thermostat

I know that the thermostat is at the bottom of the engine and somewhere inside of the water pump housing. Could someone please tell me exactly how to do this? How much anti-freeze will I need to fill it back up again? And do I just put it in the reserve tank and fill it like that?

Follow the lower radiator hose to an aluminum or plastic part bolted to the water pump. This part is sometimes called the "gooseneck". Removing the hose from the gooseneck will let a lot of coolant out of the radiator so be prepared with a drain pan. Carefully remove the screws holding the gooseneck onto the water pump and the T-stat will be inside. Be prepared for more coolant to come out. If the screws are not moving easily don't force them or you'll snap them off and create a lot more work for yourself or whoever you hire to fix it. Use heat (from a propane torch, for example) to heat the housing where the threads are until the screws loosen. Be patient. And be careful you don't set your car alight! Once the gooseneck is off, you'll see the T-stat inside and note the orientation because it is directional. Use the correct temperature replacement T-stat as specified by VW. Don't go cooler because the engine will never get up to proper operating temperature and the engine computer will think the car is still "warming up" and richen the mixture which causes fuel economy and performance to decrease. Don't believe the boneheads who say a cooler T-stat increases performance because it doesn't! VW (and other automakers) has spent millions designing and testing their engines to get the most economy and power out of them. If they say use a 195 degree T-stat, then that is what you will use. An engine run for an extended period of time with a cooler T-stat can develop carbon deposits on the intake valves and pistons both of which decrease performance. Carbon on the intake valves can impede the flow of air into the cylinders and cause longer warm-up times and carbon the the top of the pistons can increase the compression ratio causing the engine to ping which the engine computer tries to fix by retarding timing which hurts performance. Getting back to the T-stat R&R (remove and replace), if your coolant was very rusty you may want to flush the block and radiator by squirting a hose in the T-stat hole (T-stat removed) and into the lower rad. hose until it comes out fairly clear. Once that is done, reinstall everything and fill the expansion tank ("reserve tank") with antifreeze (coolant)--you'll need at least a gallon. Use straight antifreeze if you flushed the system because there will only be water in it. Otherwise use 50/50 or what the antifreeze maker suggests for your climate. The system will self-bleed over time but you can speed up the process by removing one of the heater hoses from the firewall and reconnecting once the coolant (antifreeze) starts coming out. Run the car at an idle and check for leaks and top off the "reserve tank" as necessary. Keep an eye on the temp. gauge just in case. Once the cooling fan comes on you are done. Hope this info helps!