Cooling Water Temperature / Water Loss

Hi everyone,

'Can anyone tell me at what temperature the coolant temperature stabilizes? I have a problem with my AJM engine, manufactured in 7/99, which is losing 80 liters of coolant. Strangely, this only happens when I'm driving at high speed on the highway for an extended period. Today, I drove on the highway for about an hour, and I used VAG Com to log measurement group 7. The fourth value (which I believe is the coolant temperature) rose to 110°C. Afterwards, I had no water left in the expansion tank, and some water accumulated underneath it. At normal speeds on country roads, the value was around 85-90°C. I suspect that my thermostat is not working correctly and that my coolant is boiling over under load.'

Best regards,
Stefan

Hello,

The coolant can reach up to 110°C with aggressive driving. This is not unusual. The water circuit is a closed system, which means that overpressure can build up, and increased pressure raises the boiling point of liquids (the principle of a pressure cooker ).

In plain terms: at 110°F, the coolant should not be boiling, as long as your cooling system is leak-proof!

Either you have a leak somewhere (search for it) or the coolant reservoir cap is faulty. It contains a seal and a pressure relief valve, which tend to fail in older vehicles. Even though yours is relatively new, I would recommend replacing the cap, as it shouldn't cost much. (assuming you can't find any other leaks!)

Regards,
Private.

Hi,

In my hot water heater, the water temperature in the summer ranges between 85 and 95°C (when running at full power).

Best regards, Rainer.

Hi.

'There are no visible leaks externally - that is, the oil isn't dripping, there's no smoke, and the hoses and radiator are all sealed. The system is also building pressure, because when I open the expansion tank, there's quite a bit of pressure inside. The only puddle that forms is on the right side, under the expansion tank (after driving at a fast pace).'

Best regards,
Stefan

Oh dear, I don't want to be negative, but I experienced the same thing. The puddle on the right side of the engine is coming from the pressure relief valve of the expansion tank!
I had exactly the same symptom, and no one could help me. I repeatedly mentioned the head gasket, and tests were done, including chemical tests to see if the water was mixing, but I was told that it couldn't be the head gasket because it fit properly!
I replaced everything: the container, the lid, and the thermostat, but it's still not working!
"As soon as I added material, the water reservoir exploded and was empty! After a lot of searching and exchanging money, the expert kindly decided to remove the head. And sure enough, the material went from the combustion chamber to the water channel, and I was right the whole time! Afterwards, he said that it was quite strange that the pressure had been maintained."
Okay, I understand now. There's an insane amount of pressure involved, and if you introduce any material, it will just blow through. But of course, they only checked the pressure at idle; those idiots!
"That's where the vicious cycle begins: because air is entering from below, a steam bubble forms. This bubble pushes the liquid upwards into the expansion tank. When the pressure becomes too high, the valve releases it, and only when the steam reaches the expansion tank does the indicator light come on, which is already far too late – meaning the seal is likely to fail even more."

gruzz mozz

PS: I don't wish this on you, but the same thing happened to me!

Hi,

Head gasket or crack in the cylinder head.


Best regards,
Stefan

"110° also seems quite high to me. Once, I had a reading of just over 100° (according to the instrument), which was at Lake Garda, in August, at an altitude of about 1000 meters, using the first and second gears. First with the air conditioning on, then with the heater, and finally with the windows open..."
Never on the highway.
Or perhaps the temperature only rises when the gas from the cylinders displaces the water?

Hello,

It's hard to say exactly why, but the temperature rose after a period of fast driving. Then, the control unit displayed a message to check the coolant level. After I drove at a moderate speed to the next parking area, the temperature went back down. I then topped up the coolant, continued driving cautiously, and the temperature remained at around 85-90°C.

Best regards,
Stefan

HEAD GASKET!!

Hello,

I know all too well how difficult it is to accept: a blown head gasket!

I also spent weeks developing theories about theories, but eventually I couldn't ignore the truth anymore.

After the repair, even after driving at a fast pace, there is hardly any pressure buildup in the expansion tank, whereas before, when opening the cap, large amounts of coolant would gush out.

Regards,

Thomas Meyer.

mozz wrote:

I'm starting to understand, there are some incredibly high pressure readings there, and if you introduce material, it will blow through, but only at full load, and those idiots checked the pressure while the system was stopped! "That's where the vicious cycle begins: because air is entering from below, a steam bubble forms. This bubble pushes the liquid upwards into the expansion tank. When the pressure becomes too high, the valve releases it, and only when the steam reaches the expansion tank does the indicator light come on, which is already far too late – meaning the seal is likely to fail even more."

Hi,

I can only confirm that . Install a new head gasket .

I also have a story about this, involving my old Passat and a head gasket failure.

Due to the high volume of coolant flowing from the combustion chamber into the cooling system, after a long highway drive, the warning light for low coolant illuminated. I then stopped, opened the reservoir, and saw that it was completely empty. I then called the ADAC (German Automobile Club), they came to assist, and after some time, the reservoir was full again (a great demonstration effect ). The pressure must have been so high (the pressure valve apparently couldn't handle it) that the radiator hoses expanded and, after opening the reservoir, slowly contracted .

Hi,

I guess I'll have to bite the bullet and replace the ZKD .
I will report back once I have all the parts together and have completed the replacement.

Best regards,
Stefan

Hi Stefan,

You don't actually need to go to a dealership to get your parts: the cylinder head gasket and seals are from Elring or DPH (also used by VW) .

Hello,

I previously reported on my timing belt replacement on my A4 AFN. Here's a quick reminder of the potential pitfalls:

1) The camshaft sprocket must be removed, so have an alignment tool ready.
2) Be careful when disconnecting the vacuum hose from the EGR control valve, as the plastic nipple is prone to breaking.
3) Due to space constraints, the nut on the pressure line leading to the turbo cannot be tightened properly. If you try to loosen it, the line will shear off. It's better to loosen the line on the oil filter side instead.
4) It's better to loosen the return pipe from the turbo to the oil pan from the oil pan side. Trying to get the screws back in on the turbo side nearly drove me insane.

I don't know if these tips apply to your vehicle. But I wanted to mention them anyway.

Regards,
Thomas.

Sure, here's the translation:

"Here's another addition:"

- Get a HAZET scraper for the sealing surfaces and be especially careful around the ZK (cylinder head) due to the grooves!! However, I've heard of people who slide the cylinder head over wet sandpaper (in which case the valves need to be removed -> new valve stem seals).

- If you have the spark plugs installed, make sure that the spark plugs are not resting on anything before you remove the head (I'm not sure how it is with your setup) .

- The metal plate between the camshaft wheel and the spark plug can be annoying, so it may be worthwhile to remove it (the ESP wheel needs to be removed).

- Adjusting the valve clearance on a warm engine is certainly not necessary (-> metal head gasket)

Hi,

Thank you for the tips. I think I will tackle the issue next week.

Best regards,
Stefan