VW Golf - flushing coolant system help?

[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

[wilnj]

I found these, not sure if this helps.

https://www.golfmk7.com/forums/index.php?threads/coolant-flush.388996/

https://www.vwvortex.com/threads/how-to-flush-the-coolant-mk7-gti.9350297/#post-113751195

[Arizona_928]

How much oil are you losing?
Coolant in oil?

To do the oil cooler requires one to drain the coolant.

[Tom '74 911]

Originally Posted by wilnj

I found these, not sure if this helps.

https://www.golfmk7.com/forums/index.php?threads/coolant-flush.388996/

https://www.vwvortex.com/threads/how-to-flush-the-coolant-mk7-gti.9350297/#post-113751195

Thanks for the links. I'm not plugged into either forum, but that's a great place for me to start...

Originally Posted by Arizona_928

How much oil are you losing?
Coolant in oil?

To do the oil cooler requires one to drain the coolant.

Losing essentially zero oil, not measurable on the dipstick at least. There currently is not a noticeable amount of coolant in the oil... and there wasn't when I brought it in for service 6 months ago either. During the service, the coolant was drained & replaced when the oil cooler was replaced - mentioned that in my original post.

[911 Rod]

White gunk inside the oil cap?
I'd be flushing it with water and detergent that can dissolve the oil.
But ... I've never done it before.

[Tom '74 911]

Originally Posted by 911 Rod

White gunk inside the oil cap?
I'd be flushing it with water and detergent that can dissolve the oil.
But ... I've never done it before.

Oil cap is clean.
Flushing with water and detergent is my thought too, but I've never done it before either!

[cockerpunk]

if its back, its probably the oil cooler seal again. or head gasket.

[Arizona_928]

Originally Posted by Tom '74 911

Thanks for the links. I'm not plugged into either forum, but that's a great place for me to start...



Losing essentially zero oil, not measurable on the dipstick at least. There currently is not a noticeable amount of coolant in the oil... and there wasn't when I brought it in for service 6 months ago either. During the service, the coolant was drained & replaced when the oil cooler was replaced - mentioned that in my original post.

Can you post a pic of your coolant bottle with the cap unscrewed. The red fluid that VW uses does get brown. I would pull a dram vial worth and see if you can see sediment separate or aq/organic layer form.

I would flush the system with hose water. Empty system and flush with DI water. then back up with that special vw coolant.


Used coolant (non contaiminated) can be disposed of down the drain at some water treatment plants. Ie. Phoenix. You will need to call the your water treatment plant to confirm or pay for it at the local solid waste facility. But that is just the waste coolant. It is perfectly legal to let the flush go down the drain (3% of containments is what the EPA reg allows iirc). If you really don't feel like that you can collect the flush and let the water evaporate and just throw away the solid salts that are left behind.

[GH85Carrera]

Every other spring I flush the coolant in my El Camino. Drain it out, hook up a garden hose, fill it up, and run the engine for a while to make the water pump, pump some water.

The radiator is pretty old. Just standard old Prestone green fluid. I take the old fluid to our local hazardous waster disposal facility along with the paint, brake fluid, motor oil, and florescent light bulbs I accumulate.

I have no real help for a VW system with an oil cooler. The Elky does have a transmission cooler built into the radiator, but it has never leaked. I had to upgrade the two row radiator with a 3 core radiator long long ago when I discovered the factory 2 row was just not adequate on hot days.

There are adapters that go from a garden hose to the radiator fill cap to flush it all.

[wilnj]

My recollections is that the VW engine is prone to trapping air in the cooling system, hence why the flushing instructions include raising a wheel to get water moving through that trapped section.

That may not have been done in the previous service.


Sent from my iPhone using Tapatalk

[Tom '74 911]

Originally Posted by Arizona_928

Can you post a pic of your coolant bottle with the cap unscrewed. The red fluid that VW uses does get brown. I would pull a dram vial worth and see if you can see sediment separate or aq/organic layer form.

I would flush the system with hose water. Empty system and flush with DI water. then back up with that special vw coolant.


Used coolant (non contaiminated) can be disposed of down the drain at some water treatment plants. Ie. Phoenix. You will need to call the your water treatment plant to confirm or pay for it at the local solid waste facility. But that is just the waste coolant. It is perfectly legal to let the flush go down the drain (3% of containments is what the EPA reg allows iirc). If you really don't feel like that you can collect the flush and let the water evaporate and just throw away the solid salts that are left behind.

Sorry it took so long to post some photos. We've been in the middle of a super cold snap and it's been tricky to time taking a photo etc...

I'm not sure how helpful these will be... I will try to suck a little fluid out into a clear container in the very near future and post a photo of that too. The coolant is a little brownish, which is what prompted me to start the thread. It's only 6 months old, so should look as-new. It was much pinker and cleaner looking right after the service 6 months ago.

[911 Rod]

Maybe they didn't do a full flush? Should it be green or pink? I'm thinking mixing green and pink would give you the colour you have.
I bought a Schwaben coolant refill tool for my 996 and it was a joy to use. Not only did it fill without any air voids, it pressurized and found a leak that just needed the clamp tightened.

https://www.pelicanparts.com/More_Info/PEL003466SCH01.htm?pn=PEL-003466SCH01&bc=c&SVSVSI=

[Arizona_928]

Originally Posted by 911 Rod

Maybe they didn't do a full flush? Should it be green or pink? I'm thinking mixing green and pink would give you the colour you have.
I bought a Schwaben coolant refill tool for my 996 and it was a joy to use. Not only did it fill without any air voids, it pressurized and found a leak that just needed the clamp tightened.

https://www.pelicanparts.com/More_Info/PEL003466SCH01.htm?pn=PEL-003466SCH01&bc=c&SVSVSI=

Vw coolant is pink. Not green

It looks okay to me tbh. The brown residue on the bottle could be oxidation or contamination. I would pull a sample after it's been ran through the system to confirm or see if the oil cooler work is still under warranty and go that route

[Tom '74 911]

Originally Posted by Arizona_928

Vw coolant is pink. Not green

It looks okay to me tbh. The brown residue on the bottle could be oxidation or contamination. I would pull a sample after it's been ran through the system to confirm or see if the oil cooler work is still under warranty and go that route

Yes, definitely pink, not green coolant color for this car. Thanks for your opinion. I know it doesn't look horrible, but it's just not AS clean looking as when I picked it up after the service... hence my wondering if there was much effort put into flushing the contaminated coolant out during the service. I'm hopeful that the original problem hasn't reoccured... just that the coolant is a little dirty/contaminated from what was leftover from the old coolant...

I think I'll start w/a more complete coolant flush at some point in the near future so the fluid is nice and clean again. Then I can watch it over time to see if gets contaminated looking again, which maybe indicates a bigger issue...

Thanks for all the thought and comments,
Tom

[Tom '74 911]

Had a chance to work on this yesterday and managed to do what I think is a partial flush of the coolant system. I wasn't able to find a drain plug so I pulled a low hanging radiator hose and drained it that way. The coolant was pretty dirty, but I don't have any reference for exactly what that means... I drained whatever would come out of the hose I popped off, then filled the reservoir with water a few times and let that drain through, then filled the reservoir and started the car. I let it run for a few minutes and then repeated the process. Finally, I put it all back together, filled the reservoir w/coolant and drove home. I stopped to top off the reservoir on the way home.

Unfortunately, the coolant in the reservoir looks pretty dirty again, which is what leads me to believe I was only able to drain part of the coolant in the system and the new coolant I added mixed with whatever was remaining of the old.

A quick question - is the coolant system capable of purging air on its own? One of the things I am uncertain about is that I put the same amount of coolant back into the system that I removed. Beyond keeping an eye on the reservoir and topping it off if it's low, is there anything else I can/should do?

Thanks,
Tom

[fanaudical]

My experience with VW/Audi stuff:

- The coolant does look dark to me. The Pentosin VW coolant I use stays very pink.

- The reason for the special coolant is that all the other coolants seem to eat head gaskets.

- I'd take that sample you have and just let it sit in the corner of the garage undisturbed for a week; see if there is anything floating on top after a while.

- There is usually an air purge screw somewhere in the cooling system at the high point. That said, I often find it necessary to drive a car up/down steep hills while at temp and the heater going full blast to purge all the air out of the cooling system.

[rfuerst911sc]

You said you let the car run for " a few minutes " between flushes . Did the car get hot enough for the thermostat to open ?

[Tom '74 911]

Originally Posted by fanaudical

My experience with VW/Audi stuff:

- The coolant does look dark to me. The Pentosin VW coolant I use stays very pink.

- The reason for the special coolant is that all the other coolants seem to eat head gaskets.

- I'd take that sample you have and just let it sit in the corner of the garage undisturbed for a week; see if there is anything floating on top after a while.

- There is usually an air purge screw somewhere in the cooling system at the high point. That said, I often find it necessary to drive a car up/down steep hills while at temp and the heater going full blast to purge all the air out of the cooling system.

Thanks for the comments. The sample I took is sitting in my shop; I'll see how it looks after some time...

I did read about turning on the heater to help circulate the coolant, which I forgot to do yesterday. I did keep an eye on the temp. gauge and oil temp. on the way home to make sure neither spiked too high (they didn't). I'm not convinced that the coolant temp. gauge actually works though - I've never seen it go above 200 degrees.

Originally Posted by rfuerst911sc

You said you let the car run for " a few minutes " between flushes . Did the car get hot enough for the thermostat to open ?

Excellent question. Probably not. I probably could have been more patient and through with the flushing procedure. I was kind of stumbling through my first time doing it... will be better practiced the next time!

I bought some of this stuff to help flush out any gunk. But after draining the system the first time, I decided not to use it as I wasn't certain that I'd be able to easily flush it all out. After reading the directions, it didn't seem like the kind of stuff you'd want to leave in the system for very long...

[rfuerst911sc]

FYI: the liquid laundry detergent Shout is excellent at cleaning out oil contaminated coolant systems .

[unclebilly]

Originally Posted by rfuerst911sc

FYI: the liquid laundry detergent Shout is excellent at cleaning out oil contaminated coolant systems .

What would happen if you put a tablespoon of sunlight into your coolant, went for a drive and then drained it, filled it with water, went for another drive, drained it (check out what Color the water is now), then top it up with vw coolant and called it day?

The idea is the detergent should collect the oil, the water should rinse the detergent (and oil) out, if you were worried about diluting your coolant with trapped water, you could repeat the last 2 steps again.