Replace all 4 motor mounts on 1990 Deville 4.5L V8

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Cadillac Tech Tips - How to fix it Discussion, Replace all 4 motor mounts on 1990 Deville 4.5L V8 in Item Specific Cadillac Discussion; ...
  1. #1
    eddie262 is offline Cadillac Owners Member
    Automobile(s): 85&88 SEVILLES, 90 DEVILLE'S (2)
    Join Date
    Jul 2008
    Washington DC metro area

    SmileReplace all 4 motor mounts on 1990 Deville 4.5L V8

    Replacing the motor mounts on a 1990 Cadillac Deville with 4.5L V8

    The tools, techniques, and strategy detailed below should be considered a GUIDE only. You situation may require a different approach.

    Lifting points:
    The 4.5L V8 has 3 factory-installed lift eyes. Both rear corners and the driver side corner near dipstick.

    For the right front lift point (passenger side front) you can remove the upper 15mm bolt from the power steering mounting bracket and then bolt on a temporary lift eye or bracket.

    Factory service manual
    engine hoist (I used the hydraulic kind traditionally used for pulling V-8s out of rear wheel drive cars.)
    engine sling with screw-drive adjuster and big hooks at the ends of the chain.
    13mm and 15mm sockets (3/8 drive)
    12mm and 15mm swivel sockets (3/8 drive) (got mine from Sears)
    15mm deep socket (3/8 drive)
    10mm, 13mm and 15mm flex head ratcheting wrenches (I used Gear Wrench brand)
    15mm box/open end wrench, long shank (I have a set of long wrenches I got from Harbor Freight for $22)
    various socket extensions 3" to 10" long (3/8 drive)
    threadlocker (blue)
    brake cleaner
    WD-40 or other spray lubricant
    various blocks of wood
    flat bladed screwdriver (long shank)
    The Kreepster mechanic's creeper (
    The Kwiklift (

    If possible - actually you HAVE TO raise the car in the air so you can use a creeper to get under it.

    Setup: You may choose to raise your car however you like - this is how I did it.

    1. Car on Kwiklift facing the back end of lift (where the Kwiklift lifting tube is located.)
    2. Parking brake on.
    3. Disconnect battery.
    4. Jack up Kwiklift and place stacked 4x4 lengths under the ramp ends to raise the ramps 8 inches off the floor.
    5. Position the engine hoist with its forward legs in the space between the ramps.
    6. Rotate the lifting tube rearward so that it's center section faces the base of the engine hoist, and tightly shim the space between the hoist and the tube with wood blocks to prevent the hoist from rolling forward when placed under load.
    7. Positioning the hoist in this manner allows you to adjust the hoist upward simply by reaching behind your head and pumping the handle.
    8. When installing bolts to the holes in the engine block, it is usually easier to hand start each bolt first, slightly adjusting the engine hoist up or down as needed to line up the bolt holes in the brackets with the holes in the engine.
    9. Remember: the aluminum engine block WILL NOT TOLERATE any amount of cross-threading – so the ability to minutely adjust the engine height is important!

    Engine mount replacement

    I suppose it doesn't matter what order you follow, but here's the order I used.

    Right rear (passenger side transmission mount)
    No need to remove the mounting bracket off the transmission,
    Undue the nuts securing the mount to the bracket and the two nuts securing the mount to the frame.
    Use the engine hoist to lift the engine clear of the studs on top of the mount and swap in the new one!

    Left rear (driver side transmission/engine mount)
    Remove the 3 bolts holding the mounting bracket to the engine block. Top bolt may hang by a thread until you lift the engine - then it should fall clear.

    Remove the nuts securing the mount to the frame.

    As the factory service manual recommends, remove the 5 bolts securing the steering rack to the cross member. The lowest bolt threads into a welded on nut - DO NOT try and remove the nut - big problems if you do that!

    The steering rack bolts have threadlocker on them - they will be very stiff and hard to turn but they will come out! I put blue threadlocker on my bolts when I reinstalled them.

    Use the engine hoist to lift the engine.

    As the factory service manual recommends push the rack up and forward and maneuver the mount out.

    Transfer the bracket to the new mount.

    When installing the new mount, install the 3 bracket bolts first, starting from the top, then the bottom 2 nuts.

    Reinstall the steering rack - all 5 bolts! You may want to use threadlocker. The Factory Service Manual has a note about threadlocker on these bolts.

    OK, 2 down and 2 to go!

    Left front (driver side transmission mount)
    Remove the 3 bolts holding the mounting bracket to the engine block. Top bolt may hang by a thread until you lift the engine - then it should fall clear. Note that the bolts also locate and secure a sheet metal bracket for the oil cooler lines.

    Remove the 2 nuts securing the mount to the frame.

    Use the engine hoist to lift the engine.

    Remove the mount and transfer the bracket to the new mount.

    Place the mount into position, and install the 3 bolts securing the bracket to the engine. Then install the 2 lower bolts. You may need to move the engine up or down to get all the holes to line up.

    Right front (passenger side engine mount)
    Disconnect the battery if you haven’t already.
    Remove the brace that runs from mount to engine block.
    Remove the topmost cable from the starter solenoid to give you more room to work – you’ll need it!
    Remove the wire from the AC clutch to give you more room to work.
    Remove the stud from the right side of the bracket to engine block.
    Remove the 2 bolts securing the rear of the AC compressor bracket to the engine block (one is 13mm and the other is 15mm)
    Remove the 3 bolts from the front face of the AC compressor (2 of them screw into the compressor’s mounting bosses and the other screws into the engine block). You’ll need to pull away the plastic shroud in the right front wheel well – I didn’t have to remove it, just pushed it out of the way.
    With the compressor loose, remove the 10mm bolt that secures the water pipe running behind the AC compressor.
    Remove the clamp securing the water pipe under the car and remove the clamp securing the water pipe above the AC compressor. Coolant will drain out so have a catch pan ready!
    Remove the water pipe from the engine.
    Wedge the AC compressor toward the passenger side of the car.

    If your right-handed, put your left hand up between the oil pan and the BACK of the front cross member – you can then FEEL the nut that is hard to reach and out of sight from the front of the car.

    Using a MAPP gas torch, I bent a cheap 15mm wrench into a U shape (sort of), and was able to place the open end of the wrench on the nut with my right hand and used my left index finger to help seat the wrench on the nut. It isn’t a perfect arrangement and the wrench can slip off the nut because it’s gripping the nut at an angle, but it worked. I was able to slowly loosen the nut and remove it.

    The front nut securing the mount to the bracket is much easier to access and didn’t require any special tools.

    Remove the 2 nuts securing the mount to the frame.

    Use the engine hoist to lift the engine.

    Remove the mount and transfer the bracket to the new mount.

    You may want to loosen or remove the nuts securing the left front mount to the frame in order to raise the engine high enough the get the new right front mount installed.

    Place the mount into position; reverse the steps to complete the installation!

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  3. #2
    Moondoggie is offline Cadillac Owners Member
    Automobile(s): '70 Eldorado '96 SLS 2001 ESC
    Join Date
    Sep 2005

    Re: Replace all 4 motor mounts on 1990 Deville 4.5L V8

    Alternate procedure for RF engine mount, still head banging difficult but without having to custom bend a wrench.....

    The patient was a '92 4.9 SDV.

    I used a bottle jack and a block of wood to support the oil pan. Unbolt the A/C compressor from the compressor mount and tie up the compressor with a wire coat hanger as far up and toward the radiator as possible. Remove the bottom engine mount to cross bar nuts and slightly raise the engine to relieve the weight off the engine mount. The rear compressor bracket uses two 40 Torx head bolts to the compressor and two 13 mm bolts to the compressor mount. Unbolt the six 15 mm bolts securing the compressor mount to the engine block and the one 15 mm stud through the engine mount bracket. The engine mount AND the engine mount bracket are now free. Raise the engine enough to clear the bottom studs and bring out the impacted tooth. Unbolt the bracket from the engine mount and install on new engine mount. Install new mount. Book time is hours, make it three times as long working in the driveway on your back with a greasy mess. I would also recommend hardened impact 13 and 15 mm sockets.

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