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Old 01-11-2010, 12:43 PM
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Default MK4 1.8T Thermostat Replace

So after replacing my coolant temp sensor I discovered the car was running really cold (It has been extremely chilly here in central FL if the news hasn't told you). the car pretty much only hits 190 degrees when its idling and thats after a while.

I'm ALMOST certain its the thermostat stuck open. I have replaced them before and never had as hard of a time as I am having now. I have tried getting to the bottom bolt on the thermostat housing, but it seems like you would have to remove the a/c compressor to remove that bolt. Its incredibly cramped to work in and I don't see how else this job could be done. I have found a few write ups on passat's, but the thermostat location/bolt positions are very different. You cant even see the bottom bolt on this one.

I was going to buy a wobble extension set but I really don't think that will work.

Are there any write ups with pics on replacing it? I think I am ready for a timing belt too and judging by the effort I might just have a shop do both things at once.

Thanks
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Old 01-11-2010, 01:40 PM
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I will post a write up for you in like 15 minutes...I am running outside as I have customers here to buy a car. Once they leave, I will come back inside, and help you out
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VW and Audi are a lot like a really hot girlfriend...looks great, amazing in bed, but every once in awhile you gotta throw some money down on the table so she sticks around.
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Old 01-11-2010, 01:43 PM
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here's a quick write up..I have another 5 minutes before they show

Just drain the coolant, pull the hose off the Thermostat Housing, remove the bolts holding the housing to the engine
, thermostat comes right out. Pay attention which way the Thermostat is pointing. There is a little pin on one side of it. You want to install the new Thermostat in pointing in the same direction.
I hope this helps you.
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Originally Posted by TTTurbo1.8T View Post
VW and Audi are a lot like a really hot girlfriend...looks great, amazing in bed, but every once in awhile you gotta throw some money down on the table so she sticks around.
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Old 01-11-2010, 03:22 PM
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Use a 1/4" drive with wobble (u-joint) and correct socket. I did it on my 2.0L without much trouble, did not need to move compressor.
The trick is getting that bolt back in. Some thick grease in the socket or aluminum foil will help hold the bolt in the socket as you sneak it back in.
Patience.
It can be done.
Good luck and make sure the new o-ring seats the first time. Don't ask...
Dan
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Old 01-11-2010, 10:02 PM
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Hey thanks guys,

I was able to get the thermostat changed. I knew where it was, and how to replace it, I just didn't know how to get to the bottom bolt. A 2.0 engine and a 1.8 passat engine have different designs from a mk4 1.8 from what i understand. Although they are similar, my thermostat housing as well as the spaces were not the same as them. My plastic thermostat housing has a bolt the top and bottom of the housing, unlike the passat, which apparently has them on the left and right side. It also does not have the space clearance that I saw was present in the 2.0

We ended up getting the bottom bolt off through the use of a hell of a lot of 1/4 extensions, a flexible socket (with some electrical tape around it to keep it firmly pointed in the direction it needed to go), and an Allen head. Luckily the bolts have an Allen head in the middle. Without this there was no conceivable way we could put a 10mm socket at that angle on there.

Also, a little trick i learned for the bottom bolt is to place it into the thermostat housing before you screw it back in, and secure it in place by tying thin fishing line on threads. this will keep it from falling out of place when you are trying to screw it back in.

Because of my large ape hands, it helped me to remove the radiator fan on the side of the thermostat, along with the black metal braked connected to the manifold. I also zip tied all of the tubes out of the way.


P.S. If anyone wants a "specialty mk4 1.8 thermostat wrench" you can find them in my store on ebay for 89.99. Electrical tape not included.
Attached Thumbnails
MK4 1.8T Thermostat Replace-011110145742_01.jpg   MK4 1.8T Thermostat Replace-011110160824_01.jpg  

Last edited by KSJNX; 01-11-2010 at 10:09 PM.
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Old 02-01-2011, 06:55 PM
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I managed to do this removing the dipstick support bracket and, critically, the wire clamp on the side of the alternator which allowed a better angle in to the bottom bolt. Fiddly if you have big hands but doable with patience !
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