This is a strange one it started about 3 months ago the water level light came on the header tank was empty,

But as soon as the cap was released with a woosh the water returned to the correct level and light went out.

A new cap was tried with no change.

This now happens every day about 60 sec after start up I release the cap and tighten it again and it's no more trouble for the rest of the day even with 9hr standstill at work.

The engin runs like a clock and doing over 60 to gall.

I have been told that the head gasket is gone.

Any other ideas please plumbob.

Seeing as it's still under warranty what's your dealer said?

Seeing as it's still under warranty what's your dealer said?

I would say that that is a very possible cause and say to you PlumBob, get it too your dealer ASAP.

Don't however tell them that you have been releasing the pressure for months now as if they are w@***rs they might try and shift some of blame onto you by saying it could've been fixed if you had brought it in weeks ago!

There are other possibilities like another defective cap, so get it to your dealer for a good check up.

I would expect if the head gasket had gone that the water returning into the reservoir would show some degree of oil contamination.

The fact the water returns on release of the cap would indicate a vacuum in the cooling system, and while I'm not familiar with these type of engines would expect that the system may just need bleeding.

I've been keeping a very close eye on my coolant as I am not sure I'm not losing some. When first checked it was 3/5 up from min to max. A couple of hundred miles later it had dropped to on the minimum. I presumed an airlock had come out. Checked again after a few more miles and it was down again and only just touching the min mark, so I removed the cap to add some coolant and as I did the header tank hissed and the level came up every so slightly.  I have topped it up and in the 600 miles since I think it has not gone down ( difficult to tell at home, drive and road both slope) but it seems to go up and down a touch, and the tank hisses if I open the cap.

If it was the head gasket I would expect the coolant level would go down but not return once the cap was released.

Or there would be signs of oil/fuel contamination in the coolant.

 

My first thought would be the same as NookieBear that there is some kind of vacuum caused by an air-lock.

I'm not familiar with the VW engines but I don't think the header tank should be pressurised.

Is there an overflow outlet at the top of the tank to vent fluid if its overfilled?

 

I've seen something similar on a friends car when they used the wrong coolant type to top up & it coagulated in the system.

 

 

I'd take it straight to the dealer with the low coolant light is illuminated & ask them to fix it.

im having the same problem ,please if you take your car to dealer tell us what he says.thanks

 

I'm not familiar with the VW engines but I don't think the header tank should be pressurised.

 

It is a sealed system so the header will be at the same pressure as the rest of the system?

 

What happens if you leave the engine running from cold with the cap off until it reaches normal operating temperature? At this point the thermostats will have opened and it should help get any airlocks out of the system. You can help this by squeezing hozes by hand etc. If the level drops like this then top it up whilst warm to the correct level.

Mine does this also, it was below the min mark the other day after a long run, and then when slowly opening the cap, there was a rush of pressure releasing and it went to over the max mark, doesnt appear to follow any pattern, just seems a quirk.

 

The coolant is clean and no oil debris or skank in the header tank.

 

Not sure why it does it, my last 6 Skodas never did this....

Remember that when the system is up to temperature, pressurised that the level will be lower than when its at temperature but under no pressure. This is due to expansion and what the header/expansion tank is for. If it's low when cold put some more fluid in and if you do over fill it then it will blow it out of the overflow when it warms up.

Sounds like an airlock somewhere in there to me, take it back to the dealers when the low level comes up

Hmmm... Looked at mine considering we're off to the west country for the weekend and it was bang on the low level when stone cold, released the cap and it didn't move so, I've filled it to the upper level.  Its done 5k miles from new, its also used a litre of oil in that time and I've driven it hardish since 500 miles, I'll just keep an eye on it from now on.

It is fairly simple to diagnose a head gasket failure, they can test the coolant for contamination.

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