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Chris_J
01-08-2008, 12:16 PM
Hello all.
I have a 115 GT TDi and I'm worried about how the coolant level behaves. Previous to this car, I've had two Polos and both of them I used to top up the coolant level to MIN when the engine was cold. As the engine reached full operating temperature, it would rise to MAX until it cooled.
However, on the Golf, I suspect something may be wrong. Since I got the car a few weeks ago, the coolant level does the complete opposite. I'll top it up to MAX when cold, and when the engine is fully hot, the level will be just below minimum. Of course, my fist suspicions are that it has lost coolant, but once the car has cooled overnight, the level returns back to MAX again.
I undertstand that these systems are pressurised under normal use, but there's no way you can compress a liquid, so the level shouldn't be going down. The engine is not consuming any coolant, so I'm not suspecting headgasket just yet. There's definately no air locks in the system, as I fully bled it when doing a coolant flush and change last week. I've also replaced the cap on the expansion tank with a new one, as it wasn't holding pressure well.
Any ideas what is going on?? http://uk-mkivs.net/emoticons/emotion-7.gif

B8SON
01-08-2008, 01:59 PM
Hello all.
I have a 115 GT TDi and I'm worried about how the coolant level behaves. Previous to this car, I've had two Polos and both of them I used to top up the coolant level to MIN when the engine was cold. As the engine reached full operating temperature, it would rise to MAX until it cooled.
However, on the Golf, I suspect something may be wrong. Since I got the car a few weeks ago, the coolant level does the complete opposite. I'll top it up to MAX when cold, and when the engine is fully hot, the level will be just below minimum. Of course, my fist suspicions are that it has lost coolant, but once the car has cooled overnight, the level returns back to MAX again.
I undertstand that these systems are pressurised under normal use, but there's no way you can compress a liquid, so the level shouldn't be going down. The engine is not consuming any coolant, so I'm not suspecting headgasket just yet. There's definately no air locks in the system, as I fully bled it when doing a coolant flush and change last week. I've also replaced the cap on the expansion tank with a new one, as it wasn't holding pressure well.
Any ideas what is going on?? http://uk-mkivs.net/emoticons/emotion-7.gif

The first thing I would do is bleed the water system as it sounds like there could be air in the system. Make sure you fill it up with the correct ratio of antifreeze to water and you should be fine.

If you see any oil in the bleeded out coolent (or any white gunk in the oil if look in the rocker cover) then it could be the headgasket but I will add that the headgasket on the golfs are pretty strong.

Good luck

Chris_J
01-08-2008, 02:15 PM
Do you have any idea how to properly bleed the system? I believe there is a little bleed hole on the left-hand side pipe going into the heater matrix, but there was nothing on mine.

I did a 50/50 pre-mix of G12+ when I flushed and renewed the coolant, and it's all still nice and clean. The old stuff that came out was a bit rusty and green, but no oil residue or any unusual particles in there.

B8SON
02-08-2008, 09:11 AM
Do you have any idea how to properly bleed the system? I believe there is a little bleed hole on the left-hand side pipe going into the heater matrix, but there was nothing on mine.

I did a 50/50 pre-mix of G12+ when I flushed and renewed the coolant, and it's all still nice and clean. The old stuff that came out was a bit rusty and green, but no oil residue or any unusual particles in there.

The systems on the golfs bleed themselves. Run the engine with the cap off for a while and that should do the trick. It doesn't sound like your headgasket has gone. The level will vary between hot and cold. Just make sure it's not overheating and you'll be fine.

Chris_J
02-08-2008, 10:28 AM
I'm certainly hoping it hasn't gone anyway, as I reckon it would take me a good day or more to do the HG on these.

I'm just concerned because in the past, unusual behaviour of the coolant level has always turned out to be initial signs of HG failure. I must admit though, the cases I've seen were a little more extreme - i.e one day the level would be brimmed to the top of the expansion vessel, then the next it would be way below min, with immense amounts of pressure in the system.

Anyway, I'll let it run again for a while with the cap off. I did this when I first refilled the system, as well as massaging the pipes, but I didn't burp, so maybe there is still air trapped in there.

Thanks for your input mate.

Chris_J
06-08-2008, 11:06 AM
Okay, bled the system as described and yesterday I set the level at the fill line (i.e MIN mark) with engine cold and no pressure in the system.

Took it for a longish motorway drive last night of about 50 miles. Engine was fully up to temp with radiator nice and hot all over. Returned home and the level was a centimeter or so below the MIN line. Left it overnight and the level had dropped a little further once it had cooled. I then released the cap and after a small amount of pressure was released, it returned exactly to the level it started at.

If air was getting into the system either via pressure (headgasket leak) or via vacuum (coolant leak) then the level would drop as the coolant expanded into the air spaces, but then return to normal as the liquid cooled (almost normal if it was leaking coolant!). The fact that it remains in the low position suggests to me that there is a space in the system that can only be filled when it is under pressure.

I'm thinking heater matrix issue here?

benGT
06-08-2008, 11:49 AM
I had similiar problem and turned out to be head gasket.

Have you had it pressured tested?

Chris_J
06-08-2008, 01:09 PM
Not had it pressure tested, but I'm getting that done and a sniffer test tomorrow. Also could do with a compression test too.

I'll be suprised if it is the HG. Was yous loosing coolant as well?

benGT
07-08-2008, 02:18 PM
Yeah was loosing coolant also!

Hope for your sake its not the HG

Chris_J
07-08-2008, 10:44 PM
Had a sniffer and pressure test done today and came out clear. Looks like it's not the HG, which is very pleasing!

qqqwww
04-02-2009, 06:46 PM
Hi Chris J,

Did you ever find out what the problem was?

I have the same. Set coolant is at correct mark, replace cap. Drive. Level drops. Leave to cool, then level is low and pipes still pressurised. Open cap and level comes back to the mark.

Have changed thermostat, bottle, cap and water pump. Driven miles with the cap open too.

Going to get compression tests / sniff done.

Hoping not Head Gasket. Please say you solved your's easily!

Thank you...