B7 A4 Avant 2.0 - Lost heat today while driving, white gunk in coolant reservoir tank

[Joeymac18]

Cars been running, idling and performing fine. Ran a few errands today with the heat blasting hot, by the end of my errands it was blowing cold air. No overheating or known issues there

Got home let the car cool down and checked coolant reservoir and noticed it was full of this white, frothy gunk. Not creamy white like I’ve seen typical of when oil is in there. But frothy white gunk, kind of looked like that stuff that builds up in creeks you see when your a kid playing in the woods lol. It was in both of the lines going into the coolant reservoir as well.

https://uploads.tapatalk-cdn.com/20250121/b918950431e9e65c55f69779b02dfbdc.jpghttps://uploads.tapatalk-cdn.com/20250121/0e416836db8db5996b8c9764ad64d7ce.jpghttps://uploads.tapatalk-cdn.com/20250121/8f9a34e4c9f1bf5dd9edcfc988661327.jpghttps://uploads.tapatalk-cdn.com/20250121/e653996c422b396d196ac9357108570e.jpghttps://uploads.tapatalk-cdn.com/20250121/a72405a40849c64827f01dab3620178f.jpghttps://uploads.tapatalk-cdn.com/20250121/48141784fbaadbb4e5b4088ed2fde813.jpg





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[CycloSteve]

Did someone use bars-leak at some point? My son's B6 had that gunk in there from the PO hiding a water pump seal leak. Comes back to haunt you when the heater core, radiator, block, hoses and lines are all clogged.

I found a similar tan gunk in the oil cooler when I replaced it in my B7, though everything else looked fine.

[Joeymac18]

Not that I know of! This car was enthusiast owned by a very trusted friend. And within my ownership now of [emoji6[emoji640][emoji637]]+ years I’ve never used that stuff! Unless one of the shops I use did without my knowledge, but I highly doubt that.

I’m not sure where to start with diagnosing this issue. If anyone has any insight on what this could be, or what would cause that I’d appreciate the help!


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[Joeymac18]

Check engine light is on. Scanned the car and I’m getting codes

P[emoji638][emoji[emoji6[emoji640][emoji638]][emoji640][emoji6[emoji640][emoji638]]][emoji[emoji6[emoji640][emoji638]][emoji640][emoji6[emoji640][emoji638]]][emoji640] & P[emoji638][emoji637][emoji[emoji6[emoji640][emoji638]][emoji640][emoji640]][emoji637]

[Joeymac18]

Codes stored in care are
P 2 0 0 4 and P 2 1 8 1

New to using this mobile app, not sure why last post showed up as emoji codes


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[maurizio]

time to replace every hose that coolant touched

[Joeymac18]

[emoji6[emoji640][emoji637]][emoji637][emoji639][emoji640][emoji640][emoji[emoji6[emoji640][emoji638]][emoji640][emoji6[emoji640][emoji637]]][emoji637]]time to replace every hose that coolant touched

Making a parts list now! Should I figure out what’s causing this problem before replacing the hoses and flushing the system out?Would you recommend doing the thermostat and oil cooler as well?


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[CycloSteve]

time to replace every hose that coolant touched

You can try to flush, but likely your radiator, heater core, and oil cooler are plugged too.

One other way which I have seen this happen is when different coolant types are mixed and a chemical reaction produces a precipitate (gunk). Never ever mix green with red.

[Theiceman]

looks like you mixed OAT and IAT coolant types.. thats bad news..

[Joeymac18]

[emoji6[emoji640][emoji637]][emoji637][emoji639][emoji640][emoji[emoji6[emoji640][emoji638]][emoji640][emoji639]][emoji640][emoji640]]looks like you mixed OAT and IAT coolant types.. thats bad news..

I don’t think I’ve ever mixed coolant types. I’ve owned the car for [emoji6[emoji640][emoji638]] years now and this is all I’ve ever put in the vehicle?
https://uploads.tapatalk-cdn.com/[emoji638][emoji[emoji6[emoji640][emoji638]][emoji640][emoji6[emoji640][emoji638]]][emoji638][emoji6[emoji640][emoji637]][emoji[emoji6[emoji640][emoji638]][emoji640][emoji6[emoji640][emoji638]]][emoji637][emoji638][emoji638]/e[emoji638]d[emoji[emoji6[emoji640][emoji638]][emoji640][emoji639]][emoji[emoji6[emoji640][emoji638]][emoji640][emoji6[emoji640][emoji638]]][emoji637]a[emoji[emoji6[emoji640][emoji638]][emoji640][emoji639]][emoji[emoji6[emoji640][emoji638]][emoji640][emoji6[emoji640][emoji637]]][emoji640]be[emoji639][emoji[emoji6[emoji640][emoji638]][emoji640][emoji6[emoji640][emoji638]]]ec[emoji637][emoji638][emoji640][emoji[emoji6[emoji640][emoji638]][emoji640][emoji640]][emoji[emoji6[emoji640][emoji638]][emoji640][emoji639]][emoji639][emoji639]e[emoji637][emoji[emoji6[emoji640][emoji638]][emoji640][emoji6[emoji640][emoji638]]]b[emoji[emoji6[emoji640][emoji638]][emoji640][emoji640]]cc[emoji638][emoji[emoji6[emoji640][emoji638]][emoji640][emoji6[emoji640][emoji637]]].jpg


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[Joeymac18]

https://uploads.tapatalk-cdn.com/20250122/89234353834d4063851bd007472223c0.jpg


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[Joeymac18]

After cleaning out and emptying the reservoir tank the other night, I put clean new coolant in. I drove to work and back yesterday and let the car cool, checked the reservoir tank to see what it looked like and if it had gathered and cleared out any gunk from the lines. No white gunk, but the coolant in the reservoir went in pink and now has an amber/orangish color. Could be residue from the inside of the tank and the lines. I’ve been told it’s probably a bad oil cooler and thermostat.

Ordered new silicone lines, an oil cooler and cooling system refresh kit. Which has a new reservoir tank, thermostat and additional coolant.

Going to flush out the heater core and cooling system before installing new items. Really wish I knew what was causing it.

https://uploads.tapatalk-cdn.com/20250122/11f12b427decc90a69acc1cfb0ed73ac.jpg


https://uploads.tapatalk-cdn.com/20250122/c95372c9696b33fbcd32f99c53dc1b20.jpg






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