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 Removing
Troublesome Brake Drums
©2004
Eric Neyerlin - ZPARTS.COM
Quite
often drums can become rust & corrosion bonded between the inner backside
of the drum and the cast iron hub surface leading to major difficulties
when removing the drum for service. If gentle tapping and rocking of the
drum back and forth does not lead to removal, try some of the approaches
listed below.
Approach One: First, jack up
your car and place it on very solid jack stands, remove the wheel and
screw the lug nuts back onto the studs enough to protect the threads while
working. Keeping in mind that Nissan drums are made
of aluminum and hence, prone to permanent warpage and chipped fins, try
these 2 steps in this order.
Step 1 .
Gently use a heavy hammer to tap around the outer surface of the drum's
circumference. Next, using a short (6"-8") block of wood, position
it at the rear edges the finned drum area and use a heavy hammer to strike
several hardy blows to the other end of the wood block.
(Fig 3) With luck, you will see the drum visibly cock outward on
that side. If it does, rotate the drum 180 degrees and do the same thing
again or continue the rotation process until you get results. This is
the safest and usually quickest way. Working at the rearward edge of the
drum will afford you with the most area to freely swing the hammer. The
wood block is meant to protect the delicate aluminum fins from chipping
off, plus the wood grain end will usually dig in and grip the fins while
protecting the metal
Caution:
Do not continue to beat on just one point on back side of finned drum
without moving to the opposite side (180 degrees) or at least several
inches further along circumference in order to avoid the risk of permanently
warping metal drum from excessive blows concentrated at one point.
Step
2. If you do not break the drum loose quickly with step 1, try
using a heavy rubber mallet (fig. 5) or medium
weight steel mall (read cautions FIRST) to strike modest, tapping blows
to the outer surface of the drum in a circular pattern that works around
the perimeter of the drum just inside the lug nut area (blue
circle shown in Fig. 4a). Next move
to the outer perimeter just inside the finned circle (red
circle shown in Fig. 4a ) and repeat
your modest tapping blows in a circular pattern around the drum
(Fig. 4b).
The aim is to cause the drum to slightly "cock" itself inward
at the point of the blow. By tapping all around the circular perimeter
of the drum, you will be trying to cause the drum to slightly "cock"
inward in all directions, hopefully breaking the bond formed behind the
drum. After 5-10 blows, use your 2 hands to try to rock the drum loose
further and pull it off or return to step 1. If nothing happens, repeat
with more blows and so on.
You can also attempt to work from behind the drum to tap the backside
of the aluminum fins with a small metal hammer, but it is very easy to
do more damage than good and working like this on the car is very cramped.
If you have the entire suspension removed from the car, you can place
a block of hardwood up against the back side of the fins and hammer backwards
on it and reduce the risk of damage quite a bit. Caution. Whack'in too
hard, for too long, at one point, can result in a permanently warped drum.
Big Caution: Getting carried away
with the force of your blows to the outside of the aluminum surface can
result in a permanently warped drum. Go slow and gentle in the beginning.
Heavy metal steel hammers are more likely to do permanent damage compared
to heavy rubber or plastic mallets so choose your tools carefully for
this job. Using a wood block between the metal hammer and drum is also
a good idea.
The
Heat Option. There is a more drastic approach that can be taken,
but not one recommended for the beginner. Some shops will sometimes apply
heat from a propane or welding torch to the outer aluminum drum surface
in an attempt to cause the corrosion and rust bond to be weakened by the
expansion and contraction of the 2 different metal surfaces. Very easy
to permanently damage the drum using this method so use it only as a last
resort.
Approach
Two: A second problem to drum removal results from either brake
shoes becoming frozen in position due to an emergency parking brake being
left tightened for long periods or because brake components and cables
have become gunked up to the point that components will not release with
counter spring pressure . Also, if brake shoes are left in a tightened
position during rainy months, a rust bond will sometimes develop between
the shoe and the drum's steel friction surface (Fig
1b) that can establish a rather strong grip on the shoe.
With the rear of the car jacked up, front wheels braced,transmission out
of gear and the parking brake released, if your brake drum will not rotate
freely or if it drags noticeably, then you may have one of the conditions
mentioned.
Step
1. First, make sure that your parking brake linkage near the backside
of the hub is releasing totally (Fig. 2A).
If the brake cable fastener seems taunt after you release the handle you
may need to tap the connecting lever (Fig. 2B)
with a hammer in the direction of release to remove the tension.
Step
2. Once you are satisfied that the lever has been backed off as
far as is mechanically possible, the next step is to ascertain whether
the brake shoes are backing off far enough to clear any brake drum wear
grooves that they may have sunk into. Sometimes brake shoes wear a groove
so deep into the drum lining that when they disengage from the friction
surface, they still will not retract far enough to allow a drum to be
pulled off without the non-worn, outer edge of the drum from catching
the brake shoe.
If this situation is suspected, there is a manual brake shoe adjustment
access hole (Fig. 4) (usually filled with
a removable rubber plug) on each drum that can be rotated to a point (slightly
off position from dead bottom-see illustration photo in my web site article)
where a small tool, such as a long, thin shank, flat tipped screw driver,
can be used to back off a cogged adjustment wheel inside the drum that
will mechanically retract the brake shoes far enough that they will then
clear the drum friction edge. Hopefully, the drum will then come off without
further problems. Consult a Nissan manual to clarify the fine points of
this adjustment process.
Lastly,
attending to a little preventive maintenance before reinstalling the brake
drum can be wise. Using a wire brush on the end of an electric drill some
80 grit sandpaper, grind down the rust and corrosion areas that caused
the problem in the first place. See Fig. 1A -1B and Fig. 6A and inset
photo that show areas of greatest concern to attend to before reassembly.
Note
of Caution,
I have heard some suggest that an anti seize compound or thick grease
applied to these problem areas before reassembly will protect against
problems in the future, but IMO these products, if applied a wee to aggressively,
can lead to them being spread by centrifugal force out to the brake shoe
area. If these lubricants should get onto friction surfaces, a car's braking
capability could be compromised down the road so use caution with this
approach. Personally, I do not recommend their use in the brake hub areas.
Eric
Neyerlin - owner of Z PARTS
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