There is a post on here written by "JDriver1.8T", (Alternator DIY-1.8T). His post was very helpful in getting me to change my wife's thermostat that the VW dealership wanted 700$ for!
I made this post for guys like me who are a far cry from being a gear head. I am no mechanic, so bear that in mind for this thread.
I am using some of JDriver1.8T's photos, I hope he doesn't mind. Rather than making two threads, one for the alternator, and one for thermostat, I am going to save myself some time, and just make one.
Time--- It took me the better part of 4 hours---, with good directions, I think you could beat that.
Step # 1-- Remove all the plastic covers shown below. To remove the battery cover, there are two indent tabs on the R and L side. Push them in and the cover will slide off. The srews on the other covers are 1/4 turn and release.
Step #2-- DC the battery red side (Positive)
Step #2.1--- You may find it easier to get at the wires on the back of the alternator and most definately easier to access the thermostat if you unscrew this manifold that is attached to the yellow oil dipstick tube (Sorry the picture below doesn't show it real well). This manifold is easily detached by unscrewing the 2 allen heads holding it in place. You do not need to disconnect any of the wires or hoses attached to it. You are just detaching it so you can tie it off out of your way. USE CAUTION when removing this manifold--- it has a tab recessed into the yellow oil dipstick tube--- that tube can become very brittle and will break VERY easily, like I found out the hard way (I had to replace it--15$ fix). Just be very gentle around that tube and when sliding the manifold tab out of it.
Step #3--- Locate the alternator and the thermostat. The alternator should be easy enough to spot. The thermostat is behind the alternator where the arrow below is pointing. Just follow the radiator hose to the block and you can see the housing for it. If you are changing the thermostat, don't panic, I know it looks like you need to lift the engine out to get to it.
Step # 4--- You may want to move or disconnect the wiring to the back of your R headlight just to get it out of the way
Step #5--- Disconnect the throttle body hose (clamp with red arrow pointing to it, picture below) and throttle body (I think that's what they are) as shown in the photo below. You do not need to disconnect anything that is attached to the the throttle body, just undo the four 5mm allen (hex) head bolts. There is a gasket on the throttle body---don't lose it. You can then use bungies or tie downs to hold it out of your way.
Step #6-- Locate the tensioner for the serpintine belt shown below. This is where my directions differ from JDriver1.8T's---He recommends removing the tensioner, I didn't. It should be easier to see with the throttle body out of the way. The red arrow is pointing at the tab. You use a wrench to rotate that tab to the right. It is spring loaded and will take a little umph to get it to move to the right. Get down there and take a good look at it. You will notice a hole right where the red arrow is pointing, and you will notice another hole on the housing where the green arrow is pointing. Your goal is to rotate it far enough to get those holes to line up, and then shove a nail or similar object through both holes to lock the tensioner in a released position.
Step #7--- Remove the two bolts holding the alternator in. With the throttle body out of the way, you should be able to access both of these bolts. I wont lie, it aint gonna be easy. A knuckle joint is needed on your ratchet. The picture below shows the top bolt. The bottom bolt is down lower. You do not need to remove the two bolts holding the tensioner in place.
Step #8---Unwind the serpintine belt from around the alternator, it should be fairly easy with the tensioner released.
Step #9--- Get a crow bar and pry alternator out---that is the only way it will come out. With the throttle body out of the way, you should be able to slide the crow bar down behind the alternator and between the block.
Step #10--- DC the wires on the alternator.
Step #11--- remove the alternator--- I was able to wrestle it out by twisting it and turning it and holding other stuff out of my way---kinda like a chinese jigsaw puzzle, which I am terrible at.
Step #12--- With all this done, you should be able to access the thermostat housing. You might feel like you can remove it without taking the alternator competely out--- Word to the wise, take it out, because there is a later step to get the alternator back in that will be much easier to do with it out. KEEP IN MIND when you remove the thermostat housing, coolant will begin leaking out. Have a basin (large one) underneath the car if you haven't drainied it off pryor. There are two bolts holding the housing in place. Take them off--- I left the hose attached and then just tied the hose and housing out of my way. Remove the old thermostat and the gasket, paying attention to the direction--- DO NOT REVERSE IT when putting the new one in.
If you made it this far----GOOD JOB--- If you made it this far and didn't break your oil dipstick tube, or leak coolant on your driveway--- BETTER JOB.
Step #13--- Put in new thermostat--- you should be able to push it in there, and have it stay. Thermostat first, then the gasket--- push it in place and it should stay. When tightening the housing bolts, do it evenly---don't crank one side down hard while the other is still lose.
Step #14---Reverse the process for reinstalling the alternator---- SPECIAL INSTRUCTIONS FOR ALTERNATOR. When you remove the alternator, the threaded part is a pressed in bushing that will be MUCH too tight for you to get the alternator back on. To fix this, with your alternator still out where you can work on it, thread your bolt back through the alternator, almost all the way in, but leave about an 1/8th inch gap. Take a hammer and pound on the head part. Your goal is to get that bushing to slide out enough to give you space to get it back on. Refer to picture below.
Step # 15--- Once the alternator is back in and TIGHT--- make dang sure you tightened it enough to get those threaded bushings to slide back up to TIGHT. Next you need to make sure you route the serpintine belt correctly. See diagram below. You need to get in there with a light and make certain it is routed right and SEATED on the trac properly, everywhere. You can actually reach that bottom pulley from underneath the car to make certain the belt is correct there.
Step #16--- Release the tensioner and then double check that the belt is alligned properly.
Don't forget to refill your coolant.
My thanks again to JDriver1.8T, I just fine tuned your post a lil.
I hope it was helpful for you DIYers. There is nothing I hate more than paying ridiculous sums to the dealer.