Low coolant and brown scum , causes?

[George II]

Hi, my son has a 2010 tdi manual Tiguan , and had the cooling warning light come on yesterday, upon looking it was below min in the reservoir. But there was also a lot of brown scum in the reservoir. He put some water in which enabled him to drive home from work , but is obviously worried about what caused the loss and what is causing the brown scum? The car was only serviced 2 or 3 months ago and had the timing belt and water pump replaced , could any of that be involved? He rang a mate who is a mechanic who said it might be the ERG valve , or head gasket ?
Any suggestions please ?

[h100vw]

Hi, my son has a 2010 tdi manual Tiguan , and had the cooling warning light come on yesterday, upon looking it was below min in the reservoir. But there was also a lot of brown scum in the reservoir. He put some water in which enabled him to drive home from work , but is obviously worried about what caused the loss and what is causing the brown scum? The car was only serviced 2 or 3 months ago and had the timing belt and water pump replaced , could any of that be involved? He rang a mate who is a mechanic who said it might be the ERG valve , or head gasket ?
Any suggestions please ?

What's the colour of the coolant?

Who did the belt and pump change?

Some floating stuff on in the bottle isn't completely unusual.

Don't go writing off the head gasket or anything else just yet for that matter, before you investigate it.

The level in my Polo drops once in a while. I am blaming a minor leak in the radiator and just top it up when the warning comes up.

[Lucas_R]

Could just be that the mechanic didn't fill up the reservoir quite enough after the water pump was replaced. Go and get some VW spec pink coolant (Nulon make one that you can buy at Repco/Supercheap etc) and top it up and just keep and eye on it over the next few weeks.

Otherwise your new water pump could be leaking.

[George II]

Yes it's got the pink fluid the in it. But it's the brown scum that's the concern. Just spoke to the service manager at vw in our town (not where my son is) and he said he thinks it is the oil cooler that is leaking, he said changing it out wasn't a big job, but flushing out the cooling system was time consuming.

The cooling was topped up ok after the service , checked. Done at the dealer in Darwin!

So he will probably be taking it back in there to get this sorted, just good to get a few ideas as to the problem beforehand the so called experts wade in wanting to replace half the engine at exorbitant rates.