Tighten Cylinder Head Bolts?

Hello.

Here's the translation:

'I'm having the following problem with my ALH engine. When the engine is cold, the...'
The cooling system is still under pressure. You can hear it when you open the cap. It's probably the head gasket, isn't it?

The coolant is clean and doesn't smell like exhaust fumes. The water consumption is hardly noticeable. I had water up to the maximum level 4,000 km ago. Now it's exactly in the middle between the maximum and minimum marks, which is probably about 200-300 ml.

I found a thread discussing ZKS adjustments. Should I try that? If so, how should I proceed, and how much should I adjust? Will this fix the problem completely, or will it reappear after a while?


Regards,

Paul.

Hello.


My suggestion.
Continue driving and observe.
I wouldn't overemphasize the pressure in the cooling system when the engine is cold. Instead, I would pay more attention to the water consumption.

I wouldn't recommend tightening the cylinder head bolts. It's best to first check if there's any leakage in the cooling system, such as at the water pump, radiator, and all hose connections, etc.
Also, maybe check the heat exchanger in the vehicle (heating system).

With such a small amount of water loss, you can initially rule out the head gasket for now.

Best regards, Charly.

"Sometimes, just try swapping the gasket; it won't cost you 10 euros. If the head gasket is faulty, it should actually leak under full load, which is what you observed."

The water consumption is already too high. Let's check to see if it's leaking somewhere.

Yes, there are signs of coolant leakage around the container. So, should I immediately shut everything down, or should I just change the lid and see what happens?

I'll check (or have someone check) to see if you have exhaust gases in the cooling system. Then you can check what the actual temperature reaches (using VAG-COM, not the instrument cluster). You don't want a stuck thermostat that's causing the engine to run right at the boiling point. Also, the water pump should be okay; is it leaking into the reservoir?

Do not rush to remove the cylinder head. As a last resort, try tightening the cylinder head bolts slightly. If that helps, then proceed with replacing the cylinder head gasket. In one case, someone tightened the bolts and it prevented further damage to the cylinder head (the gasket had "eaten" into the head).

Okay, I'll help you with the process.

What I have available is a VAG-COM device, a Type-K thermocouple in the inlet line to the heater core. And I can also install a pressure tap instead of the Type-K thermocouple, where I can measure the pressure from the cooling system using a digital pressure gauge.

I'm going to warm up the engine now and then take a lap with full throttle. I'll let you know what the water temperature is.

EDIT: The water temperature did not exceed 95°C, and both radiator hoses were hot. I could see new water leaks around the container. When I opened the container, I observed something like gas. There were many small bubbles, similar to those in a carbonated drink bottle. I closed the lid again. When the engine is cold, I usually have a vacuum in the system, or am I mistaken?

Hi,

If you see traces of coolant around the container, check the hoses there to make sure they are properly connected and replace the cap! After that, you can still perform actions like "measure the CO2 content in the coolant" or "remove the cylinder head."

Regards,
Sure, here is the translation of the text from German to English:

"Micha"

Quote:

When the engine is cold, the cooling system still has pressure on it. You can hear it when you open the cap. Could it be the head gasket?

In my opinion, all the symptoms unfortunately point to a defective head gasket. It could also potentially be a faulty thermostat. In any case, the residual pressure of the coolant when the engine is cold is not normal and a clear indication of combustion gases entering the cooling system.

When the engine is cold again, I usually have to have vacuum in the system, or am I mistaken?

Not necessarily. The lid has a valve that opens under vacuum, but also allows a certain amount of overpressure (which raises the boiling point), after which it also opens.

Regards,
0588.778

Okay, I've now measured the pressure in the cooling system. While driving at full throttle, it's approximately 1.2-1.3 bar. In normal operation, it's 0.8-1.0 bar. With a cold engine (3°C), I'm getting 0.3-0.4 bar of overpressure in the cooling system.

What do you think about the values? I have to drive about 15,000 km non-stop in my car in a month. Should I just ignore the warning lights or buy spare parts and take them with me?

'Valve in, valve out. For me, this is physics. If I heat water in a closed container, the container is under pressure. If I cool it down again, the pressure is zero. And a cooling system is, for me, a closed container. If the valve opens due to excessive pressure, then the system should have a vacuum when it's cold. If you consistently had overpressure in the cold state without any water loss, it would be a perpetual motion machine.'

Quote:

Valve in, valve out. For me, that's physics. When I heat water in a closed container, the container is under pressure. If I cool it down again, the pressure is = 0. And a cooling system, for me, is a closed container.

That's exactly how it is, and no other way. Nevertheless, 0588.778 is correct that no vacuum is created when the water cools down, because almost all cooling systems are open to the inside through a valve.

There are also semi-open cooling systems (often used by Japanese manufacturers) that are filled to the brim, and where excess water is directed through a pressure relief valve into an external, open container. During the cooling phase, the cooling water flows back into the cooling system due to the pressure difference.

Quote:

What do you think about the values? I have to drive about 15,000 km non-stop in my car in a month. Should I just ignore the warning signs or buy spare parts and take them with me?

The 95 degrees Celsius is 10 degrees too high for the normal operation of my system.
It's a shame you didn't release the coolant pressure after it reached operating temperature to check if it would rise back to the maximum pressure under load without an increase in temperature. If you had done that, the problem would have been almost 100% certain to be identified.

I would immediately open it (if it's defective).

'@BM: I haven't removed the pressure gauge yet, so I can continue testing. What should I do? Should I run the engine at idle with the heater on, keeping the temperature below 90°C, and then open the reservoir cap when it reaches 90°C, close it again, and see if the pressure increases while the water temperature remains constant?'

The engine reached 95°C at full throttle, and I pushed it to its limit for 10 km. I alternated between accelerating from 60 km/h to 140 km/h, braking, and then accelerating again, etc. I didn't log the water temperature during normal driving. And that great 'egg timer' in the combination instrument always shows 90°, no matter what you do.

Quote:

@BM: I haven't removed the pressure indicator yet, so I can continue testing. What should I do? Should I run the engine at idle, with the heater on, so that the temperature doesn't rise above 90°C, and then open the container when it reaches 90°C, close it again, and see if the pressure increases again, while the water temperature remains constant?

Okay, it's important that it has reached its operating temperature so that the natural expansion of the coolant can occur. I would first warm it up normally, release the pressure, then run it at full load for a while, making sure that the temperature doesn't rise too much.

The rest is physics. With my AJM model, it used to be that under full load, it would empty the entire fuel tank within 10 kilometers on the highway.
What is your water loss like?

Approximately 200-300 ml per 4 kg of body weight.

Okay, so I warmed up the engine normally today. I opened the cover in the parking lot. The water level in the container rose by about 1 cm. I drove 10 km at 160 km/h. I closed the cover. The water level was exactly the same as it was after opening the container. Then I drove another 10 km at 200 km/h (full throttle). The cover was closed, and the water level didn't change. The pressure in the system was back to 1.2 bar at full throttle and about 0.8 bar at idle, which is the same as it was before opening the container. However, the water level didn't drop.

Quote:

The pressure in the system was back to 1.2 bar at full throttle and approximately 0.8 bar at idle, which is the same as it was before opening the container.

So, 0.8 bar, not 1.2 bar. Because those pressures are generated by the water pump's output.

It's also possible that the coolant is reaching its boiling point in certain areas, which is why the pressure builds up repeatedly. Normally, these engines don't exceed 90 degrees Celsius even under load, at least from what I've seen so far, or has the car been modified with a chip? However, the residual pressure (when the engine is cold) still suggests a faulty head gasket or a warped cylinder head.