Main Radiator Differences.

[Blau_RS2]

Anybody know what the differences are between the early RS6 main radiator and the later one's? There doesn't seem to be any aftermarket options for the later one. Part number is 4B3121251F versus a D for the earlier one.

There seems to be an extra inlet for the transmission fluid possibly? Wonder if there is a way to bypass this and use an earlier Rad as the price difference is significant. ~$1100 vs $300.

[hahnmgh63]

Not sure what the difference is but I think the 'D' version is for the A6 4.2 and the 'F' version is for the RS6. I was looking to buy a spare a while back and that is what I remember in a search. Since going Manual, I might look into the dimension of the A6 Manual radiator since I don't need the tranny cooling anymore.

[nubcake]

Not sure what the difference is but I think the 'D' version is for the A6 4.2
This is correct.
Early RS6 is 4B3121251E.

[Blau_RS2]

So I assume the eBay ads showing that the D version works on the RS6 are just incorrect. Does anyone know if there is an alternative to the Audi radiator for the RS6?

[nubcake]

Does anyone know if there is an alternative to the Audi radiator for the RS6?

None that I'm aware of.

Anyway, did a bit of googling. Early RS6 rad (https://www.ebay.co.uk/itm/Audi-RS6-C5-4B3-Water-Engine-Cooling-Radiator-Cooler-Coolant-Heater-4B3121251E-/142261587437). S6/A6 4.2 rad (https://www.wolfautoparts.com/2002-2003-audi-s6-c5-42l-radiator-227192.html). They look pretty damn similar to me.
BUT!
1) Even if physical dimensions and fittings are 100% the same (and condenser mounting tabs, etc), they still might have different cores & different cooling capacity.
2) Late RS6 rad is different in that it has an extra fitting for aftercooling pump. You can get away with just plugging that, but potentially it can cook your turbos eventually.
Aftercooling systems are pretty different between early/late RS6 - they have different directions of (after)coolant flow (and late models have an extra electromagnetic valve).

Is your rad FUBAR? Or, if it's repairable, might be a best idea to just go that way.

[hahnmgh63]

They look close, would be nice to find a big part supplier or dealer that stocked both or at least get the 'D' version and see what it looks like side by side.

[Blau_RS2]

Is your rad FUBAR? Or, if it's repairable, might be a best idea to just go that way.

I'm waiting to hear from my mechanic to see if it's repairable or not. I'm hoping it can be fixed but I was just looking for other options. I haven't even seen the car yet and I'm already dealing with issues! :lovl:

[GreggPDX]

Supposedly this shop has built a custom radiator for the RS6:

https://wizardcooling.com/

You might ping them and see what they say. If they do, please post an update. I'm curious, but too lazy to do the work myself :)

[Blau_RS2]

Supposedly this shop has built a custom radiator for the RS6:

https://wizardcooling.com/

You might ping them and see what they say. If they do, please post an update. I'm curious, but too lazy to do the work myself :)

Here's an update to my search for a new radiator. I ended up going with a new Audi one from the dealer. I talked to Wizard Cooling and they said they'd be able to make a custom one but they wouldn't be able to do it with the OEM fittings and I'd have to customize the lines going into the radiator. Their radiator would have been about $1000 plus the custom lines. In the end not really a savings over the OEM Rad. I don't plan on going much more than a Stage 1 and I'm up in Canada so extra cooling wasn't really a priority.