05 S4 Gold Flakes in Radiator Fluid

[v65animal]

I bought the car in December 2017 with about 65,000 miles, in October 2018 with 69,000 miles I had the radiator fluid changed. I've never seen this stuff before. (The car has about 78,000 miles now)

Sept or Oct 2021 the alternator died, and the belt broke.

They replaced it all, then had to take it apart as the belt broke again, they replaced the tensioner and it was Ok then.

A month later (It sits a lot just a 3rd car) I noticed more oil than usual under the car. I took it back to them, they replaced the oil cooler seals.

Then a month later, I saw radiator fluid under it. They put in a new radiator from Audi, the radiator hose wouldn't line up, they ordered a new hose per Audi, it still didn't fit. The Audi said they sent the wrong radiator, so we got a new radiator. They put it all back together and it leaked worse than the original one, so they took it all apart again and put a new one in. (Feb 2022)


Yesterday I topped off the radiator overflow and noticed gold flakes on the top of the cap.

Now, my point is, I've never added stop leak, I've had the car for almost 5 years. They have recently drained and re-filled the radiator multiple times in the last year. It should be really clean.

Any ideas, I'm thinking something in the new radiator caused it. Or possibly a previous owner put in stop leak and it's just now coming out of the heater core?

Thanks,

[Zolli]

I think the gold flakes are actually copper flakes, and it’s from stop-leak solution. I think your mechanic put that in, but yes it could be from the previous owner.

The radiator for the A4 is sometimes thought to be compatible with the S4’s, but it’s not. There are also o-rings in the hoses where they connect to the radiator. They can get brittle or sometimes be mangled when slipping - I mean jamming - the hoses back on.

Personally, I think you should do a coolant flush (you’ll need like 10 gallons of distilled water and some replacement G12 coolant - not just ANY sort of coolant. The stop-leak will not save the situation, and you’ll want to pinpoint where the leak is coming from.

[v65animal]

Can you flush the radiator fluid without taking the front end off? Or putting it in the service position? Is there a lower hose that can be disconnected?

[Zolli]

Yep - the lower radiator hose can be disconnected (driver’s side), but it’s pretty messy and a tough reach. Even easier is the thermostat housing (also driver’s side) has a drain plug with a copper crush washer. It uses something like a 6mm or 7mm or 8mm hex to remove. Points straight down into your conveniently placed receptacle of choice. Be sure to install a new crush washer when you replace the plug. It’s a standard size if I recall - Ace Hardware or some similar place should have them.

Pouring in distilled water into the reservoir while you’re draining will utilize the siphoning action of the drain to pull in the water and avoid air pockets for the flushing operation. A big ol funnel helps with that. You’ll get air anyway, but it’ll get purged.