This DIY is contributed by Tom Trawinski
Updates made by Robin on June,2000 including pictures.
Difficulty scale (10 being hardest): 6
Adjustable wrench (or 24mm or 15/16" open end wrench)
Complete belts listing:
(from Porsche parts catalog)
(1) Start with the
A/C belt. Loosen A/C bracket with 4mm allen key. For 96+ 993s
the A/C bracket uses a 8mm bolt. And make sure the lines can move
back & forth freely.
(2) On the right
side of A/C compressor prior to loosen the adjuster locking bolt with 13mm
wrench use a 13mm wrench turn the tension adjustment bolt a couple of turns
first and thenloosen adjustment bolt lock nut with the wrench.
Proceed to loosen the tension adjustment bolt few more turns.
(3) Using 13mm socket
with extension to loosen the two bolts under the A/C lines (one is short,
one is very long). Remove the other three bolts that hold down the
compressor. Be careful not to lose the square nuts, put yours hand
underneath the square buts to prevent them from falling. Lift the
compressor off its base just few cm toward to the center of the car once
all the mounting bolts have been removed. Lift the belt from the
pulley first, then pull it off the crank pulley.
(4) Using the Porsche
special tool# 999 571 052 02 and a 24mm wrench to loosen the alternator
shaft bolt. The special tool holds the shaft in place to prevent
it from spinning while you break the nut free.
(5) Remove the three
bolts with a 5mm hex bit and ratchet. Do not use allen keys as the
heads can strip very easily. Spray a little penetrant on bolts to
help loosen them up. A trick to do to prevent the 5 mm allen
nuts from stripping is to break the nut loose by hitting the ratchet handle
with a hard jolt. After removing them make note of how many shims
are on the outside of the pulley and the little white tab (the white tabs
only exists on 95 993s). The outer pulley half and shims have
a small index hole that the white tab fits through. You will
need to line it all up when installing. Pull the outer pulley half
off. To get the belt off slide the wheel sensor to the left.
(6) Get ready to install the new belts.
(7) Install fan belt on to crank pulley and center top part over alternator shaft. (If the belt do not fit easily into the crank pulley, use an long object like a long 3/8" extension to push the belt into the crank pulley.) Be sure to lift up the fan belt follower to avoid breaking it. Line up white tab with holes and slide outer fan pulley & shims on to the alternator shaft as far as it will go. Thread all three bolts by hand. To tighten the pulley squeeze the belt at the midpoint between the crank & fan pulleys. Tighten each bolt a little, and repeat a few times until bolts are tight w/o crunching the belt. You can line it up by pulling the belt either way a few times. Do not force the bolts tight. Use finesse. When the bolts are tightened up crank the starter two or three times to get the belt to sit correctly (try not to start the engine). Check the tension of the belt. If it is too loose or too tight, add shims (to loosen) or remove shims (to tighten).
(9) Slide one half of the pulley with the smooth side facing out. Place alternator belt over crank pulley and center it over shaft. Slide other pulley half on with smooth side facing in as far as possible and thread the 24mm nut (15/16" nut) by hand. Use the adjustable wrench & torx bit until tight. Follow the same procedure to tighten this as the fan belt pulley. Remember a little finesse is needed here. After it is tight start engine. Make sure the fan & alternator dashboard light go out, and then check that the belts are turning smoothly. Shut off engine and check the belts tension. They should deflect about ¼ inch.
(10) Install the A/C belt over crank pulley, then over the compressor. Slide compressor to right and start tightening the adjustment bolt. Do not tighten all the way yet. Insert the three long mounting bolts in their holes. They should slide all the way down. If they donít then tighten up adjuster bolt until they are completely inserted. Place square nuts on each end and tighten up. Check belt tension, it should feel tight and deflect about ¼ inch at most. Adjust it by loosening up the three long bolts and turn the adjustment bolt until desired belt tension is set. Tighten all the long bolts, the short bolt, then lock the adjustment bolt in place (hint: loosen it up slightly, tighten inner nut by hand, and tighten bolt). Tighten the A/C lines bracket.
the engine and turn on the A/C. All belts should turn freely &
smoothly. Place old belts in your trunk as spares. Take the
car out for a test drive. When you get back inspect belts to make
sure all is OK.
Belt tension tips from Skip
Porsche part number 000 721 957 40 (and about $40 as I recall) gets you special tool number 9574, the Gates "Krikit" V-Belt Tension Gage (which is probably $10 at an AutoZone near you). Of course, your $500 Porsche factory manual set provides 3 full pages of instructions for using the thing, whereas you only get 1/2 of a Xeroxed page printed in 1981 with it - so I guess we shouldn't complain too much. It's a rudimentary gage about 4" long that measures in both foot/lbs and kgs. Porsche gives their specs in "increments" of the kg scale. Per the manuals, these are the belt specs for both the 993 and the 993 TT: Alternator and fan belts: When fitting new belt: 23-35 increments cold, 28-40 once run for 15 mins/10 miles Checking used belt: 15-23 increments cold, 20-28 at op temp. Adjustment not needed unless below 15/20. A/c belt : 30-35 increments at op temp
Hope this helps Skip
Addition belt change or tension documents by Bill Noble
When I took my belts off the 2nd time to check for squeaking noise I accidentally stripped the alternator shaft since I was using the incorrect tool to hold the shaft still. If you are interested to see how I fixed the stripped alternator shaft