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NA

Engine - Motor Mount Replacement

Majority of these instructions taken from Mk1Maddness on a Miata.net post. Included some of my own personal experience, as well, from having done this job last weekend.

Tools Needed

  1. Hydraulic jack (long enough to slide under car beneath oil pan when the car is up on jack stands or a lift)
  2. Small block of wood to place between metal of jack and oil pan
  3. Jack stands or ramps
  4. 10, 12, 14 mm sockets and wrenches
  5. Universal socket joints
  6. About 2 feet of socket extensions
  7. Torque wrench
  8. Cheater bar definitely helps
  9. Bench vise (or a friend to hold onto the mount bracket)
  10. New motor mounts
  11. Penetrating oil

Torque Specs

All nuts 42-58 ft-lbs
All bolts 27-38 ft-lbs

Instructions

Some of the below steps are not strictly required to complete this job. I've made note of them below by marking the steps as Optional.

  1. Loosen the lug nuts on the front tires. They will be removed once you jack the car up to give extra room to work.
  2. Place the car on jack stands or a lift. I prefer jacking both front and rear and using 4 jack stands. Later on you will need to use the jack to lift the motor slightly, and I liked doing this from a level car.
  3. Optional: Remove the stock air intake box and tubing (if you have it). Make sure to remember to take the O2 sensor out. You can still remove the drivers side engine mount without removing the air intake box, but more room to work is also a good thing. Take your pick.
  4. Optional (but recommended): Remove the exhaust manifold and down pipe. My stock exhaust is old and rusted, and was not being very cooperative on the day I did this. You can technically swap the motor mounts without removing the exhaust - I'll talk about that down below.
  5. Under the car, loosen BUT DO NOT REMOVE the 14mm nuts located on the subframe, which connect the motor mounts to the subframe. These sit inside a recessed hole near the rear of the lower control arm. An extension would be useful here. Leave the nuts on the stud with a thread or two showing.
  6. Place your hydraulic jack under the oil pan with the block of wood between the metal of the jack and the oil pan. The goal is to distribute the force against the oil pan and not crack it. Ensure that the wood does not contact anything other than the oil pan. If the wood will contact any part of the subframe, you'll be lifting the car and not the engine.
  7. SLOWLY begin jacking the engine up, and watch to ensure nothing from the rear of the engine contacts the firewall. On my 1.6 NA, I got away with simply unplugging the CAS and jacking it up. On my 1.8 NA, I needed to disconnect the coil pack from the rear of the engine (two bolts on top connected to the valve cover, one bolt on the bottom which is a pain to get to and much easier to remove with a ratcheting box wrench).
  8. Continue to jack up the engine until the mounts come away from the subframe. On one car I did, this made a rather loud popping sound. On another, I barely heard a thing. To give yourself as much room as possible to work down below, continue to raise the engine, but be careful the nuts you loosed in the previous step do not catch the subframe and begin lifting the car.
  9. Passenger Side Mount. With the engine up, move into the passenger side tire well. Look straight in towards the engine and you will see the motor mount connected to the engine. The metal "cup" that the rubber mount sits in should be loose if you go to shake it by hand. If not, give it a whack with a breaker bar; it should wiggle a bit.
  10. Remove the 14mm nut connecting the mount to the subframe. A washer should come with it.
  11. Remove the 14mm bolts holding the mount to the engine block. On the passenger side of a 1.8 NA there are FOUR (4) bolts (one on the upper right of the mount connecting to the alternator). Multiple extensions will help you greatly here. REMEMBER which bolt goes where! They are of different lengths.
  12. With the bolts and nut removed, the mount is now free. The metal "cup" that the rubber mount sits in has the stud through it and the subframe. Wiggle the mount around until the stud comes out of the hole in the subframe and until you have enough clearance to remove the metal "cup". I found it much easier to get the mount out without the metal "cup" attached to it.
  13. Remove the motor mount assembly from the engine. I find it easiest to pull the mount out underneath the car. Note that it has three components: a metal "cup", a metal bracket which bolted to the engine, and a rubber mount which is connected to the metal bracket with a stud and nut. Despite the simplicity of saying "remove it", this can require a few minutes of reorienting the mount until it fits out in the space provided. Remember how you got it out, so you can reverse the procedure when putting it back in.
  14. Place the motor mount bracket in a bench vise, or have a sturdy friend pin it down. Note the orientation of the rubber mount as you remove it. Now remove the nut holding the rubber mount to the bracket. Once you remove the old mount, attach the new mount in the same way; there should be a bump on the new rubber mount so that it fits in only one orientation.
  15. Torque the rubber mount to the bracket, 42-58 ft/lbs.
  16. With the bracket assembly back together (but no "cup" yet), insert the bracket and mount back into the engine bay. Then slide in the "cup". Then get the assembly back into the subframe and lined up with the engine block.
  17. Unless you're lucky, the holes on the bracket will not line up perfectly with the bracket. The new rubber mount is not as compressed as the old one. I started by getting one hole lined up, putting in the bolt hand tight, but loose enough so that I could still move the bracket. Line up the next hole and continue. A universal joint on your socket will also be very useful here.
  18. You will reach a point (I did) where the last hole just does not want to line up and you cannot thread the bolt into the engine block. My bracket was too high, and the motor needed to come up to make the holes align. To get this alignment, lower the engine slightly so that the stud on the mount passes through the subframe and you can thread the nut and washer back on. Get the nut back on securely (this side of the car ONLY), and then jack slowly back up. This will pull the mount down against the engine, and you should be able to line up the last hole or two.
  19. With all the bolts back in, remove the nut on the passenger side subframe stud and torque the bolts down to 27-38 ft/lbs. Do NOT add back or torque down the subframe stud nut and washer.
  20. Driver Side Mount. Similar to the passenger side mount. Follow the same steps as above, but with a few caveats:
  21. If you did not remove the exhaust manifold and downpipe, you probably will not be able to remove the driver side mount and bracket assembly. You can wiggle it enough to get the "cup" off, but I was unable on my 1.8 NA to get the full thing out. By properly turning and bracing the mount in the engine bay, I was able to use a socket to remove the old rubber mount and torque on a new one.
  22. If you did remove the exhaust, you should have enough room to remove the mount and change the rubber mount on the bench vise.
  23. Once you've got the driver side bolted back on and torqued to the block (27-38 ft/lbs), lower the engine back down.
  24. Reinstall the washers and nuts on the subframe stud, and torque to spec. 42-58 ft/lbs.
  25. With the full weight of the engine on the mounts, check the torque of all bolts and nuts.
  26. Reinstall any various bits you removed from up above. Exhaust, coil pack, etc.
  27. Go for a drive and check your work. If you switched to higher durometer mounts, you may have additional noise and vibration in the cabin.
  28. After a quick ride, it wouldn't hurt to check the torque of all nuts and bolts again (probably not the nut on the inside of the bracket mount, which is now inaccessible, though).

If you can't get the bracket holes lined up

As I mentioned above, if you cannot get the bracket holes lined up DON'T FRET. Make small adjustments to the height of the engine with the hydraulic jack. In my experience it takes almost perfectly alignment between the block and the bracket to get the bolt to begin threading. Don't rush and risk a cross-threaded bolt.

Even having done this a couple times before, I spent 15-20 minutes per side getting things aligned and the bolts back in. Sometime it goes smoothly; sometimes not.

End Notes

Despite this job only involving a few nuts and bolts, the areas you're working in are quite confined and can be annoying. Take your time. This job might require a few hours, but it will leave you with a great sense of pride and satisfaction when it's complete.