cyclopticgaze

bmw 2002

Fixing a Crooked Motor

Jul 13, 2008

     One of the biggest problems holding the car back from being drivable was that the engine was improperly aligned.  The passenger side of the engine was too far forward, and the fan dug into the radiator.

     Both motor mounts and the transmission mount are shot.  They're made of rubber, and if I've learned anything, it's that "if it's rubber, it's broke."  So, I ordered up new mounts from Ireland Engineering.  Rather than rubber, these parts use polyurethane.  Urethane is much stiffer than rubber, so noise and vibration will make the car's interior louder and rougher.  But I went with urethane because it's supposed to withstand oil better than rubber, hopefully extending the life of the mounts.


The fan spins with the engine and has dug into the radiator.  A front end collision can push the radiator into the fan, but that's not the case here;  the engine has pushed too far forward.

radiator eaten by the fan


     There are two rubber motor mounts that bolt the engine to the car's body.  Further back, there's a single rubber mount that attaches the transmission to the car.  The rubber is meant to absorb the vibration of the engine, but it's gone bad over the years.


Of course, if you want to detach the motor from the body, something has to hold it up.  This shop crane did the trick.

engine hoisted by the shop crane


Here's the right (passenger's side) motor mount.  The engine sits at an angle and this mount bears most of the weight.  The curley-que piece of metal stops the engine from sliding very far forward and is probably what has kept the radiator from being completely chewed by the fan.

old right motor mount


The right motor mount from down below, with the engine slightly raised.  With the curley-que stopper out of the way, this mount doesn't look too hot.

old right motor mount


Here's the right motor mount off the car.  Rather than remove the mount, I just unbolted the bracket that attaches it to the block.  The mount is cracked and soaked with oil and it really shouldn't bulge like that.

old right motor mount removed


Alright, so I cleaned and painted the bracket and here's the new motor mount attached to the engine.  I just need to slide the curley-que piece underneath it and drop the engine into place.

new right motor mount


     Ah, but that would be too easy!  When I lowered the engine, the motor mount wouldn't properly line up with its perch, so I couldn't get the bolts into it.  I kept pushing and shoving on the engine, but it wasn't enough.  I could swing the engine side-to-side pretty well, but the problem was that the engine sat too far forward, and I couldn't force it back.


So here's the solution.  With the engine hoisted just a little by the crane, I supported the transmission and differential with bottle jacks and loosened all the bolts on the drivetrain.  I completely removed the tranny mount (I'm replacing it anyway), then loosened the center bearing that supports the drive shaft and the six bolts that support the differential in the back.

jacked-up drivetrain


And it worked!  With the whole drivetrain loose, I was able to push backwards the engine and feed through the bolts.  Here, I just need to lower the engine a little more and tighten them.

new right motor mount attached


All tightened down, with LocTite on the threads for a little more security.  Before and after.

right motor mount before right motor mount after

Alright, with all that drama out of the way, let's do the left motor mount (on the driver's side).  Here's the stock mount.  It's kind of an odd shape, and it doesn't support as much weight as the right motor mount.  That open hole to its left is where the oil dipstick goes.  I pulled the whole thing out to give me more working room.

old left motor mount


I pulled the left mount and, oh look, it's cracked!  The crack let the two bolts easily pull away from each other, severely compromising the mount's ability to stabilize the engine.

old left motor mount removed


With the right motor mount properly set, it didn't take too much muscle to get the left one here lined up properly.  I bolted the one side of the mount to the engine, then a few yanks on the crane's chains and the other side of the mount slid into it's perch on the car's body.

new left motor mount


With the engine set nice and tight to the car, I worked my way backwards.  Here's the transmission mount.  I've lifted the transmission up and you can see that the tranny mount is completely sheared in two.  It bolts to the tranny on top and to a support cross member below.  I suspect that this mount has been broken for a while and allowed or facilitated the engine's misalignment.

old transmission mount


The new transmission mount is a little beefier, which is good because the stock mount really is too small.  That's clear here because the old mount shouldn't be in two pieces.

old and new transmission mounts


I had to raise the transmission all the way up and loosen the cross member almost all the way off in order to get the new mount into place, but then it went in well.  The engine and transmission are still slightly crooked, but only by less than ~1/8 of an inch back here at the transmission mount.  The urethane bulges a bit when the nuts are tightened down, but it's a big improvement over using the stock part.

new transmission mount


With the transmission mount set, I again worked my way back and tightened the center support bearing and the differential attachments.  The whole drivetrain is nice and tight and the engine's fan now has clearance from the radiator.

fan doesn't eat the radiator any more


     Phew!  Glad that's done.  One more step towards getting the car drivable.