How do you replace the thermostat located on a 1999 VW Beetle 2.0L?

Answer 1

(pasted from another similar question)Replacing a thermostat is a relatively easy task. If your temperature gauge is running way down on the low side and your heater isn't putting out much heat, it's time to replace the thermostat. Here is a description of how to change a thermostat. The exact location of your thermostat may be slightly different but most of them are near the top radiator hose in the top of the engine.

The thermostat is normally in a housing which is at the engine end of the top radiator hose. Drain the coolant into a drain pan - toss it down the john - it's the correct way to dispose of it. Take a screwdriver and remove the hose clamp from the top hose where it meets the top of the engine. Get a flashlight and see if you can peek down the hole and see the thermostat. If it is faulty it will be open.

Not all thermostat housings are identical but typically it will be held on with two bolts. Remove them. Tap the thermostat housing with a wooden block or a soft faced hammer. It should pop off easily. You can then see the thermostat. Lift it out. Don't sweat the gasket - you are going to replace it anyway. Use a new gasket. Scrape EVERYTHING off both mating surfaces. Use a single edged razor blade. Apply some blue rubber sealant to both sides of the gasket. Then grab it between your fingers and "squeegee" any excess off. You don't need a lot of sealant.

Make sure you put the gasket on the right side of the thermostat. The stat will normally fit into a recess in the engine, the gasket goes on top and the housing on top of that. Wipe a bit of blue rubber sealant inside the hose, put it back onto the housing nipple and clamp it back in place.

You should probably drain all of the coolant by draining the block but if you can't find the small plug it the side of the engine don't sweat it. You should mix antifreeze and water in a ratio of 50-50 and replace what you drained out with the fresh mix. If you can't get all the replacement mix in while it's cold just warm it up a bit and watch the level drop as the thermostat opens up. Then add mix until it is totally filled. Replace the radiator cap and put a quart or so in the overflow bottle (which you should have drained previously).

The above answer could not be more incorrect. First off, the process is not as easy and as straight forward as posted. Lets shoot straight past the authors diagnosis process and get to the meat of this.

Prepare your self with the following tools: 8,10, and 13 millimeter sockets- a large crescent wrench (preferably 8 -10 inches in length)- one medium size rubber mallet, a pair of long and short needle nosed pliers and a single type of pry tool that will fit between the top of the alternator and the mounting bracket.

Facing the engine compartment, your thermostat is located on the left side of the engine block, situated between the thermostat water neck and the block it self. The first thing to do is to disconnect your negative line at the battery, as you will be disconnecting the wiring to the alternator. Next drain the coolant and depending on its age, either replace or recycle it. To drain the fluid is as simple as putting a catch container under the right side of the radiator, directly under the drain nipple that is clearly visible. Next turn the release valve directly above the drain nipple and the coolant will flow.

Now move on to the alternator. Any individual who has ever worked on this vehicle knows for certain that the alternator must be removed because of the limited access to the bottom mounting bolt of the water neck. Begin the alternator process by removing the 13 millimeter nut which secures the source line to the unit. There is just next to the alternator power line another quick disconnect line, and this too must be removed. Simply squeeze the sides of the adapter and the matting face will slide right off. After this, you will need to release the load off the serpentine belt. This single belt design allows for the belt to be removed by attaching one of the fore mentioned crescent wrenches to the tension pulley knob at that top point of the pulley, it stands about and inch high (looks like a rectangle in form). With the mouth of the wrench opened just enough to assure a secure fit to the knob, apply a forward force and the tension will lessen enough to remove the belt from the alternator pulley.

Removing the alternator requires you to take out two bolts that have a 13 mm head, and you will see one at the top of the unit and one at the lower end. The alternator will require some muscling to take out, and this is where your pry tool comes in. Putting the the tool between the alternator and the mounting bracket, and applying a downward force will move the unit from its bolting position. It is in there very snugly! You will be working the unit in a upward and downward direction in order to dislodge from the bottom bot position. That was a pain now wasn't it?!

Three things clearly visible at this point is that A- though tough , due to such a limited access area, removing the alternator was a must B- You can not remove the hose clamp as the previous author outlined. They are not "C" clamp in design and are in fact flex clamps which required a pair of your pliers to remove C- There is not space enough to look at the thermostat to validate its spring position. Even if you suspected the thermostat to be good at this point, for as little as the cost, and with all the effort you have already gone through, REPLACE IT!

Your water neck bots are 10mm, and the top will come our very easily. It is the bottom one that will cause the frustration. Take your time, and you may find it easier, as I did, to loosen it with a nut driver wrench, as the centers are cut for this tool as well. I can almost guarantee you will drop the bottom bolt while either removing it or reattaching it. You will see the small detent it can fall into and your long nose pliers will save the day here.

With the water neck off, you now see the thermostat (it does not require hitting with a hammer as it is plastic and there is not adhesive needing dislodged) remove the thermostat and the rubber "O" ring along with it. Once removed, DO NOT, as advised earlier scrape either of the mating surfaces. Use a little cleaning agent on the water neck and the same of the aluminum block. Are we getting the picture now? A plastic neck and an aluminum block, two of the lightest and most easily damaged materials.

Install the new thermostat. BUY WAIT! Did you notice the rubber "O" rings? They alone are the only seal required for preventing leaks, should you insist on putting an RTV material on either face of the opening, you will for sure then have problems.

Working on our own vehicles requires a lot of patience and time, and I have very little patience for anyone who ill guides one of us in our quests. Should this entry seemed a bit pensive, it was meant to be, be here to help with real value added information, or say nothing at all. Good luck with your project and a happy new year to you and yours.