[Tom '74 911]

Hello!

I do lots (almost all) of the work on my old air-cooled Porsches, but only very minimal work (almost none) on my newer or water-cooled cars so I am not wise to the ways of the water-cooled coolant system, at least in actual practice.

I have a 2016 VW Golf R that I love. Last June I noticed oil in the coolant reservoir and took it to a VW dealer (gasp, I know) for diagnosis and service. They ended up replacing the oil cooler, thermostat, all related gaskets etc..., filled the cooling system and did an oil change. Apparently and unfortunately, I think this is a common problem/thing with these cars.

When I got it back from the service, the coolant in the reservoir looked clean (the reservoir was also replaced). Now 6 months later, I just refilled the windshield washer tank over the weekend and noticed it looked like there is oil mixed in the coolant reservoir again. Before I freak out, I'm wondering if the dealership didn't do a good enough job flushing the system and getting all the residual oil out from the previous episode and what I'm seeing is just that and not a bigger issue... I don't see anything on the repair receipt that indicates that they did any "flushing" just "replacing".

I am pretty friendly with Youtube and found some helpful videos on flushing the cooling system. Some even suggest using detergent or some other radiator flush and cleaner product.

This seems like a pretty straightforward process - am I missing anything? The trickiest part seems to me to be figuring out what container to use to collect the dirty coolant and how to dispose of it. Seeing as I imagine I'll need to flush the system multiple times, that's going to produce a lot of waste that I can't just drain down the sink. What do I do with it?

Also, I'd love to hear any tips about the process if anyone has any to share...

Thanks so much,
Tom