Coolant Leak: Causes and How to Find It

Hello forum,

I have an Audi A4 TDI with a 1.9-liter engine, 110 horsepower, manufactured in December 1997, and it has 270,000 kilometers on the odometer.

For the past few months, I've been noticing a coolant leak that occurs every 2,000 kilometers.
Approximately 1 liter.

I've already had the car raised on a lift several times and have thoroughly searched for the leak, but there's nothing visible externally.

The hoses appear to be okay, and the various engine seals seem fine from the outside. There doesn't appear to be any water in the oil (everything looks nicely black on the dipstick and oil filler cap). There is no oil in the coolant reservoir.

So far, my assumption is:

'The head gasket is leaking water into the combustion chamber, and the water is escaping through the exhaust. How likely is this, and is there a way to diagnose it?'

'The cylinder head has a leak, and exhaust gases are entering the cooling system, forcing water out through the expansion tank. How likely is this to happen, and what's the diagnostic process?'

3) There's a leak in a hidden location, for example, inside the heating system's heat exchanger or somewhere else within the interior.



What do you think? The timing belt needs to be replaced. Should I have the head gasket changed as a precaution? Or should I just sell the car and look for something new? Actually, I wanted to drive this car until 360,000 kilometers...

Regards,

Michael.

So ein Problem hatten wir ebenfalls bei einem A4 AFN. Zur Überprüfung (weil kein Wasserverlust und auch kein Druckaufbau zu erkennen war), habe ich den Überlauf des Ausgleichsbehälter mit einem Schlauch angezapft und in eine provisorisch befestigte Cola Flasche geführt. So konnte man feststellen, ob überhaupt Wasser heraus gedrückt wurde. Da das nicht der Fall war, haben wir eine Dose Kühlerdichtmittel dem Kühlwasser zugeführt. Seitdem It is quiet.

Quote:

What do you think? The timing belt is due for replacement. Should I have the head gasket replaced as a precaution? Or should I rather sell the car and look for something new? Actually, I wanted to drive this car until 360,000 kilometers...

Pour a bottle of radiator sealant into the cooling system. If that doesn't help, from a business perspective, I would consider selling the vehicle.

'@BM I actually have a bottle like that hanging in my engine compartment already, since yesterday.'
'A few milliliters have already leaked in, but I think it's still within the normal range so far because I had tilted the expansion tank almost completely full.'

I'll wait and see how things develop after driving about 1000 km. If the coolant reservoir starts to fill up, then it's definitely a problem with the head gasket, right?

I will also consider the tip about using a radiator sealant after the first 1000 kilometers. Is there a specific brand that you would recommend? Could it potentially cause more harm than good in some cases?

OFFTOPIC:
'Do you have to disclose a coolant leak when selling a car, or would it be better to mention it in a subordinate clause, like 'it leaks a little coolant'? I wouldn't sell a private buyer a car without mentioning it; maybe only a dealer.'

Regards,

Michael.

Quote:

I'll wait and see what happens after 1000 km and observe how it develops. If the bottle fills up, then it's definitely due to a problem with the head gasket, right?

If the cap, water pump, and thermostat are working correctly, and the radiator is leaking, then there's a 99% chance that's the problem.

Quote:

I will also consider the tip about using a radiator sealant after the first 1000 km. Is there a specific product that is recommended? Could it potentially cause more harm than good in this situation?

Wynn's, Holts, or Tune-Up are all suitable products. It's important not to overdose; use only one bottle. I am not aware of any damage caused by proper usage.

Quote:

OFFTOPIC: "Does one actually have to disclose a coolant leak when selling a car, or would it be better to mention it in a subordinate clause, like 'it leaks a little coolant'? I wouldn't sell the car to a private individual without mentioning it; maybe only to a dealer

."

Well, actually yes, even if it's a shortage and even if it's a dealer.

Hello,

'It seems other people with the same vehicle are experiencing the same problem. It was the head gasket. Before it finally failed after a full-throttle run, I occasionally heard gurgling and hissing noises from behind the dashboard when starting the engine. These were gas bubbles being forced from the combustion chamber into the coolant and accumulating there.'

Regards,
Harry.

had the same problem with a similar vehicle. It was the head gasket. Before it finally failed after a full-throttle run, I occasionally heard gurgling and hissing noises from the dashboard when starting. These were gas bubbles that were being forced from the combustion chamber into the coolant and settling there.


It was the same for me. I can only confirm it. New cylinder head gasket and everything is sealed tight.

Okay: Pressing the button didn't give me any results. Exhaust fumes are much 'thinner' than coolant.
Basically, nothing actually entered the system; instead, exhaust gases were added, which caused the coolant reservoir to 'overflow' or 'foam over.'

Best regards, Kassen.