One overheat story s8 4.0tfsi

[Ceff]

Last weekend im with family had a few days vacation in Pensacola. Friday 9 pm we moved back to Chicago and after 15 mins drive got engine overheat warning 🤦*♂️😬 quick look — no coolant circulation, lower radiator pipe cold, means, obviously, thermostat failure.



Luckily its happened earlier than when we was in the middle of nowhere. So drove back to city, left family at hotel, drove car with heater full on to Audi dealer at night to avoid traffic.



Saturday. 9 pm. Audi dealership have no thermostats in stock. Checked stores — sooner i can get it — Wednesday.



Drove some local repair shop. Brief diagnostic — thermostat failure (pretty obvious, lower rad pipe cold). Double checked local parts stores — still bad news. Deep breathing, left place and drove to nearest uhaul, thinking how to tow car back to Chicago.



Let me skip frustration and googling part, now how i fixed it. Few google topics reveal some mystery — ppls replacing thermostats on these cars and still getting overheat issues. (https://www.audiworld.com/forums/a8-...ating-2928903/)

So i took closer look at 4.0tfsi engine coolant system design (pages 46-50)
Disconnected coolant valve, plug vacuum port — viola!! This is it — sticking coolant valve (N489 page 50) switch! Idled abt 20 mins all good, drove around, refueled — all okay. 15 hrs drive and we at home. So, before replacing pump/tgermostat — i reccomend to do this simple check, looks like its pretty common but overlooked failure. Now driving like that -- its coming to operational temp noticeable longer, but car at least driveable until waiting for n489 valve.

Thermostat is mechanical with ADDITIONAL heater to open sooner, virtually bulletproof.

https://www.audiworld.com/forums/att...self-study.pdf

[09S5]

Glad you got the car fix.

Sent from my SM-N976V using Tapatalk

[qcrazy]

This is a common problem. The actual failure is the vacuum actuator...which sadly causes the whole peice to become a paperweight.

Disconnecting the vacuum line is the key to this short term repair. What happens is the vacuum actuator (N489) gets jammed opened. This causes vacuum to always be applied to the switching valve, keeping it closed and overheating the engine.

Unfortunately on the 4.0T, the N489 is incorporated into the switching valve so the entire unit needs to be replaced. And the switching valve is in a poor location, so this is a pain. It ends up being an expensive repair for a cheap part failure.

The N489 on the C7/B8 3.0T and the B9 3.0T is actually a separate part. If one was so inclined this could be fixed by just relocating a new, separate N489 to a more accessible location and just abandon the 4.0T N489 in place. An advanced repair for sure, but more economical and a longer term fix as well.

[oripaamoni]

This is a common problem. The actual failure is the vacuum actuator...which sadly causes the whole peice to become a paperweight.

Disconnecting the vacuum line is the key to this short term repair. What happens is the vacuum actuator (N489) gets jammed opened. This causes vacuum to always be applied to the switching valve, keeping it closed and overheating the engine.

Unfortunately on the 4.0T, the N489 is incorporated into the switching valve so the entire unit needs to be replaced. And the switching valve is in a poor location, so this is a pain. It ends up being an expensive repair for a cheap part failure.

The N489 on the C7/B8 3.0T and the B9 3.0T is actually a separate part. If one was so inclined this could be fixed by just relocating a new, separate N489 to a more accessible location and just abandon the 4.0T N489 in place. An advanced repair for sure, but more economical and a longer term fix as well.

I am having the same issue on my RS7, I am going to attempt what you suggested above. Any chance you have the part number for the N489 from the 3.0T.

Also I am having a hard time even seeing the N489 on my car, how were you able to access this on your car while away from home? I am thinking maybe you had more room to work with in the engine bay since you are working with an S8

[qcrazy]

Part number on the B9/C8 is 037-906-283C. You would have to confirm that the electrical connector is compatible.

I had mine fail on my S6 while on vacation back in August. I had to fix it on the side of the road. It is not easy, but can be done. I posted about it on the 4.0T forum. I just fully disconnected the vacuum line and have driven that way since August with no issues. I have no plans to ever hook it back up. It is a totally unnecessary piece.

To get access, pop the hood and pull the cover between/above your radiator and bumper. With that off there is a small deflector just to the right of the airbox intake. That should be held on with 3x T30 bolts. With the deflector off you will be able to see a little bit of the front of the engine.

Towards the center of the engine you will be able to see just the top of the switching valve. There will be a small section of rubber vacuum line connected to it. Use a long needle-nose and pull the rubber vacuum line out. Grab a golf tee and plug the vacuum line. That is it...you are done. Put everything back together.

If you don't ever plan on hooking it back up, I recommend putting a small amount of silicone on the vacuum port on the valve on the engine, just to keep anything from getting inside.

P.S. Leave the electrical connector hooked up when pulling the vacuum line.

[oripaamoni]

Thank you so much for the reply! I am going to get after it later today. Hopefully that solves my problem!

[qcrazy]

No problem. Let us know if it works for you.

[oripaamoni]

No problem. Let us know if it works for you.

This thread saved me a load of pain and diagnostics, Thank you! I ended up cutting the vacuum line in the middle and then inserting a solid plastic stick inline. Went for a drive and the oil temp took a long time to reach operating temperature but the car never overheated! I am going to try see if I can fit a stand alone N489 from another model as you suggested above. I will let you all know how it goes.

Do you think I should try to get the N489 from a 3.0T rather than the newer B9/C8 solenoid that you mentioned above?

[qcrazy]

The B8/C7 3.0T may use the same part, I just couldn't find it searching quick. I always carry a spare one in my B9...just in case...so I knew that number already. I wouldn't be surprised if it is the same part, I just have been unable to confirm.

[IceyTys]

Last weekend im with family had a few days vacation in Pensacola. Friday 9 pm we moved back to Chicago and after 15 mins drive got engine overheat warning 🤦*♂️😬 quick look — no coolant circulation, lower radiator pipe cold, means, obviously, thermostat failure.



Luckily its happened earlier than when we was in the middle of nowhere. So drove back to city, left family at hotel, drove car with heater full on to Audi dealer at night to avoid traffic.



Saturday. 9 pm. Audi dealership have no thermostats in stock. Checked stores — sooner i can get it — Wednesday.



Drove some local repair shop. Brief diagnostic — thermostat failure (pretty obvious, lower rad pipe cold). Double checked local parts stores — still bad news. Deep breathing, left place and drove to nearest uhaul, thinking how to tow car back to Chicago.



Let me skip frustration and googling part, now how i fixed it. Few google topics reveal some mystery — ppls replacing thermostats on these cars and still getting overheat issues. (https://www.audiworld.com/forums/a8-...ating-2928903/)

So i took closer look at 4.0tfsi engine coolant system design (pages 46-50)
Disconnected coolant valve, plug vacuum port — viola!! This is it — sticking coolant valve (N489 page 50) switch! Idled abt 20 mins all good, drove around, refueled — all okay. 15 hrs drive and we at home. So, before replacing pump/tgermostat — i reccomend to do this simple check, looks like its pretty common but overlooked failure. Now driving like that -- its coming to operational temp noticeable longer, but car at least driveable until waiting for n489 valve.

Thermostat is mechanical with ADDITIONAL heater to open sooner, virtually bulletproof.

https://www.audiworld.com/forums/att...self-study.pdf

Between you and @qcrazy you both saved me so much time and headache......#grateful. I had a similar problem a few weeks ago, overheated and had to get towed home. I spend weeks trying to figure out what was going on, because I just had my PCV valve replaced under Audi extended warranty and the overheating issue just started to show up. After doing some research, I was convinced the 1st culprit had to be the T Stat. I went out and bought a Tstat and was about to start my journey of getting under the car (already had the bottom covers removed previously) when I decided to keep searching the forums. Then I saw this post.....this morning I figured, what do I got to lose....... and VOILA!!!!! Mystery solved....pulling the vacuum hose and plugging it worked like a champ!!! MANY THANKS!!!

Now how either one of you made this repair on the side of the road is beyond me, unless you had a set of tools with you......LOL

I am curious these posts are a year and a half old......did you ever get the repair of the valve done, or just leave it as-is????

THANKS AGAIN

- - - Updated - - -

No problem. Let us know if it works for you.

See my above posts.....Many thanks!!!

[ElementR]

Yet another thx to Qcrazy which just saved me a ton of work! My thread here: https://www.audizine.com/forum/showt...3#post15060423

[Ceff]

Any “thank you” in any BTC amount will get u karma skyhigh

Btc address to send:

bc1qv3j7tvgdg06y7jjkxgj5e74wvnunaetefrm6l2

(Im posting it to all my old threads helped ppls to gather some help for someone)

[Ceff]

Between you and @qcrazy you both saved me so much time and headache......#grateful. I had a similar problem a few weeks ago, overheated and had to get towed home. I spend weeks trying to figure out what was going on, because I just had my PCV valve replaced under Audi extended warranty and the overheating issue just started to show up. After doing some research, I was convinced the 1st culprit had to be the T Stat. I went out and bought a Tstat and was about to start my journey of getting under the car (already had the bottom covers removed previously) when I decided to keep searching the forums. Then I saw this post.....this morning I figured, what do I got to lose....... and VOILA!!!!! Mystery solved....pulling the vacuum hose and plugging it worked like a champ!!! MANY THANKS!!!

Now how either one of you made this repair on the side of the road is beyond me, unless you had a set of tools with you......LOL

I am curious these posts are a year and a half old......did you ever get the repair of the valve done, or just leave it as-is????

THANKS AGAIN

- - - Updated - - -



See my above posts.....Many thanks!!!

😘 ))

[sohail_anwar]

Hi Guys,

Need help .. I am facing the same issue with my 2013 Audi A8L , where the engine temperature heats up while driving after 15 mins or so.
Then I see the the coolant fluid leaking below. I have had the mechanic do the pressure test and there is no leak. I have read through all the post and folks say that it could be a stuck thermostat but reading your post makes me think that I can try your solution. But for guy like me who is not handy with cars, how would I get a mechanic or car shop do what you are suggesting? What do I basically tell them to do?

Any help will be much appreciated.

Thanks

[sohail_anwar]

Last weekend im with family had a few days vacation in Pensacola. Friday 9 pm we moved back to Chicago and after 15 mins drive got engine overheat warning 🤦*♂️😬 quick look — no coolant circulation, lower radiator pipe cold, means, obviously, thermostat failure.



Luckily its happened earlier than when we was in the middle of nowhere. So drove back to city, left family at hotel, drove car with heater full on to Audi dealer at night to avoid traffic.



Saturday. 9 pm. Audi dealership have no thermostats in stock. Checked stores — sooner i can get it — Wednesday.



Drove some local repair shop. Brief diagnostic — thermostat failure (pretty obvious, lower rad pipe cold). Double checked local parts stores — still bad news. Deep breathing, left place and drove to nearest uhaul, thinking how to tow car back to Chicago.



Let me skip frustration and googling part, now how i fixed it. Few google topics reveal some mystery — ppls replacing thermostats on these cars and still getting overheat issues. (https://www.audiworld.com/forums/a8-...ating-2928903/)

So i took closer look at 4.0tfsi engine coolant system design (pages 46-50)
Disconnected coolant valve, plug vacuum port — viola!! This is it — sticking coolant valve (N489 page 50) switch! Idled abt 20 mins all good, drove around, refueled — all okay. 15 hrs drive and we at home. So, before replacing pump/tgermostat — i reccomend to do this simple check, looks like its pretty common but overlooked failure. Now driving like that -- its coming to operational temp noticeable longer, but car at least driveable until waiting for n489 valve.

Thermostat is mechanical with ADDITIONAL heater to open sooner, virtually bulletproof.

https://www.audiworld.com/forums/att...self-study.pdf

Hi there,

Need help .. I am facing the same issue with my 2013 Audi A8L , where the engine temperature heats up while driving after 15 mins or so.
Then I see the the coolant fluid leaking below. I have had the mechanic do the pressure test and there is no leak. I have read through all the post and folks say that it could be a stuck thermostat but reading your post makes me think that I can try your solution. But for guy like me who is not handy with cars, how would I get a mechanic or car shop do what you are suggesting? What do I basically tell them to do?

Any help will be much appreciated.

Thanks

[LennyClickedIt]

YOU FIXED IT FOR ME !!!! Married with 6 grown kids - current owner of A8L D4 4.0T TCU tune, Ds-1 and the mods, Sq5,A4 Cabrio, VW Tdi Toureg, VW CC 3.6 AWD - RossTech VDS etc. So I love and know this brand of vehicles…same issue identical circumstances (overheating) on a return trip 4 hour drive (not 15 like yours) - rented a car drove home - grabbed my F-250 and a trailer and hauled ass back to New Orleans from Houston - trailered A8 home. My son is a Mercedes Master Mechanic currently working for Mercedes - all this knowledge and thoughts were worthless - intending to replace thermoswitch, thermostat, water pump because I’m at 180K miles and never experienced a major repair (recall work of course ) THANK YOU ALL SO SINCERELY FOR SHARING INFO WITH EVERYONE!!!


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