Replacing the 3 or 4 belts on a 900 is something we all have to do numerous times during our ownership of these cars. I like to change belts on mine every 3 years, and today I did this for the first time as a job in itself rather than as part of a more involved repair.
As I do whenever I can, I tried to find the simplest and quickest way to do this job. I managed it in less than an hour, which included the standing-around-and-thinking time; plus, the car is a 1990 900S with both AC and ABS--so there's as much extra junk in the way as you could ever expect on these cars
Here goes:
(1) If you do not have an AC compressor, skip this step and go to step 2. If you do have one, begin by cutting any cable ties that hold the main wiring harness to the AC hoses. Lift the harness up and over onto the cam cover until it's near the PCV valve, and is now out of your way.
All nuts & bolts in this step are 13 mm.
Then, slacken the 2 bolts attaching the AC tensioner pulley mount (a thick triangular steel plate) to the head. Use a long box wrench (ring spanner, in English:cheesy: ).
Using a deep-wall socket (or an offset ratchet wrench, or plain wrench) on the adjuster nut, back it off until there's no more tension in the belt (you won't be able to remove the belt yet, though).
Now, remove the upper of the 2 mounting bolts and its washer, and pivot the tensioner down; remove the belt.
Remove the lower bolt, and lift out the tensioner. Look the triangular plate over for cracks, and spin the pulley to see if its bearing is smooth and quiet. (If you find problems, the pulley is about $15 and www.eeuroparts.com sells the entire tensioner assembly for something like $70.) Back off the adjuster nut until it's about 1/4" (1/2 cm) from the end of its threaded rod (use vise-grips to clamp the rod's other end onto the triangular plate, or put the whole thing in a vise).
(2) Slacken the bolt and nut holding the power steering pump to the head and to the RH engine mount, respectively. Slacken the adjuster nut (yes, another threaded-rod type thing) by about 1/2" (1 cm). You can use a normal wrench for this, but it takes forever--so I made a special tool by taking a cheapo 13 mm open-jaw wrench and bending it to a 45-degree angle just below the jaws (cut it to length if it's too hard to maneuver). Loosen the mounting nut until it's almost off (but not completely off:nono;, or you'll lose the bolt it screws onto--this bolt was designed to fall out when the nut is removed). Pull the nut end of the threaded rod towards the firewall to get it of the adjuster fork. Push the pump towards the engine centerline and pull its belt off (you may need to pry with a screwdriver to get it out of the pump pulley completely).
(3) Slacken the 16 mm nut on top of the alternator. Back off the alt. adjuster's 10 mm nut about 1/2" (1 cm)--a ratcheting wrench helps here. (This is the last threaded rod--I promise.) Completely remove the 16 mm nut, and pull the adjuster towards the firewall until it's out of the alt.
Now for the clever part: Cut yourself a wedge from a piece of wood (2 x 4 is perfect), with a rise of 3" (8 cm) and a run of about 12" (30 cm). Push the alt. towards the engine, and shove the wedge in between the side of the alt. and the coil-spring tower (master cylinder mounting bracket works, too). Keep pushing the alt. and driving the wedge down until the alt. is so close to the engine that it's compressing the lower heater hose.
Pull the outer belt off the alt. pulley. Working from the RH side of the car, lift the belt off the water pump pulley and then disengage it from the crank pulley. Now, pull the inner belt into the outer groove of the water pump pulley. Go back to the LH side of the car, and move the inner belt into the alt. pulley's outer groove. Try removing it from this pulley; if too difficult, either wedge the alt. closer to the engine or try pulling the belt off the water pump pulley from the RH side of the car (a helper is very useful for all this).
(4) Install the new inner belt by fitting it into its groove in the crank pulley first. Work it into the outer grooves of the alt. and water pump pulleys, then into the inner ones. Install the outer belt--again, first onto the crank pulley, then the water pump and alt. pulleys.
Remove wedge. Insert tensioner into alt. making sure the threaded rod settles into its fork, and refit its 16 mm nut--but don't fully tighten it yet. Tighten 10 mm adjuster nut until belts can be pushed in only 1/2" (1 cm) by thumb pressure (applied 1/2 way between water pump and crank pulleys).
(5) Push PS pump as close to engine centerline as possible, and finger-tighten its mounting bolt to hold it there. Fit a new belt around the crank pulley first, then work it into the pump pulley groove from the bottom of the pulley until it pops in. You may need to use both hands, and/or carefully pry the belt on with a screwdriver.
Loosen the bolt you just tightened. Pull the pump away from engine centerline, insert threaded rod into its fork (you may have to back the adjuster nut off some more), tighten the mounting nut (but not completely), and screw in the adjuster nut until the belt deflects as described in (4) above.
(6) Start the engine. Blip throttle, watching the belts deflect as the engine speed goes up and down. If the "blur" you see midway down each belt is over 1" (2 cm) wide, tighten the belt(s) until it isn't. Tighten the PS pump mounting nut and bolt, and the 16mm nut on the alt.
If your car doesn't have AC, your belt replacement is over!
(7) If you have AC, reattach the tensioner to the head with the lower bolt only (and leave this bolt finger-tight). Fit the new belt around the crank pulley, then around the compressor pulley and, finally, around the tensioner.
Reinstall the top tensioner bolt and its washer. Be careful and patient here--you're threading a steel bolt into aluminum, so make sure it goes in straight. You may have to back off the tensioner nut a little. Leave this bolt finger-tight.
Screw in the adjuster nut to get the deflection as described in (4) above. Start the engine, and blip throttle. Watch belt's "blur" on LH side of engine. Adjust as in (6). Switch on compressor, and repeat.
If satisfied, tighten the 2 tensioner bolts. Return wiring harness to its original position, and re-secure with cable ties if needed. Done!
As I do whenever I can, I tried to find the simplest and quickest way to do this job. I managed it in less than an hour, which included the standing-around-and-thinking time; plus, the car is a 1990 900S with both AC and ABS--so there's as much extra junk in the way as you could ever expect on these cars
Here goes:
(1) If you do not have an AC compressor, skip this step and go to step 2. If you do have one, begin by cutting any cable ties that hold the main wiring harness to the AC hoses. Lift the harness up and over onto the cam cover until it's near the PCV valve, and is now out of your way.
All nuts & bolts in this step are 13 mm.
Then, slacken the 2 bolts attaching the AC tensioner pulley mount (a thick triangular steel plate) to the head. Use a long box wrench (ring spanner, in English:cheesy: ).
Using a deep-wall socket (or an offset ratchet wrench, or plain wrench) on the adjuster nut, back it off until there's no more tension in the belt (you won't be able to remove the belt yet, though).
Now, remove the upper of the 2 mounting bolts and its washer, and pivot the tensioner down; remove the belt.
Remove the lower bolt, and lift out the tensioner. Look the triangular plate over for cracks, and spin the pulley to see if its bearing is smooth and quiet. (If you find problems, the pulley is about $15 and www.eeuroparts.com sells the entire tensioner assembly for something like $70.) Back off the adjuster nut until it's about 1/4" (1/2 cm) from the end of its threaded rod (use vise-grips to clamp the rod's other end onto the triangular plate, or put the whole thing in a vise).
(2) Slacken the bolt and nut holding the power steering pump to the head and to the RH engine mount, respectively. Slacken the adjuster nut (yes, another threaded-rod type thing) by about 1/2" (1 cm). You can use a normal wrench for this, but it takes forever--so I made a special tool by taking a cheapo 13 mm open-jaw wrench and bending it to a 45-degree angle just below the jaws (cut it to length if it's too hard to maneuver). Loosen the mounting nut until it's almost off (but not completely off:nono;, or you'll lose the bolt it screws onto--this bolt was designed to fall out when the nut is removed). Pull the nut end of the threaded rod towards the firewall to get it of the adjuster fork. Push the pump towards the engine centerline and pull its belt off (you may need to pry with a screwdriver to get it out of the pump pulley completely).
(3) Slacken the 16 mm nut on top of the alternator. Back off the alt. adjuster's 10 mm nut about 1/2" (1 cm)--a ratcheting wrench helps here. (This is the last threaded rod--I promise.) Completely remove the 16 mm nut, and pull the adjuster towards the firewall until it's out of the alt.
Now for the clever part: Cut yourself a wedge from a piece of wood (2 x 4 is perfect), with a rise of 3" (8 cm) and a run of about 12" (30 cm). Push the alt. towards the engine, and shove the wedge in between the side of the alt. and the coil-spring tower (master cylinder mounting bracket works, too). Keep pushing the alt. and driving the wedge down until the alt. is so close to the engine that it's compressing the lower heater hose.
Pull the outer belt off the alt. pulley. Working from the RH side of the car, lift the belt off the water pump pulley and then disengage it from the crank pulley. Now, pull the inner belt into the outer groove of the water pump pulley. Go back to the LH side of the car, and move the inner belt into the alt. pulley's outer groove. Try removing it from this pulley; if too difficult, either wedge the alt. closer to the engine or try pulling the belt off the water pump pulley from the RH side of the car (a helper is very useful for all this).
(4) Install the new inner belt by fitting it into its groove in the crank pulley first. Work it into the outer grooves of the alt. and water pump pulleys, then into the inner ones. Install the outer belt--again, first onto the crank pulley, then the water pump and alt. pulleys.
Remove wedge. Insert tensioner into alt. making sure the threaded rod settles into its fork, and refit its 16 mm nut--but don't fully tighten it yet. Tighten 10 mm adjuster nut until belts can be pushed in only 1/2" (1 cm) by thumb pressure (applied 1/2 way between water pump and crank pulleys).
(5) Push PS pump as close to engine centerline as possible, and finger-tighten its mounting bolt to hold it there. Fit a new belt around the crank pulley first, then work it into the pump pulley groove from the bottom of the pulley until it pops in. You may need to use both hands, and/or carefully pry the belt on with a screwdriver.
Loosen the bolt you just tightened. Pull the pump away from engine centerline, insert threaded rod into its fork (you may have to back the adjuster nut off some more), tighten the mounting nut (but not completely), and screw in the adjuster nut until the belt deflects as described in (4) above.
(6) Start the engine. Blip throttle, watching the belts deflect as the engine speed goes up and down. If the "blur" you see midway down each belt is over 1" (2 cm) wide, tighten the belt(s) until it isn't. Tighten the PS pump mounting nut and bolt, and the 16mm nut on the alt.
If your car doesn't have AC, your belt replacement is over!
(7) If you have AC, reattach the tensioner to the head with the lower bolt only (and leave this bolt finger-tight). Fit the new belt around the crank pulley, then around the compressor pulley and, finally, around the tensioner.
Reinstall the top tensioner bolt and its washer. Be careful and patient here--you're threading a steel bolt into aluminum, so make sure it goes in straight. You may have to back off the tensioner nut a little. Leave this bolt finger-tight.
Screw in the adjuster nut to get the deflection as described in (4) above. Start the engine, and blip throttle. Watch belt's "blur" on LH side of engine. Adjust as in (6). Switch on compressor, and repeat.
If satisfied, tighten the 2 tensioner bolts. Return wiring harness to its original position, and re-secure with cable ties if needed. Done!
