DIY: B6 A4 1.8T - Thermostat Replacement

[Matt Devo]

I used the writeup by Mark955 on AW, but thought I'd add some pics for the more visually-oriented =)

Thermostat is part # 06B-121-111-G. my original was a -D, and I believe G is being replaced by H (as per my invoice).

the operating area:




Step 1: Drain coolant (sorry no pics)

Remove bottom belly pan. Remove coolant reservior tank cap. Remove plastic clip holding coolant sensor in place at lower radiator hose/pipe. With bucket/catch pan underneath, remove sensor and let coolant drain.


Step 2: Remove upper radiator hose

remove the small hose connecting the coolant reservior to the upper radiator hose. Then remove the larger hose from the hard pipe running along the intake and from the radiator. You'll need to pop up (but not off) the metal clip holding the hose to the radiator, then firmly pull back:



hose removed:




Step 3: Remove intake hose (throttle body-to-intercooler)

remove driver's side headlight (not necessary but makes it a lot easier). Loosen clamp at each end and remove hose.




Step 4: Remove throttle body

remove electrical connector and 4 hex bolts (5mm):



removed:




Step 5: Loosen serpentine belt and slip off of alternator

use a box-end or adjustable wrench on tensioner, pull to the right. Carefully slip belt off alternator (towards front of car). Allow to hang loose below




Step 6: Remove alternator bolts

remove 4 bolts holding alternator to bracket:




Step 7: Remove electrical connector and grounding cable from alternator

after removing the 4 bolts, lay the alternator face down on the top of the fan and remove the electrical connector, and the grounding strap. If you haven't disconnected the battery, be sure to cover the grounding strap in tape so it cannot touch other metal surfaces



alternator removed; grounding strap shown:




Step 8: Remove vertical support piece from intake manifold to block

remove the two bolts holding the support piece (6mm hex):




Step 9: Remove bolt from metal hose on t-stat; remove bolt from top of oil cooler

this will allow you to move the hard pipe away from t-stat. On my car, even after removing the bolt I was unable to remove the hard pipe at this time - I had to remove the thermostat from the block, then wiggle it free from the pipe afterwards

bolt holding the hard pipe on the right, two bolts holding the t-stat to the block on the left:



bolt holding the metal pipe to the top of the oil cooler (as seen from top of intake):




Step 10: Remove upper and lower hoses fom t-stat. Remove electrical connector on back side




Step 11: Remove 2 bolts holding t-stat to block, and remove t-stat






Step 12: Install new thermostat

install new thermostat, making sure to remove the old O-ring. The new t-stat will include a new one. I wet my finger with coolant and ran it along the O-ring to pre-lube it before installation. Otherwise, install is reverse of removal:

All done - looks just like when we started!




Disclaimer: this information is for informational purposes only. I am not responsible if you somehow manage to blow up your car in the process.

[SargeSilas]

Fantastic Post Mike - Perfect description of what I need to do. Thanks a lot!

[EuroTrashin]

i'ma be using it today

[tuner culture]

thanks for the discription - did mine this weekend and worked out perfect. _ i do recomend getting the part behind the Thermostat when you buy the thermostat, (shaped like a "J" and is held in with one bolt.) I thought the thermostat was leaking, once all taken apart, that "j" plug was the culpirt, but thanks to the audi parts specialist for telling me to replace it . When i removed the part, it came out in 3 pieces - broken plastic. I will try and get the part number a photo. the part was $10

[heywier427]

great write up. as long as your in there, change out the front knock sensor. you need to remove the thermostat to get at it, so nows a good time.

[audi_nightrider]

Sorry for reviving this thread...

I'm kinda stuck w/ removing the hose connected to the bottom part, any tips/tricks?? I keep on pushing it down and twist but won't move at all.

TIA!

[sa_seahawker]

This bolt was a serious PIA getting back in. Make sure you grab an elbow socket and long extension. I also had to dive deep under the intake and towards the motor and "feel" the bolt back into place to start it. Simply put, it's pretty hard to start a bolt at an angle with an elbow socket.

Sorry for reviving this thread...

I'm kinda stuck w/ removing the hose connected to the bottom part, any tips/tricks?? I keep on pushing it down and twist but won't move at all.

TIA!

after you pull up the metal retaining clip, you have to put some serious "stank" on it.


Great write up, btw...I approve

[jettman]

uff the screw for the thermostat fell some ware!! i cant find it. were can i get another one!!....dang precidente beer

[mexiricer]

Thanks for this write up! I did mine this morning along with the J-plug. Good thing I checked for play on the J-plug when I was swapping the t-stat. Despite no leaking from the J-plug it sheared transversly along the plug itself when i wiggled it Had to dig out some of the pieces from the block and then put in the new one In case anyone was wondering, since I just did a simple drain from the sensor (1.8T) hole and whatever spalshed out from the block when I took out the t-stat, it took me roughly a bit over a gallon of G12 to get the resevoir back to "max" fill line after repeated drive and checking. Have at least 1.5 gals on standby imo


Edit: btw be careful with that little openning of the engine block support right below the t-stat. my old J-plug fell in there and took like 20mins to get it out of there It's a tight fit but you can easily lose a screw in there too! Tape it up or just be extra careful around that area. You'll noticed it when you're there (1.8 block), hehe.