your local Kinko's. Have them print it in color on 11x17 paper and laminate it. Voila, you now have a VERY nice grease-resistant copy of the vacuum diagram and it will cost you about $6.

So, time to tear into it. Here's my rules of thumb -

- If the vacuum hose is baked on there, leave it be. It isn't going anywhere, it's not going to leak, and there's no point in changing it.

- All the vacuum lines going to/from the intake manifold MUST be changed to silicone. They get a lot of abuse from pulling the upper intake manifold and they likely aren't fitting and sealing properly.

- All vacuum lines with check valves need to be replaced.

- Vacuum lines to the stock blow-off valve and CBV should be replaced. The nipple on the BOV's is a little largish, but the silicone will stretch to fit.

- Vacuum line to the MAP sensor MUST be replaced. Many times the stock line isn't fitting well anymore and wants to pop off. Replace it with silicone, and it will stay put.

- Yes, the vacuum lines look real confusing and crazy at first. Just take your time and go one by one, using your diagram. It's not bad when you get into it.

- Another trick to installing the vacuum lines - before you install it, lick the ends of the lines. The spit will help lubricate the hose so it will slide on easily. Sounds weird, but it works great and really makes the installation simpler. Also, the spit will soon dry up and not stick around to cause any problems, like some sort of spray like WD-40 would. If you're weird about it, have a little cup of water and Dawn mixed up and dip the ends in that.

- Vacuum caps. You'll need them at some point. The caps from the parts store SUCK, they will split in a few months and leak on you. Order EPDM vacuum caps from McMaster-Carr, they're inexpensive and will hold up for a long time. Head here to order -

http://www.mcmaster.com/#epdm-rubber-caps/=75ecvs

You want the "chemical resistant" ones, the "high temperature" ones aren't necessary.

There ya go. If you tackle the job right you'll never have any problems now or down the road. My car has 114,000 miles on it with a perfectly functioning sequential system - do everything right and yours will too.

Dale

Last edited by dgeesaman; 05-19-10 at 03:58 PM.
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Old 05-18-10, 08:55 PM
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good call on wetting the lines before installation
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Old 05-18-10, 08:59 PM
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Awesome writeup Dale, the only thing I would add is testing your solenoids while you're under there as well as a note to make sure folks don't loost their boost pills when replacing lines.

FWIW if you order the Hose Techniques kit for the FD you'll get plenty of the right sizes of hose, plus tie wraps (not really necessary at stock boost) and a hose cutter which works great. Can't say enough good stuff about Hose Techniques, my experiences with the product and their staff has been really nice.

Your check valves are also an incredibly good product.
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Old 05-18-10, 09:29 PM
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+1 on HT. I've used their couplers for years and have been very pleased with the products they put out.
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Old 05-18-10, 09:35 PM
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I would also agree with the Hose Techniques suggestion, and thank you for spelling this out for the people who are inexperienced! There has been a lot of confusion lately.
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Old 05-18-10, 10:13 PM
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I'll second getting Dale's check valves and HT silicone. Been running both now for a few years with no issues. The valves are one of the best bangs for the buck you'll find. And I think it was his prior posts that made me decide on HT silicone over Viton. I have no regrets and kept about $200 extra to spend on other stuff.
Unfortunately HoseTechniques no longer offers a "kit" for the FD...which included all the needed lengths and sizes for a full sequential system WITH emmissions. FWIW as a reference, these are the lengths they offered back then in the kit. But if you have deleted emissions, you'll have lots left over.....especially of the 3.5 size.
40' of 3.5 mm
15' of 4.0 mm
16' of 6.0 mm
4' of 8.0 mm

I will disagree on problems keeping the colored hose looking nice. My red ones still look fine going on three years. If I do get some dirt or grease on one (usually from grabbing them with dirty hands) I just wipe it down with a little window cleaner on a rag.
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Old 05-18-10, 10:37 PM
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I just checked, you can still get the FD kits at (this one is red)

http://www.hosetechniques.com/silico...lor-red-p-1925

+1 on Windex though, thats what I use to keep my red ones red. It is a bit harder to keep clean than black would be though hehe (but I still prefer the red!)
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Old 05-19-10, 12:43 AM
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Originally Posted by DaleClark View Post
Viton is also a very stiff hose, where silicone is really flexible. This makes it much easier to install the silicone. This can also lead to the plastic nipples on the solenoids snapping off when installing the Viton hose as you really have to push and shove to get the Viton to deform enough to fit onto the nipple.
Good information - but I beg to differ about the workability of Viton. I just did my rat's nest (with five-year-old Viton) and it was a joy to work with. Yes it needs very slightly more pressure to install than silicone but you know that it is not going anywhere when it is on.

I also found that rolling the end of the hose vigorously between my finger and thumb for 10 seconds or so to warm it up made it more flexible when installing.

The cost difference meant nothing to me because it was dwarfed by the amount of time involved. (And is probably less than 0.5% of the amount of money I have spent on my car. )

Again, it may come down to the type of Viton hose. I used the HighTempSilicone stuff, which was absolutely top notch. Too bad that they are out of business. (If anyone has any old HTS stuff to sell, I'll buy it, BTW.)

I also found these puppies to be absolutely killer in making clean cuts on hose ends:

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Old 05-19-10, 01:03 AM
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Is there a quality silicone hose that has the satin finish like Viton?

I like the OEM look over the shiney stuff
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Old 05-19-10, 07:53 AM
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Great write-up Dale! I think this should be added to the FAQ and/or stickied
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Old 05-19-10, 08:04 AM
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Originally Posted by twinsinside View Post
I just checked, you can still get the FD kits at (this one is red)

http://www.hosetechniques.com/silico...lor-red-p-1925

+1 on Windex though, thats what I use to keep my red ones red. It is a bit harder to keep clean than black would be though hehe (but I still prefer the red!)
I stand corrected.
I checked their site a few of months back for a friend replacing his hoses and I couldn't find it. At any rate, thanks.
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Old 05-19-10, 08:21 AM
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Originally Posted by Prometheus View Post
Is there a quality silicone hose that has the satin finish like Viton?

I like the OEM look over the shiney stuff
Not that I know of. I think it might just be the nature of the material itself that it's shiny. If you get black it really isn't that showy.

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Old 05-19-10, 09:05 AM
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Nice writeup! Any rough count on sizes and quantity of vacuum caps required?

Also, looks like the inline pictures are broke.
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Old 05-19-10, 10:38 AM
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Not sure why the pictures are broken, they were uploaded to the forum and it's not showing it any more.

Anyhow, can't really say on number of vacuum caps needed. A bone stock car you'd need none, but if you start removing things like AWS, EGR, etc. you'll want vacuum caps.

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Old 05-19-10, 10:50 AM
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Ya, I'm far from stock... Most of the caps I have are the generic rubber ones and are starting to show age, guess its time to bust out the caliper and figure out sizes. I'll report back with my findings on what components have what ID.

And +2 to this should be stickied
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Old 05-19-10, 12:14 PM
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Great job Dale, this will help a lot of people...and those cheap auto store caps really do crack VERY fast, you'd be lucky to even get a couple months out of them.
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Old 05-19-10, 12:45 PM
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Originally Posted by DaleClark View Post
Not sure why the pictures are broken, they were uploaded to the forum and it's not showing it any more.


Dale
I don't think you can hot link attachments

This thread is now linked to from the FAQ thread.

Last edited by gracer7-rx7; 05-19-10 at 12:48 PM.
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Old 05-19-10, 05:34 PM
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Images are now fixed - thanks David!

Another word on vacuum lines:

- Vacuum T's. NEVER EVER EVER use plastic vacuum T's for ANYTHING. I have PERSONALLY known 2 people who have BLOWN THEIR ENGINES due to plastic T's cracking and failing from heat. Only use brass. For the smaller vacuum lines, you can find brass T's at pet shops in the aquarium section - they're very high quality, barbed, and fit perfectly. For the larger T's for the 6mm hose, I found some at Pep Boys in the past, McMaster-Carr is another good place. The larger ones are needed many times for hooking up a boost controller - this is one area where a T can fail and cause bigtime overboost.

- Never T into the MAP sensor line. The input to the MAP sensor is absolutely critical to the engine, and you need to prevent a possible point of failure. There's just no good reason to T in, especially since there's the nipple for the boost gauge hookup. If you do need to T in for some reason, I prefer to T into the boost gauge hose.

- On the lines for the wastegate and boost control with an aftermarket boost controller I do prefer to use a clamp or zip tie to secure the lines. Again, if these pop off or come loose you can overboost and cause major damage. On Ebay there's a guy selling nice 8mm spring type hose clamps that should work, I've been meaning to get a bag to try out. Zip ties work but they sometimes fail from heat over time, worm drive clamps can eat into the hose and cut it over time. The silicone does grip VERY tightly and it's a slim possibility that it can pop off but I like to make extra sure.

Dale
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Old 09-29-10, 01:44 PM
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Dale, are those check valves you're selling sourced from Ark-Plas? They look similar to the ones I got a while back. BTW, I'm running the stainless steel SMC 110's (all 4, I'm not using the Pettit check valves anymore). Haven't had any issues with them to date.
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Old 09-29-10, 02:51 PM
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Great thread Dale
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Old 10-30-10, 06:29 PM
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So what size is the hose that goes to the center of the Turbo Control Actuator? Is it 8mm?

The one on the side of the actuator fits a 6mm hose w/o issue. I've been trying to replace the old hose on my car and 6mm doesn't seem to fit the nipple in the middle of the turbo Control Actuator. There isn't much room in there to get to it with the motor and turbos in the car. What a pita...
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Old 10-30-10, 10:10 PM
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wow, thanks for all the info.
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Old 10-31-10, 01:31 PM
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you the man Dale..... you have helped me alot in the past fixing things myself.. this is why I joined the forum.

Jeff
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Old 12-28-10, 07:44 AM
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About to do the vac line job. Other than the hose, zip ties, check valves, vac line diagram and tools are there any other OEM parts that need to be replaced? I've heard replacing the fuel pulsation damper is a good idea. Any other gaskets or parts I need to get?

Is there any point in removing and testing all the solenoids if the twins are working properly?
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Old 12-28-10, 09:01 AM
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While replacing the FPD can be a good idea, you really have to get deep into the engine to replace it, deeper than doing most of the vacuum lines. If you're in there I would pressure test the fuel system to determine that it's leak free.

I can't really think of any OEM parts that would be necessary. Of course there might be some you'll end up needing when done, like if vacuum nipples snap off on you.

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