Shared Knowledge
"BMW Z3 - How to Replace the AC and Serpentine Belt"
16 February 2013
Summary: easy do it yourself (DIY) with either just your hands or some sort of pry bar.
Background:
BMW Z3: 1997, 55,000 miles.
No specific problem with belts but going to change radiator hoses, etc, so decided to change belts.
Note: belts should be visually checked ever so often (annually) for signs of cracking. These belts do have a finite life and should be replaced as a preventive measure. If the serpentine belt goes out on you when you are out and about, you are stuck as no water pump, alternator and power steering, plus any damage the ripped belt might do to surrounding components.
Note: I did not replace tensioners but certainly could have and eventually not a bad idea.
On the 1997, BMW used the old style tensioners that are not adjustable.
Tools needed:
32millimeter (mm) thin wrench.
10 and 11mm socket and ratchet.
Perhaps a 5 foot pry bar of some type.
New AC and serpentine belts for you exact model Z3. Available from BMW or multiple other sources on the Internet.
How to remove the AC and serpentine belt:
Remove the water pump fan. To do this you need a thin 32MM wrench that can be had from a bicycle store.
Place thin wrench on fan nut and as fan is thread opposite of normal, you turn wrench to the right to loosen nut.
May have to use a long, thin, flat blade screwdriver between 2 of the fan pulley bolts to keep the water pump from turning.
Once fan is loose, use you hands to completely unthread the fan and keep it from dropping.
Place fan leaning against the radiator for now.
Remove the 2 bolts holding the air filter box to the chassis, unclip the air box from the mass air flow (MAF) sensor, pull the box up and out.
Now take water pump fan out of the fan shroud by working it slowly towards the opening you created when you removed the air box.
Set park brake: tight, well.
Jack up Z3 on passenger side front.
Crawl under car and locate the AC belt on the passenger side of car. Pull down on the belt where you can place your hand and see how the belt tensioner works.
In my case, I was able to pull the belt with my hands enough to be able to slip the belt off the AC pulley. If you have difficulty doing this, you might have to use some sort of pry bar.
With belt off AC pulley, remove from crank shaft pulley and remove from car.
Move around to front of car near where you removed the air box.
Looking down, you will see the serpentine belt. Again place you hands on the belt and pull to see how the tensioner works.
In my case, I was able to pull the belt by hand enough to get it to slip off the alternator pulley.
If you have difficulty pulling the belt off, you might have to use a pry bar of some type to release tension of the belt tensioner.
With the serpentine belt loose, remove it completely from car.
How to install new belts:
Take you new serpentine belt, unfold it and using the diagram below, thread it around all pulleys to include the tensioner but not the alternator. The serpentine belt goes on the first threads of the crankshaft pulley. Note that diagram is view from standing in front of car looking down.
Note, the tensioner always has the flat side of the belt wrapped around it.
With the serpentine belt in place, use your hands to pull up and back on the belt and get it to slip over the alternator pulley.
Again, if you have difficulty doing this, use a pry bar on the tension roller.
With the serpentine belt in place, confirm it is on the inner grooves of the crank shaft pulley and complete around all other pulleys and the belt tensioner.
Crawl under car and place AC belt around crankshaft pulley and belt tensioner.
Again, pull the belt until you can slip it around and on the AC pulley.
A pry bar on the tensioner roller maybe required if you can not do by hand.
After belts are on:
After you have both belts on all pulleys, check your work.
Belts fully on all pulley's?
Belts mounted correctly according to diagrams above??
All tools out, away from car??
Start the car and check running belts. As no water pump fan in place, do not run car for more than couple minutes.
Shut down car.
Lower car off jack.
Take water pump fan and move it back into fan shroud.
Move fan up to water pump shaft and thread fan back onto water pump shaft. In this case, you going to turn the fan nut to the left to get fan to tighten.
Once fan is properly on water pump shaft, use the 32mm thin wrench to tighten. You may have to use a long, thin flat blade screw driver wedged between 2 fan pulley bolts to get leverage to turn the fan nut tight.
Take air box and move back into car. Box goes in at an angle and then down and once in place, clip MAF back in place and bolt box to chassis.
With all done, check your work again.
No tools anywhere around car?
Start car and look at instrument panel and check all lights are as they should be.
All done.
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