Leak = trouble?

[MikeFish]

How desperate is this job to get sorted saying it is aux rad?

Depends how bad it is? Even if it is really bad, if you avoid running the engine really hot then it won't even kick in.
I only ever noticed mine steaming when sitting in traffic for 20 or 30 mins (when car was already at normal operating temperature) or sitting with the engne on parked for ages. Normal driving I never noticed it.

[MikeFish]

PS, I also get a little steam from the front during damp weather when the engine is at temp but not really hot, so defo not the aux rads. I assumed it either the main rad or just rain water evaporating on the negine parts. As I don't seem to be losing any fluid and it never happens in the dry I have to go with the rain water assumption.

[adsgreen]

You will be losing coolant.
This isn't great but manageable if you keep topping up.

Bad part is that the coolant system is no longer sealed so it won't maintain pressure. This lowers the boiling point substantially so the coolant could start to boil and this reduces the effectiveness and can be a problem.

[MarksRS]

Where would be the best place to order a replacement aux rad? By the sounds of it a few of us may need one!

[MikeFish]

Where would be the best place to order a replacement aux rad? By the sounds of it a few of us may need one!

Audi Pardner alreayd stated Stoke Audi do them for £189 delivered. Sounds about right. Might be worth a look on ebay as Aberdeen Audi sometimes do some cheap parts on there. Probablty worth having a look on EuroCarParts too especially with a 30% that's normally knocking around.

[Audi Pardner]

The definitive sign of a leaking rad is coolant loss as adsgreen says. I've just replaced both my aux rads recently (see 'F-F-Flippin' RS4s' thread) as they were the original ones, and replacing only the leaking one is bound to prompt the other to start leaking as soon as you get the bumper back on.

Or you could go down the CAF route.

[coffey555]

I had both aux radiators replaced last year and I noticed a puddle of water just in front of the passenger side wheel last week about 5 mins after I parked the car.

Had the air con on so assumed it was just condensation dripping off the condenser.

Will have to have a proper look now the next time it does it but my coolant level has ok the last time I checked.

[Audi Pardner]

I had both aux radiators replaced last year and I noticed a puddle of water just in front of the passenger side wheel last week about 5 mins after I parked the car.

Had the air con on so assumed it was just condensation dripping off the condenser.

Will have to have a proper look now the next time it does it but my coolant level has ok the last time I checked.

Yep, likely to be condensation; I've noticed a small puddle on the garage floor under the car after a run with the aircon on.

[chrisd31]

is it necessary to have the aux rads then?

[Audi Pardner]

is it necessary to have the aux rads then?

Not sure. I suspect they're there for cars running in hotter climates eg California. As far as I know, the CAF option (ie removing the o/s aux rad to accommodate a CAF) doesn't create overheating problems in our climate, but those who've done it may be able to advise properly.

[MikeFish]

I've only had the one aux rad for the last 2 summers with no issues. There are supercharged cars also running with one aux rad and had no issues I'm aware of. Possible they were just over engineered or the more common conception is as stayed above that the UK climate just doesn't need that much cooling.

[RossDagley]

is it necessary to have the aux rads then?

Not sure. I suspect they're there for cars running in hotter climates eg California. As far as I know, the CAF option (ie removing the o/s aux rad to accommodate a CAF) doesn't create overheating problems in our climate, but those who've done it may be able to advise properly.

I've done two 'ring trips now this year after a CAF and aux delete with no ill effects. Seems fine for me.

[S4Player]

Many a supercharged guy been driven hard and for many miles with no ill effects. Don't see there being any issues for an NA car

[adsgreen]

One owner from Germany did report higher than average temps when doing extended autobahn work so fabricated a mount for the replaced aux rad in front of the main rad. seemed to do the trick.
However flat out the autobahn is incredibly tough with regards to heat esp as the RS4 doesn't really have a long 6th.
But for the UK and trackdays I don't see the aux rad delete as any problem. Even if something did go wonky, you would still have the protection from the coolant gauge and warning lights well before any damage would occur.