DIY: B6 A4 1.8T - Thermostat Replacement

[eljay]

Was this with an OEM thermostat? Or what was the brand?

[fabric8]

Was this with an OEM thermostat? Or what was the brand?

It wasn't OEM, and I don't recall if it had a brand. This is what I bought: clicky

[cleoo]

My thermostat was leaking coolant and my coolant gauge was incorrectly showing the wrong temperature.

I installed the ECS Thermostat Kit, which included the o-ring for the hard coolant pipe, but does not include the J-plug, which I bought.

I removed the intake manifold and had better access to the thermostat without having to remove the alternator since I was already changing the PCV with the 034 Kit.

I used a 10mm socket and extension to remove the thermostat bolts.

I unbolted the 13mm bolt on top of the oil filter.

I removed the orange dipstick tube so I don't break it when pulling out the thermostat.

My old thermostat part number was 06B 121 111 G made in 2006 according to the imprint.

The ECS comes with the newer 06B 121 111 K.

I used a screwdriver to coax out the J plug.

















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[myfreeaudi]

This is one of the very best DIY articles I have ever seen. My current problem is a leak and this shows me exactly where to look (while reminding me that some areas are not easy to see).

Question: what is the j plug for? Does it conduct coolant or serve as a thermostat bypass?

Thanks,

John

[old guy]

This is one of the very best DIY articles I have ever seen. My current problem is a leak and this shows me exactly where to look (while reminding me that some areas are not easy to see).

Question: what is the j plug for? Does it conduct coolant or serve as a thermostat bypass?

Thanks,

John

The J plug simply plugs up a hole that is used for a coolant hose connection when the block is used for a transverse application.

[myfreeaudi]

Thank you for this wonderful write up. I have a leak which I cannot find so may be thermostat. If so, this write up makes me somewhat lss depressed about having to replace it before the holiday road trip.

Thanks again.

[steve53mg]

Is removal of the J plug a must?

[MMMB00ST_A4]

Is removal of the J plug a must?

Strongly recommended. It is 7/10 times the culprit for any leaks in the area. That, and it's under $10, so why not while you're 99% of the way there?

[JAudi23]

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

I might need to do this soon, question about loosening the tensioner/readjusting the tensioner when done.

Is this simply loosening and then tightening again, or when retightening, do you need to put a certain tension on the belt?

How do you know how much to tighten it up?

Is there a way to mark a line on the tensioner before loosening, then tightening up again to that same position?

[customa4]

I might need to do this soon, question about loosening the tensioner/readjusting the tensioner when done.

Is this simply loosening and then tightening again, or when retightening, do you need to put a certain tension on the belt?
Simply relieving tension with a 17mm wrench and then once the wrench is removed, the proper tension is applied. Nothing more...
How do you know how much to tighten it up?
N/A - just relieve tension and all is well
Is there a way to mark a line on the tensioner before loosening, then tightening up again to that same position?

Unnecessary. Just use a marker pen to mark the direction of the belt. When you remove the belt, just remove it from the alternator, leave it configured on the rest of the pulleys so you only have to put it back over the alternator and you're done.
Make sure you have a replacement j-plug if you're replacing the thermostat.

[iamshayan]

also fwiw. the alternator doesn't have a 'grounding strap' going to it - as mentioned in the writeup lol... its a live 12v+ from the battery/starter. that's the cable that charges the battery.

If you haven't disconnected your battery and your short that out you're going to start gypsy welding and it's not going to be a good time. I can't believe it has been this many years and no one caught that. - even you old guy. Calling you out here.

[old guy]

LOL!!!

Hangs head in shame....

[gottaBdope]

Wow. I'm impressed this thread is still going!

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[RAUDI-Ä4]

Wow. I'm impressed this thread is still going!

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me too haha. started this the other night but my one alternator bolts was completely stripped so I ordered a new bolt and am gonna do the dipstick tube while I'm already in there.

[Elbeam]

I'm getting ready to do this as I started getting the P1293 fault recently. As this will be my first time (pretty new to audi), is there anything else I should be looking to change out while I'm in there? I'm planning to do the coolant flange, j-plug, serpentine belt, and oil dipstick tube.

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[JAudi23]

I'll be doing this very soon, possibly this weekend. Anything else in there I should be changing while it's taken apart?

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[JAudi23]

Completed this today as well, and am extremely grateful for this DIY and everyone's helpful comments.

Changed the thermostat, oil dipstick tube and the J-plug.

The thermostat, the J-plug, and the dipstick tube all had pieces crumbling in my hands as I was removing them from the engine.

Fingers crossed, this solves the latest error codes I've been getting.

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[captainplanet]

I've used this DIY numerous times over the years, and wanted to updated it with a little more info.

You can get an aluminum J-Plug which doesn't break down in the flow of the coolant: https://www.ecstuning.com/b-ecs-parts/billet-aluminum-coolant-j-plug-w-o-ring/005224ecs01a/

I've been using it for years without a leak.

The o-rings used on the coolant return hard pipe from the heater core to the thermostat AND the j-plug are the same - 20x3 millimeters.

When putting things back together, tighten the thermostat first and ensure it is seated properly. Then tighten the coolant return hard pipe from the heater core, then put back in that hard to reach bolt on top of the engine securing the hard pipe to the flange. Doing so in any other order can cause a leak. Don't ask me how I know.

[A4SoftWalker]

I've used this DIY numerous times over the years, and wanted to updated it with a little more info.

You can get an aluminum J-Plug which doesn't break down in the flow of the coolant: https://www.ecstuning.com/b-ecs-parts/billet-aluminum-coolant-j-plug-w-o-ring/005224ecs01a/

I've been using it for years without a leak.

The o-rings used on the coolant return hard pipe from the heater core to the thermostat AND the j-plug are the same - 20x3 millimeters.

When putting things back together, tighten the thermostat first and ensure it is seated properly. Then tighten the coolant return hard pipe from the heater core, then put back in that hard to reach bolt on top of the engine securing the hard pipe to the flange. Doing so in any other order can cause a leak. Don't ask me how I know.

The entire DIY and this little snippet of information about torquing the thermostat down 1st before the hard pipe was very essential to helping me get the job done right the 1st time.

[Nickadams]

About how long did it take you to replace the thermostat and J plug? I am thinking of doing this soon. Thanks

[Elbeam]

About how long did it take you to replace the thermostat and J plug? I am thinking of doing this soon. Thanks

I took my time and did alot of other things when I did my T-stat and J-plug. Made it really easy taking the intake manifold, fuel rail off. If new to the job Id allot about 5-6 hours. And make sure you have all the tools and hazmat needed, especially if its your daily driver.

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[Nickadams]

Thanks - maybe next weekend.