How To: Installing a Street Unit rear motor mount on your MSP

Discussion in 'Facts and How To's' started by dmention7, Jun 30, 2007.

  1. dmention7

    dmention7 Hater

    This writeup is for all Mazdaspeed Proteges. I'm also fairly certain that the major steps are accurate for any 3rd gen Protege.

    I'm doing this writeup for two reasons: 1) The rear mount is the only one that cannot be easily swapped without other disassembly, and 2) The writeups on and are pretty barebones, and do not (in my opinion) adequately document the details of the install you need in order to perform the job smoothly.

    As an aside, this install requires you to remove the throttle body, so its an excellent time to clean the EGR (exhaust gas recirculation) valve--a common cause of rough idle.

    Estimated Time: 4-6 hours
    For me, getting the mount out was about 3/4 of the time I spent. Reassembly goes fast.

    List of tools/supplies you'll need:

    -Phillips screwdriver
    -Flathead screwdriver
    -Pliars (preferably vice-grips)
    -8mm socket
    -10mm socket (1/4" drive)
    -17mm socket and deep socket (1/2" drive)
    -1/4" ratchet and/or nut driver
    -1/2" ratchet and breaker bar
    -Your entire stash of 1/2"-drive extensions (probably a 12", 6", and 4") and a U-joint
    -A 3" extension and U-joint for 1/4 drive
    -RTV gasket-maker or a new throttle body gasket
    -Brake cleaner (for cleaning the EGR valve)
    -Liquid wrench, or other spray lubricant
    -A pair of M14 size bolts, or something of a similar diameter


    1. Remove strut bar and battery cover
    2. Remove IC coldpipe
    3. Remove throttle body
    3a.Disconnect throttle cable
    3b.Unbolt and remove TB
    3c.Unhook and plug coolant lines from TB
    3d.Remove EGR valve
    4. Unfasten wiring harness from firewall
    5. Remove long bolt running through mount
    6. Unbolt mount from frame and remove
    7. Clean EGR valve if desired
    8. Reassemble everything in reverse order from disassembly

    And away we go! (note: all these pics were taken during reassembly, so you're looking at the street unit mount, not the stock one)


    1) The first thing I did (and this isn't in any of the other how-to's I've seen) is remove the strut tower bar. It takes about a minute (4 17mm nuts), and it eliminates the need for a 2nd elbow later on when you're up to your neck in the engine bay. Thread the nuts back onto the bolts so they don't get lost, and set the bar aside someplace safe (don't want to scratch it up!)

    Also, remove the engine cover using a 10mm socket on each of the nuts that secure it. Thread the nuts and washers back onto the bolts to keep them from getting lost. Again, it only takes a minute, but it gives you a bit more room to work.

    2) Remove the IC cold pipe--it's the pipe between the IC and the throttle body. If you have the stock pipe, it's secured at both ends by hose clamps--use an 8mm socket on a nut driver, or a flathead screw driver to loosen those up. It takes a bit of work to wiggle the pipes loose. Also, there is a small solenoid or something attached to the top of the pipe--remove that with the 10mm socket, and tuck it out of the way. Be careful not to put much force on the stem that solenoid is attached to, when removing the pipe.


    3) Removing the throttle body takes a few steps. There are three electrical connectors--two on the throttle body itself, and one at the bottom on the EGR valve.

    3 a) The throttle cable also has to come off. I found the easiest way to do this was to prop the throttle plate completely open--use something that won't drop crud all over inside, or fall into the intake manifold! Once you have slack in the throttle cable, you can slide the cable and the peg that anchors it out towards the firewall. It's hard to explain, but play around for a second, and you'll see how it works.

    3 b) You'll also have to remove the two small coolant hoses that run through the TB, but it's easier once the TB is unbolted. Use a 10mm deep socket, or a socket with a short extension, to reach the 2 bolts on the top side of the TB, and the 2 nuts on the bottom side of the TB. It might be stuck to the intake manifold, but give it a good tug to break the gasket.


    3 c) Now that the TB is hanging around, you can reach the coolant hoses a bit more easily. (NOTE: it's best if the engine is cool, so there will be no pressure in the coolant system) They are on the front side of the TB (facing the front of the car), and one is toward the top, the other is toward the bottom. Use a pliars or vice grip to slide both clamps off the hoses. Keeping the TB elevated, remove the top hose while pinching the hose shut. Plug up the end of the hose with one of the M14 bolts, or something of a similar size, and slide the clamp back on to securely close off the hose. Do the same thing with the lower hose. Here's what I mean:


    (NOTE: there is maybe 1/4 cup of coolant in the TB--it's going to spill, no matter what) Set the TB aside for now. Here are some pics of the throttle body removed to help visualize where these hoses are, and how the throttle cable comes out:

    front side

    rear side

    3 d) The EGR valve is located on the underside of the TB flange on the intake manifold. There are two 12mm bolts holding it in--the heads are facing straight down. Remove these bolts, and remove the EGR valve, being careful to catch the thin metal gasket that comes off with it. Set this aside for later as well--if you get frustrated trying to loosen the motor mount cross-bolt, you can take a break and clean the EGR valve then ;)


    4) Now the only thing that stands between you and the motor mount is that big black wiring harness. There are two nuts securing it to the firewall, one on top and one on the underside. The top nut comes off pretty easily with just a 10mm socket. The bottom nut is a bit trickier. Feel around a bit and you'll find it. After some futzing around, I was able to get it off pretty easily with a 10mm socket (deep socket WON'T work), connected to a U-joint, and a skinny 3" extension (1/4" drive is the only thing small enough to get in there).


    Slide the wiring harness off so it's just hanging loose. In order to get at the rear-driver side nut on the motor mount, you'll have to bend the bottom stud, that secured the wiring harness, out of the way. I stuck a 7mm deep socket onto a 3" extension, then just slide the socket over the stud and was able to easily bend the stud by hand, with the added leverage.


    5) I've been putting it off as long as possible, but it's about time we have to deal with it--the long bolt that goes horizontally through the motor mount to secure it to the engine. The head of the bolt is on the driver's side, and the nut is on the passenger side. Unlike the front mount, the bolt is free to rotate inside the mount, which complicates things a bit. Your best bet is to attack the nut (passenger side). Spray the nut liberally with some liquid wrench and let it penetrate for awhile. (Maybe this would be a good time to clean out the EGR valve and throttle body?)



    6) As you can probably see by now, there is virtually no room to get a wrench in there to turn that nut, and it's on there TIGHT, so this is where things get a little tricky. I was able to jack my car up and get at the nut pretty easily from under the car, but, I have an aftermarket catless midpipe, so I had a lot more room to work than someone with a stock exhaust setup. I have no way of knowing if you can reach it from below the car, so I'll tell you how I was also able to reach it from above. I used, in this order, a 17mm socket, U-joint, 12" extension, 6" extension, all 1/2" drive. (Don't even think about using a 3/8" set--you'll probably break something.) If you thread it through all the junk below the intake manifold this long extension should come out on the passenger side of the intake manifold, angled slightly upward. If you have access to an impact wrench, you'll probably have this thing off in no time. Otherwise, use your breaker bar, or a sturdy 1/2" ratchet, and turn that little bastard with all your might--but be careful because with that many extensions, you don't want the socket to slip off the nut and round the corners. You might find that instead of the nut loosening, the entire bolt just rotates. If this happens, stick another 17mm socket and wrench on the other side of the bolt--it'll hit something in the engine bay and hold itself in place while you loosen the nut. Slide the bolt out of the mount, along with the metal bushing, and that rubber coated metal plate dealy.

    The 3 nuts that secure the mount to the frame can be removed using a 17mm socket (not a deep socket!), a U-joint, and a long extension--I used a 12" and 6" extension together. Now just wiggle the mount out of there, and you're ready to start putting shit back together again!

    See if you can guess which one you just took out, and which one you're about to install ;)

    Cleaning the EGR valve (optional)

    7) There are 4 long phillips screws that hold the solenoid onto the valve itself--remove those screws. Set the EGR valve on some towels and spray brake cleaner liberally into both ports, working the valve back and forth, until the runoff is clear. Put a bit of oil on the valve shaft and spring, and reattach the solenoid unit. You'll probably want to let it sit and drain for awhile since brake cleaner takes awhile to evaporate.




    8) Everything goes back together exactly as it came apart except in reverse order. I'd like to toss in a few notes though:

    When putting the new mount in, thread the 3 nuts that hold the mount in place down, but don't tighten them until you get the long bolt through the mount. I had to use a jack to lift the engine up about 3/4" in order to get the holes in the bracket and mount to line up. Position the jack as far back on the engine/transmission as possible if you need to lift it to get the bolt in. It helps to have a bolt that is slightly smaller than the mount bolt, that you can use to tell how close the mount and bracket holes are lined up, since there is very little visibility down there. Make sure you put the bushing and that metal/rubber plate back onto the bolt before you put it back into place.


    When reinstalling the EGR valve, the pointy tip of the gasket goes toward the back of the valve--the blunt side goes to the front.


    When you get to the throttle body, make sure you scrape all of the old gasket off both sides of the flange. Mine was pretty much fused to the throttle body around the bolt holes, and took a lot of scraping to remove--but if you leave don't get it all off, you run the risk of having a vacuum leak when you're done. Then you have to start from scratch with the gasket. If you don't have a new gasket, use some RTV gasket-maker. I'd also recommend to hook up the lower coolant hose to the TB before re-attaching the TB--otherwise it'll be nearly impossible to reach.

    Initial Driving Impressions

    I previously installed the SU front mount, so all these impressions are coming from an engine with a fully worked-in front mount.

    Startup: A nice "thruh-duh-duhm" greets you when you turn the key. You can really feel the engine turning over, and I like it!

    Idle: I can't comment accurately on this, because I seem to have a fair vacuum leak at the TB (gotta redo that gasket), so it runs pretty rough at idle. I'll add to this spot once I get that fixed. EDIT: Now that I've got the vacuum leak smoothed out, I can say that idle is a bit bumpy, but nothing that really shocks me. As long as you've got a nice steady idle, you can just pretend you're getting a shiatsu massage at stoplights!

    Starting/stopping: The drivetrain feels nice and solid! I haven't had a chance to test out wheelspin, but I have a feeling it would be non-existent. My clutch feels a bit grabby, but there's very little engine lurch if you do make a rough start. There's a lot of vibration between 1000-1200rpms, so I'm adjusting my clutching technique to feather it out around 1500rpms. Quite a bit more noise is transmitted through the cabin during acceleration--it actually changed the sound of the engine quite a bit, at least as I perceive it from inside the car.

    Shifting: Shifts--both up and down--are clean, crisp and completely devoid of drama.

    Cruising: Vibration and cabin resonance is very noticable. Definitely have to turn the radio up a few clicks higher to listen at the same percieved volume. I have a feeling this will settle itself out over time, as these mounts tend to do.

    Long-Term Impressions

    I'll get something in here in a few hundred miles or so, once the mount gets fully broken in.
    Last edited: Jul 9, 2007
  2. micahlarson

    micahlarson Guest

    tell me what you think and how it feels when your done!
  3. AJ

    AJ 110 HP of FURY!

    Wow, great write up! I'd like to put this on the main website if that's ok. Is this for all years MS Protege?
  4. dmention7

    dmention7 Hater

    Thanks AJ! You're more than welcome to post this wherever you'd like.

    And yes, this should be good for all MSP's. The basic steps should also be accurate for any 3rd gen protege. I believe the only major difference would be that it's a plain old air hose, and not an IC pipe that's attached to the TB. Oh, and no strut bar to remove.

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