you feeling a weird vibration from your car when you shift or accelerate? Is
the shifter rocking back and forth like itís possessed? Are you hearing
and feeling a huge knocking noise when you drive? All these are a symptom of
old or broken motor mounts. In this tech article I will go over the steps
involved with replacing the motor mounts on the BMW E36 3 Series from
1992-99. A lot of people have been asking me to do an article on this
subject, so here goes.
mounts have two primary functions in a car. One, they secure the motor to
the vehicles chassis, and prevent the motor from crashing into the fenders.
When you hit the gas, the torsional forces of the crankshaft turning causes
the motor to twist as it delivers power to the rear wheels. The motor mounts
prevent this. Unfortunately, bolting the motor direct to the chassis also
results in transmitting the vibration from the engine all throughout the
car. The solution is to mount the engine to the chassis using rubber mounts.
The rubber acts as a damper, allowing the engine a certain amount of play,
and keeps it from rattling you to death as you drive.
time, the rubber mounts begin to wear out due to constant vibration, the
torque of the engine twisting the mounts, and general road grime and oil.
Eventually the rubber will rip or fail, causing the motor to twist
excessively. The fix for this is to replace the mounts.
first step in replacing the mounts is to first determine the location. Open
the hood and look down on either side of the engine. You will see a rigid
metal link that bolts to the engine block on either side. At the end of
these links is a rubber spacer. The spacer is the motor mount.
a good idea to disconnect the battery at this time as well. We will be
working around the general area of the starter motor, and it is possible to
accidentally touch the terminals with a wrench. I have seen wrenches welded
to starter motors because someone forgot to disconnect the battery.
chock the rear wheels and jack up the front of the car. Be sure to secure
the front end on good quality jack stands. NEVER rely on a jack to hold the
car up. You are asking for trouble. For those of you not familiar with how
to jack up the front of your car, I highly recommend you check out Wayneís
article on jacking up your BMW. Here is a link for the article.
the front end is up on jack stands and is firmly supported, we can move onto
the next step. Look under the car for the nut that secures the motor mount
to the chassis. Remove each nut from either side. Donít worry about the
motor falling or shifting at this point, as the weight of the block will
keep it supported in place. Now,
we will want to remove the upper nut on each of the mounts. You may find it
easier to access these from inside the engine compartment.
comes the tricky part. We will want to actually jack up the engine enough so
that we can pull the old mounts out. The best location to jack the engine is
from the oil pan. Get a piece of wood about a foot long by 6 inches and
place it in between the jack and the oil pan. The wood will help distribute
the weight of the engine and help prevent you from damaging the oil pan.
start jacking the engine up. Go very slowly and look for any hoses, lines or
wires that may be stretching. If you see any of this, STOP, and address
whatever may be stretching. Now keep jacking just until you have enough
clearance to pull the old motor mounts from between the engine and the
chassis. BE EXTREMELY CAREFUL when doing this, as the engine will only be
supported by the jack. In some cases it may be helpful to put jack stands
under the wood while the engine is up. This will provide extra safety.
the old mounts are out, slide the new mounts into position on the chassis.
Now slowly lower the engine until the threads on each mount slide into their
respective holes on the engine link. It may take some time to get these
lined up exactly. Once lined up, lower the engine completely so that the new
mounts are bearing the load from the weight of the engine.
remove the jack from under the car and thread new self-locking nuts onto
both sides of each mount. Itís important to always use new nuts as they
are designed to only be tightened once. If you re-use the old nuts, they can
slowly work themselves loose and possibly cause a huge disaster.
Once all the nuts are threaded on, torque them to 30ft./lbs.
Now jack the sides of the
car up and remove the jack stands. Lower the car back down to the ground.
Well, there you have it - it's
really not too difficult at all. If you would like
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