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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKVII-Mk7 Golf family including Golf Wagon (~ 2015 +)

VW MKVII-Mk7 Golf family including Golf Wagon (~ 2015 +) Discussions area for the Mk7 (2015+) Golf and Golf Wagon TDIs based on the MQB (Modularer Querbaukasten) platform.

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Old November 16th, 2017, 22:01   #1
Join Date: Nov 2017
Location: Adelaide, Australia
Default Coolant blown out from expansion bottle

Hi all, decided to share my pain with VW community after ~8 months of troubleshooting by VW (Australia). 2013 Mk7 Golf 110TDI is pushing coolant out from the surge tank. Looks like gases enter the jacket under load, accumulate and then rush up to expansion bottled causing it to overflow - overflow pipe is tiny and most of coolant is blow out through the cap threads and sprays around under the bonnet. Done so far to no effect by VW: replaced water pump, multiple cooling circuit pressure tests, replaced expansion bottle, replaced cylinder head c/w gaskets etc., replaced EGR cooler, replaced intercooler, performed engine compression test, replaced some weeping rubber hose. Any idea is appreciated. Love the car but got quite frustrated by now. Few more points: never ever had overheating or gauge temperature moving beyond 90degC; following each "blow out" can clearly hear "hissing" noise coming from the heater core suggesting pockets of gas travelling through the system.
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Old November 17th, 2017, 09:18   #2
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Join Date: Nov 2003
Location: Richmond, BC, Canada

They've replaced everything I would have suggested.

Aside from parts that have already been replaced, I can think of no other parts of the engine in which pressurized intake or combustion gasses may be forced into the cooling system, except for the engine block.

So, they just need to pop a new engine in there and you should be fine.
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Old November 18th, 2017, 15:26   #3
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Join Date: Jul 2007
Location: PNA

It sure sounds like they were just randomly replacing perfectly good parts.

I had a similar problem with a Chevy Cavalier we had bought new which was that it slowly leaked coolant somewhere. Because of actual leaks I found I replaced the radiator, heater core and water pump. The car still leaked coolant with no visual signs of leaks.

I was at the Chevy dealers parts counter and explained my problem to the parts guy and he said, I know just what you need and came back with this: https://www.ebay.com/i/322619188336?chn=ps&dispctrl=1 Apparently, GM cannot build a leak free engine and so instead they put it in all of their new cars prior to delivery.

Well, actually, the stuff works pretty well and does not plug the heater core like most stop leak products do. If you try it, just don't tell the dealer..................
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Old December 6th, 2017, 05:02   #4
Join Date: Dec 2017
Location: Spain
TDI(s): 2.0 184

Hello, I have a seat Leon 184 and I have the same problem and we are several more affected in Spain. I have replaced the thermostat and the electric pump of the heating circuit. nothing has solved the problem.
I will try to change the other electric pump.
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Old December 6th, 2017, 09:41   #5
Sad Panda
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Join Date: Sep 2015
Location: Pingree Grove IL

Did they by chance test the relief pressure of the cap?
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Old January 31st, 2018, 18:51   #6
Join Date: Nov 2017
Location: Adelaide, Australia
Default Update

Thanks to all for support. Car was with VW for more than a month, got it back and...bang, coolant is out from expansion bottle and heater stopped working (could hear hammering behind infotainment panel). Back with VW - they say heater matrix partially blocked and that is causing troubles I have. I don't understand mechanics behind it though. I still believe combustion gas breaks through somewhere, that can't be detected by pressure test or CO/CO2 tester. Any thoughts? Thanks!
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Old January 31st, 2018, 19:01   #7
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Join Date: Nov 2014
Location: maine

The mk7's have a pretty complex cooling circuit/s. There are cheap litmus type test kits that test for combustion by products in the coolant. Though, I think it would be pretty apparent visually. I'd just let them replace the heater core if it's covered by the warranty.
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Old January 31st, 2018, 22:26   #8
Join Date: Nov 2017
Location: Adelaide, Australia

Thanks Turbobrick. That is what they are busy doing right now - will update the community with results.
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Old February 7th, 2018, 19:23   #9
Join Date: Feb 2018
Location: Slovenia

I have exactly the same problem for over a year now.
I have for a fact got a bit deeper into symptoms...

It happens only when car is doing active DPF regeneration and at the same time driving on a highway with medium speeds (100-110 kph).
It never overflowed if it was pushed hard on a mountain pass road (120°C+ oil temp) - I excluded head gasket. I allways get a alarm next morning when I come home from a long trip on a highway. Although when it's doing regeneration in normal urban speeds it never overflows.

I had car at a VW dealer and they said there was a too agresive coolant (!?) inside, so they cleaned it, replace it with fresh G13 and bleed, but after 6 months problem was back.
Maybe it was the result of good bleeding it lasted so long.
Previously I had expansion tank and cap replaced also.

So I have few ideas (when doing dpf regen):
1. the cooling fan doesn't turn on at the right time (if braking from 130 to under 100kph on highway) - causing it to boil somewhere in system.
2. something to do with thermostate and therefore failing to cool it sufficiently during highway regen.
3. most recently figured out I might have a clogged cabin heater, since sometimes cabin doesn't get warm for an hour or so, but sometimes works fine (could even be air in heater element?) - I haven't found reasonable connection with the problem yet.
4. some sensor is giving false readouts about coolant temperature (dashboard gauge never go over 90°C) and causing it to boil somewhere.

Does your coolant look "rusty"? I read somewhere that is the sign of overheated coolant and that sediment can cause cabin heater to clog.

Greetings from Slovenia!
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Old June 28th, 2018, 11:03   #10
Join Date: Feb 2018
Location: Slovenia

have you figured this out yet?

I had a small overflow again today. When I heard my car was in active regen (fan runing, idle rpm@1100), I drove around a bit in order to let it finish.

When I noticed the RPMs dropped to normal (finished regeneration) I stopped and went out, popped the hood to check if there is any spill - none. When I was closing the lid I heard the fan stopped (or went to lower power - below hearing it when engine is running). Then I drove away and heard like air going trough pipes under dashboard or in front of firewall / below the windshield.
I went out and checked coolant again - and there it was - fog coming out of overflow tube and liquid around expansion bottle.
My guess is that those overflows happen right after regeneration while engine is still hot, but cooling system turns back to normal and it boils somewhere in circuit. The gauge on dashboard stayed perfectly on 90 degree as usually.

If anyone have some ideas, please help!
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Old October 17th, 2018, 09:11   #11
Join Date: Sep 2018
Location: England
TDI(s): 2.0tdi 184

Has anyone had any luck in solving this issue yet?
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Old October 18th, 2018, 05:58   #12
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Join Date: Aug 2009
Location: NH

I wonder if you're noticing clogged heater cores and the excessive temps of egr is boiling the coolant and is being pushed out.
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Old November 15th, 2018, 12:55   #13
Join Date: Nov 2018
Location: Melbourne

Has anyone had any luck with this issue I have the exact issue and VW can’t find the cause. I have replaced the water pump, surge tank and some hoses.
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Old November 26th, 2018, 05:07   #14
Join Date: Feb 2018
Location: Slovenia

I'm also thinking of partialy clogged heatercore - after the regeneration is finished, the EGR opens and hot air from DPF blows trough EGR cooler, where it boils because water is not circulating fast enough trough heater matrix.

Didn't change it yet, because VW dealership said its at least 2k eur for repair.

Does anyone know if you can get heater core out without removing entire dashboard?
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Old February 10th, 2019, 23:45   #15
Join Date: Feb 2019
Location: australia

Hi guys,
i have very same problem with my VW Golf VII 2.0TDI (2013),
just replaced Coolant Tank+Cap, water pump+gasket..we also did some pressure tests (results: negative)..but the coolant keeps overflowing through Tank Cap and sprays under coolant tank. But i gotta say, it doesn't happen after every drive..
For example:
I topped up the coolant after replacing water pump, have done 400km, looked perfectly fine, thought for a second that the problem had been solved, but did 1 more trip, and here it comes again..coolant overflows again...
Next step, at least what mechanic told me, is Head gasket...
Have you guys got some ideas?
I am really getting frustrated, because nobody has figured out what is causing the problem so far..otherwise, the car is brilliant, done 115,00kms..never had any issues...
Any advice?
thanks, Mario
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