Loosing Coolant

[Stevieb03]

Hi all, hopefully somebody will be able to give me some advice on a coolant problem
I've noticed that my coolant levels keep dropping to below min, I'll top up and within about 3 weeks it's dropped again an I'm only doing short journeys to work and local area; no obvious signs of a leak, pressure cap seems to be ok and hisses when I remove it, and not noticed any white crap in the oil filler cap or dip stick indicatin a head gasket problem
Can anybody suggest what else I can try / look at?
Thanks

Steve

[TimDogg]

Mate, I've always had this too - I just think that the RS4 eats coolant which is odd but I live with it.

[Stevieb03]

It can't 'eat' that much coolant in 3 weeks, I would understand if it was really long journeys but at less than 50 miles a week there must be a problem?

[mmdr7qam]

Check for a possible auxillary radiator leak. I found that my coolant level was dropping with no obvious reason evident and found both of my auxillary radiators to have corroded slightly resulting in leaking coolant. My understanding is that this a fairly common issue as these cars get older.

[sonny]

Check for a possible auxillary radiator leak. I found that my coolant level was dropping with no obvious reason evident and found both of my auxillary radiators to have corroded slightly resulting in leaking coolant. My understanding is that this a fairly common issue as these cars get older.

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[TimDogg]

Right, I'll have a look at the aux rads then, crikey - people are sooo touchy

[adsgreen]

Check for a possible auxillary radiator leak. I found that my coolant level was dropping with no obvious reason evident and found both of my auxillary radiators to have corroded slightly resulting in leaking coolant. My understanding is that this a fairly common issue as these cars get older.

This

+1

The coolant system on the RS4 is completely sealed so you shouldn't get any loss. Sure, a little here and there over a number of years but there is no way you should be expecting to top up between annual services (and even then I'd be looking for a leak).

The thing to remember with the Aux rads is that they (at least one of them) are thermostat controlled and I don't know what temperature they open at but it's quite high.
As such if one has a problem it is entirely possible to not have any leak until you get caught in stop/start traffic and the coolant temp starts to climb.

The best way to check is go for a town drive long enough to get the oil up to 100c or above then come back home and let the car idle. If you have an odb/vag-com then you can obtain the exact coolant temperature (the dash lies - it's hardly ever 90c ). If you can wait for the coolant fan to come on then all the better. Then grab a torch and start looking down the vents to the rads - it's usually pretty easy to spot a ailure as they weep pretty badly. Especially if you are losing that much coolant.

Get it looked at and whilst the bumper is off you might as well:
- get the bumper gap sorted
- if the drivers side failed then replace with a cold air feed. Cheaper and you won't have any more coolant issues from that side.
- if the passenger side failed then hell... might as well still get the cold air feed as it'll be cheap with the bumper already off!

Oh - the other thing is that the coolant loss will look worse than it is. When there is a good seal the pressure will stop the coolant boiling and limit it's expansion. As soon as you have a failure the pressure won't be maintainable and the coolant will expand (possibly even chuck some out of the expansion tank).

[guffy]

Same symptoms i had, both aux rads changed.

[Stevieb03]

Excellent response, thank you guys so much... I'll have a look, one think I havent ever noticed the fans coming On for cooling, even after a blast around a track or switching engine off the car is silent, is that normal?

[stu]

That's some great explaining. Worthy of a sticky IMHO. Linky in the FAQs? Any hands?

[P_G]

The other thing to do to prolng the life of your rads is to regularly jet wash through the bumper grilles to keep the crud away from them, especially in winter because salt and leaf mulch corrodes them quicker. Also a common problem in B6 S4's. Having just done the aux. rad delete I had mine both checked and they were fine after nearly 6 years and 90k+ miles. All about mechanical sympathy and regular use.

[adsgreen]

That's some great explaining. Worthy of a sticky IMHO. Linky in the FAQs? Any hands?

np - will re-do as a faq later in a new thread and post link.

[Stevieb03]

Thanks again, my next question will be if anybody has done the air flow mod can I buy their old rad incase the otherside is Knakered lol

[adsgreen]

Thanks again, my next question will be if anybody has done the air flow mod can I buy their old rad incase the otherside is Knakered lol

Dont' bother. They are cheap at about 100 quid each and very very fragile.
When my pax one went I had the drivers one moved over and the cold air feed done. Within 2 days it was leaking too even though it looked fine with no sign of previous leakage.

[stu]

That's some great explaining. Worthy of a sticky IMHO. Linky in the FAQs? Any hands?

np - will re-do as a faq later in a new thread and post link.

good stuff.