In this continuing
article on rebuilding your E30ís suspension, we will focus on replacing
the rear trailing arm bushings on my 325is. This is a more complex job for
the amateur mechanic, but as with all things, with the right tools and
information, you can do the job yourself. Keep in mind that this article
applies to all E30 models, however the early 318i models from 1984-86 use
rear drum brakes rather than discs. This article also applies to the E36
318ti models from 1995-99. In order to keep costs down, BMW used the same
rear suspension from the E30 on the 318ti.
tech articles are written with the home mechanic in mind. For the most part,
these articles require nothing more than a decent set of tools, including a
good metric socket set and ratchet. It is also well worth the money to
invest in the following tools. First, a good quality vernier click style
torque wrench. You will need this in order to make crucial tightening
torques when working on suspension bolts and nuts that are under extreme
loads. Next and most crucial, a good set of jack stands. Try to get some
high quality ones that have a sturdy construction and donít look too
flimsy. Usually you can get a set for around
replace the trailing arm bushings? Over time, these small bushings get
subjected to a lot of wear. They are the primary support point for the
suspension pivot. Many times a worn out bushing will give your car
unpredictable handling characteristics, as well as an incorrect rear wheel
camber. Just remember, rubber dries out over time and can start to crack.
Often this is what causes these bushings to wear out.
replace the bushings, we will need to remove the trailing arms from the car.
In order to that we must also remove the drive axles from the car. To begin,
we will need to first pry the center caps off the rear wheels while it is
still on the ground. Now look inside, you should see the drive axle
retaining nut. No w we will need to loosen this nut. Loosen the nut with the
car on the ground. This will help you gain enough leverage to get it off, as
it is torqued in excess of 150 ft/lbs. In many cases, it may be easier to
simply use an impact wrench. Get the nut loose but do not remove it.
Be sure to use plenty of penetrant spray such as WD-40 while
loosening the nut. This will prevent stripping or seizing.
letís jack the car up. First, chock the front wheels to keep them from
rolling while you have the rear wheel jacked up. Next, loosen (but do not
remove) the rear lug bolts. Now, use a floor jack and jack up the rear of
the car. Be sure to jack the car up on enforced part of the body, such as a
crossmember or chassis beam. Be sure not to jack the car up on any other
part, as you could put a hole right through the bottom of the car. I have
seen Porsches in the past where jacks have punctured the floor boards. A
handy reference is Wayneís article on jacking up your BMW.
Once the car is firmly secured on jack stands, the next step is to
remove the lug bolts on the rear wheels and take the wheels off. Now, look
at where the drive axles are bolted onto the differential. There are six
Allen head bolts that hold each axle to the differential. Before you remove
them, itís a really good idea to clean them off to get any dirt of grease
out of the bolt heads. Any good brake cleaner should work perfectly. We
donít have to get them spotless, however just enough to where we wonít
have the Allen key from popping out. Itís also a good idea to hit the
bolts with WD-40 or good penetrating oil. Typically, I like to let the spray
sit overnight, to let the oil work itself into the threads. This will make
it much easier to remove the bolts, not to mention preventing stripping and
seizing when you hit them with the wrench.
use an Allen head socket and remove the 6 bolts on each side. The drive
shafts will now be free of the differential. Use some wire or rope to hold
the shafts up; otherwise they will just hang down free and put stress on the
back to the brake rotors, and remove the driveshaft retaining nuts and the
lock plates underneath. Now, bolt a puller to the rotor face using the lug
bolts to hold it on. Now use the puller to push the driveshaft flange out of
the rotor/hub on each side. Have a helper hold the drive shafts when you do
this. Keep pushing with the puller and the driveshaft will pop out. Now
remove the wire supporting the shafts and set them aside.
is a good time to inspect the rubber CV boots. These boots are used to hold
grease, keeping the CV joints lubricated. If there are any tears or cracks
in the CV boots, replace them.
the drive axles now removed, now we can focus on the steps involved to
remove the rear trailing arm. First, Look the rear brake calipers.
Disconnect the brake wear indicator sensor on the passenger side and also
the ABS speed sensor connections. Now find the brake hose and trace it back
to itís connector on the trailing arm. Because of the way the hose fits
into the mounting bracket, we will need to disconnect the brake lines.
First, open the hood, take off the brake reservoir cap and place a small
piece of cellophane over the top. Now put the cap back on. This has the same
effect as putting a straw into a glass of milk, then putting your finger
over the top and lifting the straw out. The milk stays in the straw. When we
disconnect the brake lines, the cellophane will help keep the brake fluid in
the lines, and not spilling all over the floor. Undo the fittings on the
trailing arm and plug the brake line to keep fluid from spilling out all
over the place. Now look under the control arm and locate the two 13mm nuts
that secure the sway bar end links to the trailing arms. Just remove the
nuts. As you lower the trailing arm they will automatically withdraw from
place a jack under the trailing arm assembly to support it. Loosen and
remove the lower shock absorber mounting bolt on both sides. Now, slowly
lower the jack. The sway bar end links should automatically withdraw from
the trailing arm. Now have a helper stand on the trailing arm to further
lower its angle. Now remove the coil spring from the car. By lowering the
trailing arm, we are now able to access the trailing arm mounting bolts in
the front. Remove these bolts and remove the trailing arms from the car. You
may need a helper to support the rear of the trailing arms while removing.
you will need to take the trailing arms to a competent machine shop to have
the old bushings pressed out, and have the new ones pressed in. This should
not be more than $30 at any shop. You can press the bushings out yourself,
however without use of a hydraulic press, you may find this difficult.
the bushings are in, get the trailing arms lined up to the brackets on the
rear axle carrier, and have a helper hold it in place. Now slide the
mounting bolts back in place and torque them to 30ft./lbs. Now, place the
coil springs back in the car, making sure the rubber retaining pads are
lined up correctly. Now, rotate the control arms upward, making sure that
the sway bar end links slide into the mounting holes while the arms move up.
Now use a jack to support the trailing arms and re-install the lower shock
absorber mounting bolts. Torque them to 60 ft./lbs. Now, put new
self-locking nuts on the bottom of the sway bar end links and torque to 17
ft./lbs. Now reconnect the brake line fittings. Reconnect the brake wear
indicator and ABS speed sensor connectors at this time as well.
lube the outside shaft of the driveshaft and push them back into the
trailing arm hub. Clean the threads of the flange really good and oil the
threads. Now slide the new lock plate on and thread the retaining nut on
finger tight. Now re-install the 6 Allen head bolts that hold the drive
axles to the differential. Make sure these bolts are clean before
re-installing and use a small dab of Loc-tite on the threads. This will help
to keep the bolts from backing out. Now use a criss cross pattern and torque
each bolt incrementally first to 20 ft/lbs, then one more time to 46
we are ready to bleed the calipers. In this instance, we will assume that
you have a helper to do this. First, loosen the bleeder screw on the
caliper, then quickly snug it back up, we want to just get it loose, not
remove it. Next, get a jar and fill it about halfway with fresh brake fluid.
Place one end of a clear plastic hose over the bleeder screw and run the
other end into the jar.
open the reservoir cap, remove the cellophane and check the fluid level. Top
it up as needed. Leave the cap off, as this will help to draw fluid through
the system. Have your helper pump the brakes until pressure begins to build
up. Then have your helper step on the brakes to hold the pressure and open
the bleeder valve for about 1 second then quickly close again. You will see
fluid flow through the hose with a lot of air bubbles in it. Having the hose
in a jar of brake fluid prevents air from flowing back into the caliper.
Again, have the helper again build up
pressure on the brakes and hold the pedal down. Open the bleeder valve for
about 1 second then quickly close. You will want to repeat this step until
there are no more bubbles flowing through the line.
As the air is bled from the lines, it will take less time for the
brakes to build up pressure. Check the fluid level in the reservoir while
your helper is pumping the brakes to build up pressure. Do not let the
reservoir run dry or you will have to bleed all over again.
the lines are bled, clean up the area around the caliper. Use the brake
cleaner to get rid of any extra fluid around the area. Once clean, remount
the wheels, install the lug bolts snugly, but do not tighten yet. Now jack
the rear of the car up again and remove the jack stand. Now lower the car.
Be sure to do this one side at a time. Now simply tighten the lug bolts in a
we need to torque the drive flange retaining nuts. Having the wheels on the
ground will help you torque the nuts down. With the car in the air, you risk
knocking the car off the jack stands. We are going to torque these nuts to
150 ft./lbs. Thatís a lot of torque! You may need an impact wrench to get
it there. Once torqued, just re-install the center caps and take the car for
a spin around the block. You should notice a stiffer feel from the rear. And
the handling should be tight and responsive.
Well, there you have it - it's
really not too difficult at all. If you would like
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