Odd coolant issue

Hi everyone.

I want to first apologize if this thread is not where it should be. I'm having an issue with my Mk6 GTI that I got just two or three weeks ago. I bought the car off an auction and had it shipped to my country. After all due paperwork I've only been driving it for the past two weeks and have barely drove around 800 miles on it. Car currently has 90,500 miles and is completely stock.

Now the problem goes as follows: yesterday I got the Stop check coolant message. I pulled over and noticed my expansion tank was almost completely dry. Poured some coolant mix onto the reservoir after letting the car cool down for 40 min or so and drove off. Not even 10 min later I get the same message again and when I checked the reservoir was empty again. I had a class to go to so the car was parked for almost 2hrs. After that I poured some more coolant in and headed home (roughly 5 miles away) and when i got here the reservoir was dry. Upon inspection I noticed my water pump had a minor leak so I thought great I'll have to replace my pump. Didn't use the car for the rest of the day.

However, this mornIng I checked and my expansion tank was completely full. What the hell? Where did that coolant come from? I decide to turn the car on to see what happens to that coolant with the engine on.

For as long as the car is warming up coolant level is normal (guessing because the thermostat is closed). However, once the engine reaches normal operating temperature (190°) I noticed coolant began to be pulled from the reservoir quite rapidly. As this happened my engine temperature dropped a about half just as the Check coolant message popped up again and the reservoir became dry again. The radiator fan didn't turn on at any point. No leaks at this point since I shut it off immediately.

So I'm not sure what is happening here. Could air be trapped inside the system? I didn't mess with anything in the system in the days prior so I don't see how this could happen. Also, shouldn't the radiator fan turn on once the engine reaches operating temperature?

I tried to "bleed" the system by removing the cap, turning the car on and pressing on the rad hose that attaches right behind the throttle body. For a min it seemed to work as there were burping sounds coming out the expansion tank and some coolant showed up. But is soon stopped and the coolant was sucked back in.

Any help would be appreciated. Remember this is a salvage car so dealership is not an option.

Water pump, just changed mine, it only leaked once the thermostat opened, the pump was infact ok as it was just the seal leaking but I changed it all anyway, been fine since then.


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I took it off last night. Can't see any possible leaking spots though. How did yours look like? Mine is a BB and I think it had already been replaced as some harnesses where loose under my intake and the bracket with the triple square bolt was missing so some work had to be done there before me.

The harness under my IM was also loose and has been since I've had the car but my water pump was original going by the date on it so maybe they're all loose like that! You say you had a water pump leak but then say you can't see any leak spots? My mechanic tells me mine was slightly corroded on the engine block where the seal sits causing it to leak at the top of the square hole I think! I'll take a couple of shots of the pump seals later as I still have it in my workshop.


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Of course, not trying to worry you but have you looked for symptoms of head gasket issues such as creamy oil and sweet smelling exhaust?


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Carlosfandango said:

The harness under my IM was also loose and has been since I've had the car but my water pump was original going by the date on it so maybe they're all loose like that! You say you had a water pump leak but then say you can't see any leak spots? My mechanic tells me mine was slightly corroded on the engine block where the seal sits causing it to leak at the top of the square hole I think! I'll take a couple of shots of the pump seals later as I still have it in my workshop.


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Thanks man I appreciate that if you could. What I mean is that I thought my gasket was going to be either torn or at least swollen like some pictures I've seen. I made a mess when I removed the pump so I can't tell if there were any stains on the block until it dries up again

And no I haven noticed any oil leaks coming from my head gasket. And no weird smelling exhaust either

Here's some pics of my pump, mine was leaking at the seal on the square hole by the locating pin hole, to me it looks like yours may have some corrosion and signs of leaking between the round hole and sensor next to where the seal curves around the bolt hole with the locating pin hole next to it??


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There's also signs of oil at the same location on the block (next to locating pin) which is known to damage the seal.


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Yeah that's true. Yours was way more corroded though. Did you replace it immediately after your leak began? I mean compared to yours I think mine shouldn't even be leaking lol

raulmk6 said:

Yeah that's true. Yours was way more corroded though. Did you replace it immediately after your leak began? I mean compared to yours I think mine shouldn't even be leaking lol

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No, not immediately, I think it must have been leaking for a while and was picked up by my mechanic at its last service, I monitored the coolant level for a few weeks after that as well, it was rising and falling like yours, I wasn't having to add much at a time but it started needing topping up every day so I got it changed,

Check out this video, very informative!
https://youtu.be/_DDb7ZQ0tlE
He mentions how the oil affects the seal without being obviously damaged.


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Also mine was on the car from new going by the date on it, yours appears to be made in may 2014 which you would hope would still be ok, but I can't read the date very easily on your pics.


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Carlosfandango said:

Also mine was on the car from new going by the date on it, yours appears to be made in may 2014 which you would hope would still be ok, but I can't read the date very easily on your pics.


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Yep, mine was manufactured May 2014. I'd hope it would last longer than 2 years but oh well.

Hey do you know what differences exist between the CCTA and CBFA water pumps? I was about to buy one yesterday but noticed there where differences compared to mine. Essentially the water pump bracket that bolts onto the housing on the CCTA (BA revision) I was being offered was a bit longer than mine on the CBFA. Also, CBFA has an extra plug on the Thermostat housing that the CCTA lacks but that didn't worry me as I could easily swap mine in. It's that size on the bracket that worries me.

I was looking at ECS page and they do sell only the water pump but it doesn't mention if it's meant for CCTA of CBFA unless you're looking at the complete housing.

This is Water pump only and it's got the same part number as the pump I saw yesterday.
https://www.ecstuning.com/b-geba-parts/water-pump/06h121026ba~gba/

So if they are the same except for the connector on the Thermostat I'll buy locally. Otherwise I think I'm going to buy the complete housing off ECS.

I don't know the difference with those, I'm in the UK, my engine is CCZB which I think is basically the same as CCTA but not sure on that! Just get the parts place you get it from to reference your cars Chassis/VIN number when you order to ensure its correct!


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Or go to your local VW dealer and get a price for the pump which will give you the correct part number.


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