Öl im Kühlwasser | Posts 16+

Morning!

I recently had the friendly mechanic perform a cylinder head test. They simply replaced the expansion tank cap with a test cap that had two small, transparent acrylic cylinders attached to it, which were filled with a special liquid! The strange thing is that the liquid didn't change color, and no bubbles appeared, which means, according to the test, my head gasket is in good condition.

Since I was at a different workshop this time, I pointed out the oil cooler to the master mechanic there again. However, he said that only vehicles with the AAT engine, which were originally ordered with a trailer hitch or an automatic transmission, had them.

For those who are interested >> I also received an offer for a ZKD replacement: 675€ .

@ ZeroCool22

Do you know if I might have an oil cooler?

Best regards,

Andi.

Hi Andi,

Was wäre, wenn man beim Test auch voll durchgedrückt hätte?
I already had a leak in my AHF (Automatic Hydraulic Fluid system) that was only noticeable when driving at full throttle due to water consumption; at low speeds, there was almost no water consumption .
Does your engine have any coolant hoses that connect to the engine block and are sealed with an O-ring? Are the core plugs (freeze plugs) in the block sealed?

Add some UV dye to the coolant, drive around for a bit, and then shine a UV lamp on the engine compartment to check for leaks.

Best regards, Rainer.

Hello!

@Rainer

Yes. During the test, the engine was definitely revved up, but it was only idling! I can imagine that the peak pressures aren't really high without any load.

I've now taken the car to an Audi mechanic who will replace the head gasket, timing belt, tensioner, water pump, etc.

I'll get back to you after the replacement to let you know how the head gasket really was, because it should be possible to tell if the head gasket was actually faulty once it's removed, right?

Best regards,
Andi.

By the way, I've just checked, and my 1994 AAT doesn't have an oil cooler!

Andi aus dem Ösiland wrote:

... I'll get back to you after the replacement to let you know how the head gasket really was, because it should be possible to tell if the head gasket was actually faulty once it's removed, right? ...

Unfortunately, it's unlikely.

Hi,

I'm revisiting this topic.

'Recently, I've started experiencing the exact same problem (oil in the coolant) as described by Andi at the beginning. Interestingly, it's also happening at a mileage of 165,000 km.'
No water in the oil, no external leaks on the engine, etc.
The only differences are my slightly lower fuel consumption, which is about 1 liter less... and the working fuel injection control piston .

Does anyone have any new insights on this?
I'm particularly interested in Andi's opinion (I also sent you a private message), whether it was the ZKD (thermostat) or the heat exchanger!

I want to identify the most likely cause so that I don't have to replace both parts.

Based on a discussion in another thread, the ZKD (cylinder head gasket) seems less likely to be the issue, as drivers of vehicles with AAT/AEL engines are still using the original gasket without problems, even with mileage ranging from 250,000 to 320,000 kilometers.
/viewtopic.php?t=5909

Rainer K. wrote:

Was the engine really pushed to its limits during the test?

Hello,

If the leak in the cylinder head gasket is between the oil channel and the coolant channel, then the pressure in the combustion chamber is irrelevant, or (the blow-by test has no effect)? However, if this is the case, coolant could potentially flow into the oil after the engine is turned off (p oil < p water), if the pressure of the coolant (approximately 1.2 bar) is sufficient.

What is the oil pressure in the cylinder head of a TDI engine under full load?

Good morning!

@ Markus H.

The AAT definitely does not have an oil/water heat exchanger (unless it was delivered from the factory with a trailer hitch attachment)! After the fact, no one could confirm whether the head gasket was actually defective (but where would the oil be coming from otherwise?). Unfortunately, I haven't been able to thoroughly clean the container yet to see if there is absolutely no oil left inside or coming from the cooling system! I haven't noticed any changes after the replacement (except for the corrected static pump start).

Something different that might be interesting to me: Does your AAT really need 1 liter less than mine?? Maybe I should still replace my ESP .
My driving habits: I drive approximately 80 km on the highway every day, at speeds of around 150-170 km/h (using the 5th gear).

Best regards,
Andi.

Hi,

Thank you for the (unfortunately bad) news.
I heard from christianS here that mine might have a heat exchanger. I'm not sure about that myself yet.

I will not be replacing the ZKD right now. I refuse...
Besides, there's no water in the oil.

Regarding consumption:
He consistently fluctuates between 6.5 and 7 liters, and has now been at a surprisingly precise 6.67 liters for quite some time.
Daily commute: 100 km on the Rhine-Ruhr highway (very congested, but travel speed 180 km/h if possible) + 20 km on country/city roads.
Sure, here's the translation:

'Oh yeah: 5-speed transmission + air conditioning.'

Hi,
@MarkusH

I just noticed that you have an AAT, not an AEL. What Andi said still applies, but it's still worth checking.

Hi,

@christianS:
Okay, I will do that too.
It wasn't meant as an accusation towards you!
I should actually know myself whether he has one or not...

But my question is actually almost completely answered - he probably doesn't have one.

I will definitely carefully observe the further developments for now.
If the pink coolant actually turns black, or if there's water in the oil, then something needs to be done.

Hi,

to briefly revisit the topic:

It's gotten worse now - there's a thick, greasy, black sludge layer in the expansion tank. However, the engine is running completely normally. It has 180,000 km on it.
Okay, so it's now confirmed that the head gasket will be replaced on Monday. It's not as bad as it could be, because they'll also be replacing the timing belt, serpentine belt, and water pump at the same time. Still, it's going to be expensive...

My question arises from the following statements made by an Audi master technician:
1. There should be NO oil in the coolant, but a lot of soot.
2. This is likely because an asbestos gasket was installed before the end of 1993, which was not strong enough. As a result, soot enters the coolant with each combustion cycle.
Therefore, Audi also resorted to using a metal gasket. Unfortunately, my Audi 100 still has the asbestos gasket.

--> Does anyone know about this issue ?

I'm interested in this because it would almost rule out a hairline crack in the head or block. I'm a little worried that the problem will persist even after the cylinder head gasket is replaced.

Yep, I know that.

My old AAZ engine had the same problem. With the new metal head gasket, the pre-combustion chambers were also changed at the same time.

It's possible that your cooling system will be flushed to remove soot residue. Make sure this is confirmed in the cost estimate beforehand. In my case, the invoice later included €130 for this service. After I complained, they gave me a €100 discount.


Regards...


..... Kuhni!

Okay, I can tell you a story:
I bought my 1Z with 144,000 kilometers on the odometer.
"I'm a very careful driver, but over time, I started to get oil in my coolant. So, I even replaced the head gasket myself at 170,000 kilometers. It even had an asbestos gasket! I still have the gasket lying around; there are no visible defects, but the material is quite soft and can be easily crumbled with a screwdriver."
I didn't know that it was asbestos until today .
Today, 181,000 km and everything is still sealed.
I flushed the cooling system with a radiator cleaning solution and cleaned the expansion tank with nitrogen. Everything is clean now.

Attention: In my DIY book, the torque specification for the asbestos gasket was listed. Thankfully, I double-checked that information.

I don't think it was rust in my case.

I know of two other people who had the same defect with the same vehicle model and similar mileage.

Hi,

@Kuhni and wolfi_b:
Sure, the cooling system will be thoroughly flushed. It probably won't be completely clean anymore, but the point is to see later if replacing the head gasket helped.
Similarly, for my master, planning the head is also part of ensuring safety.

There's generally nothing wrong with asbestos - it's not living space (except for martens...).

Okay, okay. Then the Audi master was right.
Unfortunately, it was still too expensive, so now my 'local mechanic' (a former VW and Porsche master technician) is going to take a look. Also, VW is unwilling to provide the necessary parts. I myself don't feel confident enough to do the job, and with my lack of experience, I would probably have to deregister the car for as long as it would take.

I'm not familiar with the design of your coolant reservoir. However, depending on the design, you may need to completely fill it to see any bubbling.
You don't necessarily have to drain it all out; the engine will get rid of the water on its own before it becomes a problem. Unlike with oil...

The fact that there is no water in the oil, and that you likely aren't burning either water or oil, doesn't mean it's not a catalytic converter issue. The catalytic converter could be acting like a membrane, allowing flow in only one direction.