This is for a 1.8T but I'm guessing this will be pretty much the same for other engines. Not the most comprehensive write up and lacking pictures but better than the guide I had;)Symptons
My engine would reach 90 degrees but when I went onto a motorway or bypass the temperature would drop of to between 75 and 80 degrees even when the car is up to temperature.Parts Required
Thermostat £16 from VW 050 121 113C
Thermostat O ring £1.98 from VW
Coolant (3 litres in total of VW G12++) £16 from VW (£8 each) GO12A8GM1
. For this you can use stuff from Halfords (or another motor factors) but make sure on the back of the bottle it says it is suitable for your engine. Also you can catch the coolant in a tub and replace that but I replaced mine with fresh as I didn't know how long it had been in there.
Took about 2hr 30 mins to complete from start to finish but this was in snowy conditions so you can probably do it quicker if you're in a garage with warm hands!NOTE: YOU DO NOT NEED TO REMOVE THE ALTERNATOR OR JACK THE VEHICLE UP!
The thermostat is located on the block just to the right (looking into the engine bay) of the alternator.
Remove the engine cover from the top of the engine and also the piece that goes round the inlet manifold. So you're left with this:
Then remove this 'tray' that is in front of the inlet manifold by the two bolts that hold it onto the manifold, also unplug the 2 electrical connections that are connected and underneath there is a bracket holding an air pipe on undo this so you can move this part out of the way of the thermostat. The plastic pipe can also be removed from near the air box so you can get a good view of the thermostat housing. You can also just pull out the dipstick holder out to gain more room.
Now you want to remove the expansion tank cap, and reach to the bottom of the passenger side of the radiator and twist the tap and pull it out to drain the coolant. This should come out for the next few minutes so leave the tap undone.
Now you can remove the pipe that connects to the thermostat, note this will probably still be full of coolant!
Now you can see the two bolts that hold the thermostat housing on:
These can now be removed making sure that the thermostat and O ring come out. They are a bit fiddly to get them out so make sure you don't round the bolts and use a lot of patience.
Should be left with this
You can also use this photo to locate the thermostat in the first place!
You can test the old thermostat in a bowl of hot water (straight from the kettle) mine opened by about 1 or 2mm so wasn't sure at the time whether it was faulty or not. It should also close when you take it out of the water. Although they do take a bit of time.
Right so it's time to refit everything, I greased up the O ring so that it 'stuck' to the thermostat and housing so it was easy to replace back into the whole. I also used some P1600 wet and dry paper to clean up the two surfaces that go together. The thermostat housing and the block. This will create less chance of leaking as it can fit together better.
Obviously re fitting is what I've just said reversed but make sure you:
-Do the tap up on radiator before you replace coolant!
-re-connect the two plugs you disconnected
-re connect the air pipe and fit the dipstick holder back in place.
-re-connect the hose you removed on the thermostat housing.
Now is time to put the coolant in, so make sure the tap is done up on the radiator and pour 3 litres of un-diluted coolant in (at this point it will proboably show full to the maximum. So turn the engine on (make sure all plugs you disconnected are connected and so on!) and give the car a few revs. The water level should drop so top it up again and place the blowers on hot and number 4 in the car aiming at the windscreen. Then hold the car at about 2RPM for a few minutes and rev after. Obviously if the level is dropping keep replacing. when there is warm air coming through shut the engine off and do up the expansion tank cap.
Now fill a few bottle up with water and take the car on a test run, it will probably ask you for more coolant at some point. So just fill with the water and carry on, let the car get up to temperature and see if the needle drops when on a fast road. If it doesn't drop job done! If it does I would look at replacing the temperature sender or even the water pump.
Any problems feel free to PM me or email me and i'll try my best to help you!
The writer of this guide and GolfGTI.co.uk accept no responsibility of damage to your car when using this guide. Use at your own risk.