Infamous Vacuum Hose Job
 

A brief history of a vacuum hose replacement on our '94 FD w/84,400 miles - stock except for Bonez DP.

Sunday, 5/1 - Removed input air ducting, air box, intercooler piping, air pump, alternator, and throttle body - 5 hours

Monday, 5/2 - Removed Upper Intake Manifold, coil assembly, solenoid rack, and about a zillion electrical connectors and hoses. - Note: despite reading several accounts of how to remove the solenoid rack without disturbing fuel hoses, I had to disconnect the two behind the rack; they were covering the three screws. Even after that, only the screw holding one of the fuel hoses in place could be removed. The other two were threadlocked impossibly tightly. So, I removed the two bolts and one screw holding the rear bracket for the rack to the engine and fought it out against the two fuel hoses/tank vent hose combination, which are held on by their own bracket over the rack bracket. Cammed out one of the front four screws holding the rack in; got it out with smallest Vise-Grip. - 8 hours

Tuesday, 5/3 - Replaced hoses on solenoid rack plus some other hoses in car. Found that my 1/8" ID Viton hose (from McMaster-Carr) would not fit over the 4 mm nipples on the solenoids. (1/8 " = 3.175 mm) Using silicone grease ("Sil-Glyde") and a tapered scribe, lubed each hose end. Then it worked, but fit is very tight. Broke one solenoid nipple (EGR, $66) trying to take off old hose; after that, was super careful and slit all hoses on plastic nipples. Tested greased hose on nipples with MityVac; at 17.5 psi pressure (max I could get by hand) the hose doesn't budge, even without tiewraps. Mazda didn't use them, so I am not either. Will report on that later in case of hoses blowing off. The pressure tank hoses are accessible and obvious with the car completed; will watch those over time. Should be OK at 10 psi. Eventually the engine heat will probably fry the grease anyway. Discovered I DO have to remove the Air Control Valve assembly. Not looking forward to that. Will pick up new solenoid valve and finish all hoses on the solenoid rack tomorrow. - Note: 2 of the "4mm" hoses had to fit over larger hard pipes on one end only. Had to "customize" those by reaming out their ID. - 8 hours

---- Bill

dont pull, twist

good luck

rotoboy,

Broke when twisted gently... these things are FRAGILE! (Maybe already damaged?)

---- Bill

yeh and from the intense heat from engine and age

i also sprayed wd40 on them and le them soak in a lil then they just came right off with a tug

If I were you, I would test the solenoids for operation too. I ended up replacing all of mine (dent in the wallet) due to some not testing well and some werer broken

cut hoses with exacto..then split open...

Great advice. Cut, split, then twist. Works every time.

My hoses were so hard an x-acto wouldn't cut them. I used a short length of hacksaw blade and cut a notch in the hose lengthwise along the nipple. I then inserted a screwdriver into that notch and twisted. The hoses would break into many pieces and not damage the nipples or solenoids. I did break one before I started doing it that way though...

You can also heat the hose ends with a lighter. I use one of those candle lighter jobs - hope my wife doesn't notice it's missing :). The heat will make the rubber more pliable, then you can slit the hose.

Dale

I just heated up the old hoses with a direct flame (lighter) until they started to smoke. Then I used a flat screw driver and "popped" the hose directly away from the solenoid to get it loose, then I just pulled it off. This worked flawlessly. I tried to use the cutting method, but some of my hoses were way too hard to penetrate even with a brand new exacto knife. I worried about the amount of pressure it would take to slit the hose might cause me to break the nipple off anyways.

Yea, one more thing. Your first step took 5 hrs? Dang. But being careful doesnt hurt anything. Hope all your new hoses work out great.

Thursday, 5/4 - Replaced the broken solenoid valve and finished the solenoid rack internal hoses. Removed the Air Control Valve and replaced the "hidden" four hoses. Replaced the four turbo and turbo actuator hoses, which required going under the car. Mazda did me dirt by putting a 6 mm hose on the "8 or 9 mm" turbo control actuator pipe. Their hose would stretch to fit, but my Viton would not, until I cut a taper into the ID at the hose end. I'm done replacing hoses now; time to start putting things back together. All my new hoses are color-coded with paint where needed, so hopefully I won't get anything crossed. First item to reinstall tomorrow is the Air Control valve. I put a little gasket maker around the outer edge of that check valve, so hopefully it won't de-center when the ACV goes on the manifold. Biggest worry now is deciding how to put the solenoid rack back in. I'm inclined to connect that rear bracket with two of the screws in the rear of the rack before sliding the rack in... the screws are just impossible to get at with those fuel hoses in the way. But that means I might have to disconnect two more fuel hoses... don't really want to do that.

I have towels on the fenders; unfortunately when I was working on the topside of those turbo control vacuum thingies, I leaned on the inside rear corner of the right headlight cover and cracked the plastic bracket underneath. Tried an epoxy repair tonight... hopefully it will be glued tomorrow. My wife will not like that... it's her car.

If I had not had those Craftsman xtra-long nose pliers, I could not have replaced those hoses under the solenoid rack, or the ones on the turbo control actuator. That was an invaluable tip from Max Cooper.

---- Bill

In case you hadn't read this one, I wrote some hose job notes too:

www.davidgeesaman.com

I strongly recommend printing out the vac hose diagram, tacking it on the wall, and double-checking everything. I also found that the viton hose did not stretch well to fit over the TCA nipple. If the stock hose isn't brittle feel free to re-use it as those hoses don't fail often.

Dave

Duh, my last post should have read "Wednesday, May 4.")

Thursday, May 5 - Checked solenoid coils, all were 37.7 ohms. Did not check operation because the car runs well. Installed solenoid rack. My fears were unfounded... the additional fuel lines did not have to be disconnected. Installed coil assembly. Installed UIM. Getting those hoses under the UIM was not fun, but did eventually work. BTW, I had a 3-ring binder with several different versions of the vacuum hose diagram by Rob Robinette, Brian Davies, et al. Another Mazda pain... a check valve clearly a 6 mm size with a 4 mm hose on it. Had to cut a taper into the ID of my 1/8" Viton again (same as turbo control actuator nipple problem on the 6 mm hose). I think everything is hooked up OK so far... I did notice when inserting the restrictors in the turbo control lines that they have a slight "leakage" around their circumferences. Don't know if that was true of the OEM or not. Probably not a problem (I hope). Not working on car tomorrow; it's our wedding anniversary. Saturday will be throttle body installation day, plus whatever else I can do.

---- Bill

i'd love to attempt the vacuum job but am too nooob to try......how much would a shop charge for a job like that.......1000 bux????

There's no reason to do it unless you are experiencing problems with boost and or the fuel system IMO. Especially if you have a very high mileage engine -- better to just do it during the rebuild when the labor and difficulty is much less.

I believe most good RX-7 shops would probably charge around $4-500 for labor for this job. Of course, that doesn't include the cost of hose, or any broken solenoids, check valves, fuel system parts (FPD), etc.

sweet.....thanks rynberg........now i know, and knowing is half the battle ;)

RE: the check valve - I bought an adapter from 3/16" to 1/8" to step up from the 1/8" hose to the check valve.

The pill lines should hold them securely without leakage - a little extra leakage though might reduce your boost level a psi or two. I would be more concerned that the pill would get turned in the line and reduce the effective orifice to zero, and push your boost levels way up.

Dave

dgeesaman,

"I would be more concerned that the pill would get turned in the line and reduce the effective orifice to zero, and push your boost levels way up."

Yes, I was concerned about that, so I oriented the pills correctly and then bent the hoses back & forth several times and looked to see if they had turned. They had not. I would expect that if that happened, it would be when I installed the hoses. After that there is only airflow through them... hopefully that will not turn them. The "leakage" I saw was just the slightest amount of light in a couple of places around the circumference. My hoses are 1/4" inside diameter which is 6.35 mm, as opposed to the nominal 6 mm of the OEM, so that could account for it.

rynberg,

I'm an optimist and do not plan on rebuilding this engine; the car has been pretty well babied for its entire life. I have read reports of rotary engines being torn apart at 100K miles, with the original satin finish still observed on the insides of the rotor housings. This is a type of car that is frequently flogged, so I understand your point of view, which is probably valid for most owners. I am doing this job as preventive maintenance, and because the rotary tech at Irvine Mazda said he would NOT do it using anything but a factory replacement "kit" of OEM hoses. The estimated price was around $800 plus the hose kit. (They were supposed to call me back when they had a quote on the "kit" from Mazda's supplier, but they never did.) BTW, some of my old hoses are no longer rubber; they are hard plastic. Time to do the job! Besides, most of the vacuum controls affect emissions, and I don't want it to fail as a gross polluter AGAIN, and have to spend $1250 on another OEM catalytic converter. (The aftermarket Bonez didn't work.)

---- Bill

IIRC, Malloy Mazda (Roy Crowe, 888-533-3400) offers the kit (preformed hoses & check valves, etc.) for ~$160 including free shipping. These will last for another 10 years. I did mine using HTS Viton, but that may have been overkill.

Sunday, May 8 - Finished yesterday after a day off Friday. The car runs, (yay), though wifey only took it around the neighborhood. I asked her how the turbos work, but she didn't try that yet. Had no parts left over. A good sign, yes?

The Viton hoses I used in the 1/8" ID size are REALLY tight. However once over the bulged ends (of those pipes which have bulges), they slid on without too much drama. I had no problems with clearances even though the OD of the hose is about 3/8", notably bigger than the OEM hoses. There is one upward-looping hose on the solenoid rack that is pushed down slightly to the side by the bottom of the pressure chamber, but it is not deformed.

The 1/4" ID size, even though 6.35 mm instead of the 6 mm OEM, is still pretty tight in all places except one, and I used double tie-wraps on both ends of that one.

Could not have done this without the several downloads from previous forum members and independent websites like http://rx7.voodoobox.net/howto/vachose/vacjob.html and the excellent modified illustrations from the factory manual, such as http://www.zeroglabs.com/rx7/images/...oses.color.jpg

Hope I never have to do this again!

---- Bill

Then a couple of thin zip ties should be enough - one immediately before and the other after each pill to snug the hose and keep it sealed. As long as the ID of hose isn't reduced much it will be extra safe.

Dave

Dave,

Thanks for the idea! I'll do that right away.

---- Bill

Dayam the bonez didnt work!!!!! I just put that on my car!!!! man I bought that cat so i could pass heheh.....

dgeesaman, You are fantastic, i have a lot of work to do on my RX7 and it will be much easyes thanks to You

does arrow on air bypass valva go toward airbox?