Coolant Leak: Connection to Combustion Chamber?

Hello everyone,

Vehicle 123d, manufactured in 2007; mileage approximately 85,000 km.

Im 1er forum http://www.1erforum.de/bmw-123d/kuehlwasser-probleme-13797-41.html sind zahlreiche Motorkrepierer dieses Motors und Baujahrs dokumentiert. Alle starben wohl den Hitzetod durch Rückstauwärme vor den Turboladern, die zu Haarrissen im Block, regelmäßig zwischen 2. u. 3. Zylled.

I now also notice coolant loss. The leak is coming from the expansion tank.

Here's what I recently tested. Please let me know if my assessments are correct and provide an overall evaluation of the case.

The coolant hose is still under pressure in the morning after it has cooled down, approximately like a poorly inflated bicycle tire.

I refilled the water cold (water temperature 18°) to Max .

I was on the train and logging data. This included full-throttle runs, slow-speed operation, and acceleration tests.

I found it amazing that at full throttle (speedometer 240, no more), the coolant temperature drops to a good 80°. I didn't think that the airflow would compensate for the engine heat. Around 100 km/h, it's 95 to 100° water temperature.

The temperature increases, especially when repeatedly accelerating in the higher gears, from approximately 1500 RPM to approximately 3500 RPM, and then, after decoupling (the water pump then hardly runs), strong braking and subsequent acceleration significantly increases the temperature, up to 108° water. With this, I was also able to reproduce the expulsion of water from the expansion tank. Under full load, it didn't expel anything.

It's also logical that the highest combustion pressure occurs approximately at the torque maximum. The highest heat is also approximately at that point. This seems to be the exact point where the gas transfer into the coolant happens.

I can assume that a coolant leak is not normal even at 108° water temperature, right? After all, in the summer, the water temperature should probably be a few degrees higher, or (the outside temperature during the test was about 5°)? Together with the still-hard coolant hose the next morning, a connection between the combustion chamber and the cooling channel is likely, right?

Quote:

Along with the still-hard cooling hose from the next morning, there's probably a connection between the combustion chamber and the cooling channel, right?

It seems so. Please also check if pressure builds up again under load with a warm engine (release the pressure while warm), even if the temperatures remain constant.

Is a water temperature of 108°F normal for this type of vehicle?
Given the current outside temperatures and normal operation, it should be in the range of 87° to 95° Celsius, or is BMW setting the coolant temperature regulation differently?
Are there bubbles in the coolant?
hg
Herbert.

It's likely due to air or an air bubble that is significantly disrupting the coolant flow, which could cause some areas to remain uncooled.
At high speeds, the engine may be forced to flow -- the temperature decreases .

If you're unlucky, you might also get some free cavitation damage.

The remaining residual pressure speaks for itself.

In BMWs, specifically the E39 M62TU engine, the thermostat is dynamically controlled. This means it adjusts its operation based on engine load; it opens earlier at full load compared to partial load. This explains why your temperature might decrease at high speed. If you are definitely losing water, it indicates a blown head gasket or a leak in the cooling system.

Best regards.
Christian.
When replacing the oil filter on my M62TU engine, they should also include a cooler.

Hello again,

Thank you for the interim responses!

Autoservice wrote:

Please check if pressure builds up again under load with a warm engine (release pressure while warm), even with consistent temperatures.

Yes, I still need to do that occasionally. I believe user BM also gave that tip in a different case before.

Herbert wrote:

Is a water temperature of 108° normal for this type of vehicle? Given the current outside temperatures and normal operation, it should be in the range of 87° to 95° Celsius, or is BMW setting the coolant temperature regulation differently? Are there bubbles in the coolant? hg Herbert

Well, I'm not sure, but does repeatedly accelerating in a high gear and then braking without using the clutch (i.e., without engaging the clutch) about 3 times still count as normal operation?

chris11 wrote:

In BMW, at least with the E39 M62TU engine, the thermostat is dynamically regulated. This means it adjusts more quickly at full load than at partial load. This explains, for example, why your temperature drops at maximum speed. The head gasket is blown or the cooling system has a leak if you are definitely losing water.

Okay, interesting. Apparently, I'm losing water exclusively through the valve in the expansion tank. I've read that it's not uncommon for (hairline) cracks in the engine block to initially only open in one direction, => initially only from the combustion chamber to the cooling system due to the much higher pressure. I haven't experienced any white smoke, difficulty starting, or anything like that yet.

Best regards,

Okay, please provide the German text you would like me to translate.

Quote:

Aha, interesting. Apparently, I am losing water exclusively through the valve in the expansion tank. I have read that it is not uncommon for (hairline) cracks in the engine block to initially only open in one direction. => Due to the significantly higher pressure in the combustion chamber, they initially only leak from there to the cooling system. I haven't experienced any white smoke, difficulty starting, or anything similar yet.

Unfortunately, the same applies to a defective metal head gasket.

Quote:

They all likely died of heatstroke due to back pressure heat in front of the turbochargers, which led to hairline cracks in the block, regularly occurring between the 2nd and 3rd cylinders.

Ist das fundamental belegt? Oder evt. Folgeschaden durch Überhitzung wegen def. ZKD?

If the ZK (certificate) is to be revoked, the ZKD (certificate authority) must carefully review the matter before any evidence is erased.

Autoservice wrote:

Quote: Aha, interesting. Apparently, I am losing water exclusively through the valve in the expansion tank. I have read that it is not uncommon for (hairline) cracks in the engine block to initially only open in one direction. => Due to the significantly higher pressure in the combustion chamber, they initially only leak from there to the cooling system. I haven't experienced white smoke, difficulty starting, or anything similar yet. Unfortunately, the same applies to a defective metal head gasket. Quote: They all likely died of heatstroke due to back pressure heat in front of the turbochargers, which led to hairline cracks in the block, regularly occurring between the 2nd and 3rd cylinders. Ist das fundamental belegt? Oder evt. Folgeschaden durch Überhitzung wegen def. ZKD? Should the cylinder head

be removed, the ZKD (cylinder head gasket) must be checked very carefully before any traces are erased. http://www.1erforum.de/bmw-123d/kuehlmittelverlust-53207-3.html#post1011007 The work instruction from BMW apparently states: "Remove the cylinder head and inspect the webs between cylinders 2 and 3 for leaks." (see }, where user "einermeiner" provides information).

Well, BMW has replaced numerous engines due to hairline cracks in the engine block, and since approximately June 2008, they have made changes to the cylinder head (improved cooling channels) and to the water-cooled EGR system.

Is it generally true, as I suggest, that gas leakage is most likely to occur at the point of maximum combustion pressure? So far, in the "1er Forum," there has been speculation that overheating occurs at full load on the highway, but my logged data does not support this. The water temperature is definitely at its lowest (around 80°C) in that situation.

Thank you in advance.

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

"LG" is an abbreviation for "Liebe Grüße," which means "Best regards" or "Best wishes" in English.

Let's put the "theory" aside. The fact is, the engine is leaking coolant from the expansion tank and is getting significantly too hot in certain load ranges. Normally, the thermostat regulates this, and the fans limit the temperature.
The expansion tank needs to be ? when being emptied.
You haven't answered yet whether bubbles will be produced in the process.
Besides a faulty thermostat or a problem with the temperature sensor, a simple possibility is that there's an air bubble in the cooling system, possibly originating from a previous repair. Was it perhaps not properly bled?
Besides a possible bleeding procedure, I wouldn't continue searching any further. If the problem is related to the cylinder head gasket, further driving will damage the cylinder head.
hg
Herbert.

chris11 wrote:

In BMW, at least with the M62TU engine in the E39 M6, the thermostat is dynamically regulated. This means it adjusts more quickly at full load than at partial load. This explains, for example, why your temperature drops at maximum speed. The head gasket is blown or the cooling system has a leak if you are definitely losing water.

According to the BMW manual, the N47S engine in the 123d definitely does not have a map cooling system, unlike the M52TU, M54, and M62TU engines.
He has a standard thermostat with a set temperature of 88°C.
The measured, high temperatures (108°C) are certainly not normal, and neither are the 80°C.
BMW is also known for the water pump's plastic impellers, which are prone to degradation.
Possibly, fins have broken off and are preventing the thermostat from functioning correctly.
Just a guess, as I've already found degraded plastic parts from the cooling system in my old E39. Also, the plastic tabs that the thermostat rests on broke off. As a result, the thermostat wasn't opening fully.
The water pump is relatively easy to disassemble on the 2.0L BMW diesel engine, so take a look and see if everything is still in good condition. The thermostat is also integrated into the water pump.
Let's do it all at once.


Best regards, Mpire.

Hello!

Yes, I've also been thinking about the water pump.

Furthermore, it should be checked whether the engine and radiator are properly bled.
I've already had one case.
where I (fortunately found it in time, before any major actions were taken),
The thin hose connecting the top of the radiator to the expansion tank was kinked/blocked.
There were similar problems before, but it was a different type of BMW.

And, just a few more thoughts I have on the matter:

You can use a pyrometer to accurately measure the actual coolant temperature on a rubber or plastic part, and thus determine if the display is malfunctioning.

Und weiterhin sollte es doch noch diese Sache mit den chem. Provide proof.
whether CO2 is dissolved in the cooling water.
as proof of whether exhaust gases are actually entering the cooling system.

In my opinion, that would still be a worthwhile recommendation.
before disassembling the engine.

Herbert wrote:

The fact is, the engine is leaking coolant from the expansion tank and is getting significantly too hot in certain load ranges. Normally, this is regulated by the thermostat and limited by the fans. The balancing tank is likely to be ?

when being squeezed.

Yes, he is.

Herbert wrote:

You haven't answered yet whether bubbles will be produced in the process.

I think it's great (see the video, especially the beautiful geyser at the end!).

Herbert wrote:

im Thema Hochladen, da Thema sonst nach Wegfall des Links sinnlos, Danke!Bitte gib mir den deutschen Text, den du übersetzt haben möchtest. The engine temperature was approximately 95-98° at that moment. [quote="Herbert"] Besides a faulty thermostat or a thermostat housing issue, a simple possibility is that there is an air bubble in the cooling system, which may have originated from a previous repair. Perhaps it wasn't properly bled?

Shouldn't it have bled itself of air long ago after driving a few hundred kilometers on the highway?

Herbert wrote:

Besides a possible bleeding procedure, I wouldn't continue searching for the cause any longer. If it's due to a problem with the cylinder head gasket, further driving will damage the cylinder head. hg Herbert

I assume the cylinder head/block is warped, assuming the same problem exists as with many older 123d models up to 06/2008 (see above).

By the way: After the initial hot start, the pressure in the coolant hose builds up again almost immediately after driving a few kilometers.

By the way: After the hot opening, the pressure in the coolant hose builds up again almost immediately after driving a few kilometers.

That's already proof that the overpressure isn't coming from the expanding coolant.
Excessive pressure is now coming from the exhaust gases of the combustion chambers (cylinder head gasket or cylinder head ).

Hello,

"The 'interruptions' in the coolant stream within the expansion tank strongly suggest a defective head gasket or a crack in the cylinder head."
The "interruptions" are actually bubbles of combustion gases (exhaust gases).

Please upload videos/images directly to the thread, as links tend to become inactive after a short time, making the thread useless.

Best regards, Rainer.

Turn off the engine and simultaneously film the expansion tank.

dieselschrauber wrote:

Hello, The "interruptions" in the coolant stream in the expansion tank strongly suggest a defective head gasket or a crack in the cylinder head.

Yes, I had also thought that .
Is it insignificant for this test that the engine was idling and the water temperature was near 100°?

dieselschrauber wrote:

Please upload videos/images directly to the thread, as links tend to become inactive after a short time, making the thread useless. Best regards, Rainer

OK, sorry, I will do that. I wasn't sure and wanted to help save server space:oops:.

Autoservice wrote:

It seems that's the case. Please check if pressure builds up again under load with a warm engine (release the pressure while warm), even if the temperatures remain constant.

Yes, the pressure is building up again.

I think I understand what that's supposed to mean: For example:
Initial temperature Water 20°
The engine is heated to approximately 95° => Pressure increases because water expands when heated.
The system cools down to the initial value 20°, => the pressure returns to the initial value again because the density of the water increases again due to the cooling.
Inside the hose, there should be no pressure anymore.

If, for example, a system that is 95°C is opened, the pressure will escape. If the system temperature does not increase further, then, based on what has just been said, a new pressure should generally not build up. If it does, it comes from the outside (combustion pressure due to a blown head gasket / crack in the block / cylinder head).

"Silly question, wouldn't you also expect further pressure build-up even in a functioning system? Doesn't new pressure form through }evaporation }? Or does that only become significant when the mixture is boiling?"

And what about the "Geysir" at the end of the video, where all that stuff briefly rises and then falls?

Thank you in advance.

Best regards,

Okay, please provide the German text you would like me to translate.