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Pelican Technical Article:

Replacing Your Thermostat

Steve Vernon

Time:

2 hours2 hrs

Tab:

$10 to $40

Talent:

**

Tools:

T30 Torx, 5mm Triple square, 10mm socket and extensions, pliers, flathead screwdriver, large bucket

Applicable Models:

VW GTI (2006-09)

Parts Required:

Thermostat, gasket

Hot Tip:

Work on a cold engine

Performance Gain:

Engine runs at the proper temperature
Begin by safely jacking up and supporting your car.
Figure 1

Begin by safely jacking up and supporting your car. With the car safely off the ground you will need to remove the engine tray (red arrow) and the right and left side lower wheel well panel (yellow arrow). A great many of these car have had the engine trays and front side panels removed over the years and not replaced. If you happen to have a car that still has all the under trays and original hardware please see our article on under tray removal

There is no drain plug on the radiator in the GTI MkV.
Figure 2

There is no drain plug on the radiator in the GTI MkV. You will need to remove the lower radiator on the right hand side. Place a large bucket or catch tray under the right side of the radiator. This hose is a quick release connection and you should be able to insert a screwdriver and unclip the connection (red arrow) and separate the hose from the radiator.

Our quick release connection was stuck, so we had to remove the standard hose clamp (red arrow) and remove the hose that way.
Figure 3

Our quick release connection was stuck, so we had to remove the standard hose clamp (red arrow) and remove the hose that way.

With the hose disconnected the coolant will drain out of both the radiator (red arrow) and the hose.
Figure 4

With the hose disconnected the coolant will drain out of both the radiator (red arrow) and the hose. The Turbo hose is directly in the way of the draining coolant (yellow arrow) so I used the two quick disconnects and removed the turbo hose. You might want to do this as it really helps avoid a mess.

Disconnect the ground strap from the battery terminal (red arrow) and place the cable (yellow arrow) where it can not accidentally come in contact with the battery while working.
Figure 5

Disconnect the ground strap from the battery terminal (red arrow) and place the cable (yellow arrow) where it can not accidentally come in contact with the battery while working. For more information please see our article on battery replacement.

Remove the ribbed drive belt and lock the tensioner in the locked position.
Figure 6

Remove the ribbed drive belt and lock the tensioner in the locked position. Begin by marking the direction of the belt (red arrow), place a 17mm wrench (yellow arrow) on the nub on the tensioner and turn it clockwise, then insert a 3mm Allen to lock (green arrow) in position. Please see our article on replacing your ribbed drive belt for additional assistance.

You will need to remove the alternator to gain access to the thermostat.
Figure 7

You will need to remove the alternator to gain access to the thermostat. Please see our article on alternator removal for additional assistance.

On the lower left side unclip the quick release clip from the lower turbo hose and separate the hose from the intercooler (red arrow).
Figure 8

On the lower left side unclip the quick release clip from the lower turbo hose and separate the hose from the intercooler (red arrow).

Disconnect the wiring connection (red arrow) from the boost sensor (yellow arrow) on the charged air intake pipe.
Figure 9

Disconnect the wiring connection (red arrow) from the boost sensor (yellow arrow) on the charged air intake pipe.

This photo illustrates the side of the motor that faces the radiator.
Figure 10

This photo illustrates the side of the motor that faces the radiator. This photo is for demonstration purposes only; you do NOT need to remove the front of the car to replace the thermostat. With the front removed you can see the components you will be working on. The thermostat (red arrow) is hidden behind the throttle body intake tube, the lower radiator hose (blue arrow), the charged air intake tube (yellow arrow), the additional coolant hoses (purple arrow) and the intake hose (green arrow).

This photo illustrates the thermostat that is included in the thermostat housing (red arrow) along with the two coolant hoses (green arrows) and the lower radiator hose quick release connection (yellow arrow).
Figure 11

This photo illustrates the thermostat that is included in the thermostat housing (red arrow) along with the two coolant hoses (green arrows) and the lower radiator hose quick release connection (yellow arrow).

Use a flathead screwdriver and loosen the clamp on the throttle body hose (red arrow).
Figure 12

Use a flathead screwdriver and loosen the clamp on the throttle body hose (red arrow).

Working from below remove the T30 screw holding the charged air pipe bracket to the engine (red arrow).
Figure 13

Working from below remove the T30 screw holding the charged air pipe bracket to the engine (red arrow).

Working from the top of the vehicle remove the 10mm nut (red arrow) holding the charged air pipe bracket on and remove the pipe.
Figure 14

Working from the top of the vehicle remove the 10mm nut (red arrow) holding the charged air pipe bracket on and remove the pipe. Use care to wiggle it and the intake hose off the throttle body and out through the bottom of the vehicle.

Remove the hose clamp and hose from the top outlet on the thermostat (red arrow).
Figure 15

Remove the hose clamp and hose from the top outlet on the thermostat (red arrow).

Disconnect the quick release coupling on the lower radiator hose (red arrow) and separate the hose from the thermostat housing.
Figure 16

Disconnect the quick release coupling on the lower radiator hose (red arrow) and separate the hose from the thermostat housing. Note; our coupling would not separate no matter what we tried so we had to remove it along with the thermostat from the engine. There is a clamp on the lower hose you need to release.

Use a T30 Torx and remove the screw holding the pipe in the housing (red arrow).
Figure 17

Use a T30 Torx and remove the screw holding the pipe in the housing (red arrow).

Use a 5mm Triple Square and remove the bracket for the coolant hose and pipes (red arrow).
Figure 18

Use a 5mm Triple Square and remove the bracket for the coolant hose and pipes (red arrow).

Pull the wiring loom from the bracket (yellow arrow) and then remove the second 5mm Triple Square (red arrow).
Figure 19

Pull the wiring loom from the bracket (yellow arrow) and then remove the second 5mm Triple Square (red arrow).

Use a screwdriver and gently pry the pipe out from the housing (red arrow).
Figure 20

Use a screwdriver and gently pry the pipe out from the housing (red arrow).

Remove the two 10mm bolts (red arrows) from the thermostat housing.
Figure 21

Remove the two 10mm bolts (red arrows) from the thermostat housing.

Pull the housing up and out from the engine (red arrow) Note; this photo illustrates the thermostat housing and lower radiator hose coming out together as we could not get them separated in the vehicle.
Figure 22

Pull the housing up and out from the engine (red arrow) Note; this photo illustrates the thermostat housing and lower radiator hose coming out together as we could not get them separated in the vehicle.

Always replace the gasket even if you are reinstalling the old housing (red arrow).
Figure 23

Always replace the gasket even if you are reinstalling the old housing (red arrow). The housing and thermostat are one piece and have to be replaced together. Installation is the reverse of removal, and don't forget to refill your coolant.

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Comments and Suggestions:
Dano Comments: Very Good information. I think it like taking a apart a Mickey Mouse Watch very tight pieces. Thank You
September 2, 2016
  Followup from the Pelican Staff: HAH yes. - Nick at Pelican Parts  
Hk Comments: Just had to say thank you so much for this information, I followed this step by step...it wasn't pleasant but I was able to get the job done myself and saved alot of money. Really the things that take the longest aren't skill related, but more so frustrating things like removing clamps and stuck hoses etc. Still totally doable. BTW spraying WD-40 where the alternator attaches to the engine helps a lot with removal/re-install.
April 2, 2016
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Alex Comments: My name is Juan I have 2006 VW GTI but my heater not working I chance of panel control and blower motor and not working what may be
March 2, 2016
  Followup from the Pelican Staff: Could be a faulty water pump, if there is not hot coolant flow. Or a faulty blower motor /resistor if there is not air flow. - Nick at Pelican Parts  
Joeycarnuba Comments: One thing to note, my alternator was very tight. After removing the two bolts that hold it on it would not budge at all, I had to use some WD40 on the contact points and then carefully use a pry bar to budge it loose. Once loose enough to jiggle out off its contact points I found it easier to remove the alternator by removing the tension pulley. I also removed two top bolts on my motor mount and raised my motor with the use of a floor jack a couple of inches for added clearance, this made it easier to remove the alternator.
January 21, 2016
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
Joeycarnuba Comments: Where can I find a replacement pipe that slides into the thermostat shown in picture 20?

PS. I agree that this project is a major pain and takes a lot of patience, I wish I would have found these instructions before I did mine.
January 20, 2016
  Followup from the Pelican Staff: Pelican Parts. Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Arnet1990 Comments: This job was not fun, everything was stuck and there was little working room. To top it all off the brand new thermostat I purchased wahler brand was faulty and leaked in the lower seal before the quick connect. Not sure if there is a easy way to check the factory seals but I recommend doing so before putting it all back together. Other then that this review was very helpful.
January 12, 2016
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
Woodyteacher Comments: Can I assume that this is pretty much the same procedure for the non turbo FSI 2.0 - just ignore the sections that relate to the turbo ?

Sensational write up ... Very helpful.
December 21, 2015
  Followup from the Pelican Staff: I think they are different. You can use it as a rough guide though. - Nick at Pelican Parts  
Mauro Comments: Thanks for this manual, great help!

A little note:
Make sure that when fitting the tube showing on picture 17 or 20 it's aligned correct before fasten the screw on picture 19.
If it's not aligned correct, coolant will leak from here and you need do loosen everything again.
September 25, 2015
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
rik Comments: Can I run my mk 4 golf with out a thermostatic valve for a short while iv replaced the head gasket and she's still boiling the water away and overheating no more money
May 10, 2015
  Followup from the Pelican Staff: First check that the cooling system is bled properly. Then check if the water pump is faulty. If it is not, the head gasket may still be faulty. - Nick at Pelican Parts  
Jay Comments: Great write-up. Very helpful.

Regarding the bottom hose when you're trying to pull it off the thermostat housing, it's just easier to disconnect that bottom radiator hose and pull it all out.
March 28, 2015
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
galavoxx Comments: I consider myself a fairly skilled shade tree mechanic but this job took me five hours. It's how these projects play out sometimes. Every difficulty that I could have, I did have. Stuck clamps, stuck hoses, difficult alternator removal and install, this job is a pain. The only thing that went smoothly was the serpentine belt install and removal. Thank you Pelican for the great instructions. I saved myself 900 dollars.
January 31, 2015
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
sandeep Comments: my fans are staying on evn on start up
October 20, 2014
  Followup from the Pelican Staff: The coolant temp sensor may be faulty. - Nick at Pelican Parts  
texasmkv Comments: Note; our coupling would not separate no matter what we tried

I felt the same way. Got frustrated and grabbed the bottom part and put all my force onto the thermostat, it finally came loose. I also sprayed it with liquid wrench to give it some lube
September 24, 2014
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 

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