Coolant gets hot, interior doesn't

Hi,

I've spent 2 hours searching through every possible resource and haven't found anything about it.

Bei meinem TDI wird das Kühlwasser in normaler Zeit warm (Überprüfung durch Kanal 51 in der Klimatronik) und steht auf ca. 90°C. Das Zeigerinstrument für das Kühlmittel braucht etwas länger. Es wird wohl von einem anderen Temperaturgeber versorgt. Gleichzeitig wird der Innenraum nur sehr langsam warm. Die Austrittstemperatur an der Defrost-Düse beträgt bei Stellung HI, mittlerer Lüfterdrehzahl und - um eine weitere Fehlerquelle auszuschließen - mit abgeschalteter Klima nur ca. 35°C. Eindoften too little.

What I have already checked and found out:
The coolant thermostat is functioning correctly. The lower hose remains cold until a temperature of approximately 90°C is reached.
'The radiator cooler is not clogged. I disconnected both hoses and used a garden hose to pump water into one hose, which flowed freely out of the other hose.'
'When I tried to inject water into the cylinder head using a garden hose, I encountered back pressure. Is this normal, or is there a serious blockage?'
4. The heating valve, which is controlled by vacuum pressure, is functioning correctly. If the vacuum pressure control were not working properly, the valve would be open anyway (fail-safe mechanism).
5. There are no error codes stored (channel 1 in the climate control system) (display shows 00.0).
6. The white levers that control the air vents move when you adjust the temperature setting from completely cold to completely hot.
7. There is no air in the heating system's expansion tank. No air is escaping from the bleed screw located behind the heating valve.
8. The climate control system seems to be registering the hot water and constantly increasing the fan speed. Unfortunately, the calculated temperature increase inside the car doesn't occur because the air is only lukewarm, so I have to manually reduce the fan speed.
9. Der obere der beiden Schläuche zum Heizungskühler (der, in dem das Heizungsventil sitzt) ist nur mäßig warm, der untere ordentlich heiß. Meine Diagnose dazu: Entweder findet ein extrem guter Wärmeabtransport im Heizungskühler statt - dann müsste es aber im Innenraum schön warm sein, oder es wird keine Wärme übertragen. Das kann aber nur sein, wenn das Wasser nicht strömt. Das wiederum kann nur sein, wenn kein oder nicht genug Wasser nicht aus dem Zylinderkopf austritt, weil dort vielleicht eine Verstopfung sitzt. IcUnfortunately, in a closed system, I can't see how much water is flowing through.
10. The water pump is new.

In which direction should the water flow? Should it go from the lower hose to the radiator and then back through the upper hose via the heater valve, or vice versa? Shouldn't it also be possible to introduce water into the cylinder head using the garden hose so that it can freely exit through the other opening, just like with the radiator? And this in both directions.
'Anyone have any advice? The cold season is starting, and even with a TDI engine, I'd like to stay warm!'

In which direction should the water flow? Should it go from the lower hose to the radiator and then back through the heater valve via the upper hose, or vice versa? Shouldn't it also be possible to introduce water into the cylinder head using the garden hose, so that it can freely exit through the other opening, just like with the radiator? And this in both directions.
Who has advice? The cold season is starting, and - even with a TDI engine - I would like to be able to sit comfortably in a warm car!

Hi there,

The water is leaking from the cylinder head where the three glow plugs are located within the flange for the electric preheating system. From there, the water needs to flow to the heating radiator heat exchanger.
Has anything like 'radiator sealant' ever been used in your car?
What does the coolant look like?
Greetings.

Eike.

Based on your description, I agree that something seems to be blocked.

Hello Eike,



From there, the water must flow to the heating heat exchanger.
Has anything like 'radiator sealant' ever been used in your car?
3. What does the coolant look like?
Greetings.

Eike.

PS: Deiner Beschreibung nach stimme ich Dir zu, daß etwas verstopft zu sein scheint.

Okay. Then I'll disconnect the hose and see how strong the water jet is. Does anyone have experience with how much water should be coming out per minute?
'As far as I know, no. I've had the car for 3 years, and this effect only became noticeable to me last winter, so it was a gradual development.'
'3. When I flushed the system with the garden hose, a few black particles came out. Now it's been refilled, and the coolant looks like fresh coolant with antifreeze.'

From there, the water must flow to the heating heat exchanger.


PS: I find it very surprising that the inlet hose is colder than the outlet hose. In an extreme case, this would mean that the coolant in the heat exchanger is *absorbing* heat instead of releasing it!

From there, the water must flow to the heating heat exchanger.


PS: Then I find it very surprising that the inlet hose is colder than the outlet hose. In an extreme case, this would mean that the coolant in the heat exchanger is *absorbing* heat instead of releasing it!

Hello,

mit ZUlauf meint er wohl die Seite, von der das Wasser ZU dem Motor ZUrück läuft.
It simply can't be any other way. Or are there cases where the water pump pumps in the wrong direction?
If there is also a temperature difference and a minimal heating output, it's reasonable to assume that the flow rate is very low. The question is, why?

Greetings.

Eike.

dcjf wrote:

In which direction should the water flow? From the lower hose into the radiator and back through the upper hose, via the heating valve

SIC.

Yesterday, I also noticed the following:

At higher speeds, the heating performance improves significantly. Perhaps the water pump can then circulate the water more effectively. This also suggests a possible blockage. As I mentioned, the displayed temperature is above 80°C even at low speeds.

Who can recommend a laxative to me?

Hi,
Unfortunately, I'm not familiar enough with the internal structure of our engines to know if there's a throttle or anything similar located somewhere. However, I would try securely connecting a garden hose and applying pressure at various positions. Perhaps this will dislodge any dirt or foreign objects that might be causing the problem.

Today, the heating performance seemed very low again. After driving over 20 km under moderate load – with the coolant temperature at approximately 85°C – it only reached a temperature of about 22°C inside the car (measured with an extra thermometer at head level), even when set to the highest setting.
And now, channel 01 is displaying a '15.6' error. Maybe I should check the air flaps after all. It would be a nice explanation if the car isn't getting warm inside because too much cold air is mixing with the warm air due to an air flap that isn't closing properly.
Does anyone know how I can do this without taking everything apart?

Hi there,
As far as I recall from the documentation for the climate control diagnosis, it is possible to query the position of the actuators, but not to actively influence them.
However, if the supply temperature to the heat exchanger is only 85°C after 20 km, then it's possible that the thermostat is responsible.
I had a similar problem; the car barely got warm at lower outside temperatures (the coolant temperature gauge showed slightly above 70°C, and according to the climate control system, the flow temperature to the heater was around 82-87°, even after driving for 20 km or more). Replacing the thermostat then resulted in the flow temperature, as indicated by the climate control system, reaching 92°C within a maximum of 10 km, even at -5°C, and the water temperature gauge also showed approximately this value.
The hose below the thermostat was also cold before, and the new thermostat has at least the same part number as the old one.

Olli.
96' A6 C4 AEL 242,000 km

@Olli

Well, the thermostat is almost new. Maybe something is stuck inside that's preventing it from closing properly. I've experienced something like that before. Thank you for the tip, I'll take a look.
My idea regarding error code 15.6 (faulty fresh air flap) was that something might be stuck there, perhaps because the friendly mechanic forgot his 10mm open-end wrench inside when he changed the pollen filter.

Hi there,
Have you ever tried to turn the climate control on?
Then the supply of outside air should be almost completely eliminated...

Regards,
Olaf.

Yes, you can activate the recirculation mode. You hear a sound from a vacuum pump and a closing flap – well, that's the sound you know. But it doesn't change the heating power. Isn't it the case that this recirculation flap is located before the hot air flap? Is this the same flap that is referred to as the 'Staubluftklappe' (dust air flap) in the Climatic system? Maybe I have mentally confused this flap with the hot air flap, which allows air to flow over the radiator when heating and not when cooling.Please provide the text you would like me to translate from German to English. I need the text to be able to give you a translation.

Apparently, it seems that there was indeed a blockage.
After driving approximately 10 km on the highway at around 150 km/h with a warmed-up engine yesterday (usually I drive a maximum of 120 km/h), it seems the blockage has cleared. Afterward, the interior became pleasantly warm, and the displayed temperature in 51°C no longer decreased when I drove slower. This morning as well, the interior warmed up relatively quickly. During this time, the needle for the coolant temperature only rose very slowly.What was that? dQ/dT = dm/dT * c * (t2-t1). Because the heat exchanger is now flowing through with a larger mass flow rate (dm), it can also transfer more heat into the interior. At the same time, this heat is missing from the engine, which means it takes longer for the engine to warm up.
Previously, the temperature difference between the supply and return heat exchanger was very large because 'dm' was so small. Does that make sense? Or does anyone have a different explanation for it, perhaps involving earth currents, aliens, coincidence, or paranormal forces...?

So, if you actually had such a large blockage in the heat exchanger that hardly any coolant was flowing through, and it has now dissolved... Well, cheers to that... Now this debris is going through your engine and may settle again in other places. At first, you won't notice anything, but over time, it could lead to localized overheating. Therefore, I would strongly recommend a coolant change with thorough flushing as soon as possible.
Aber evtl liegt die Ursache doch woanders. Gerade weil dein Gartenschlauchtest ja gezeigt hatte, dass dieser nicht verstopft war. Völlig ausgeschlossen ist für mich die Lufttheorie noch immer nicht (obwohl du schreibst, daß an der Entlüftungsschraube keine Luft kam). Bei längerer hoher Geschwindigkeit hast du auch längere Zeit hohe Drehzahlen und damit höher Wasserströmungsgeschwindigkeiten. Dadurch könnte die Luft dann mitgerissen worden sein und nun im Kühlmittelbehälter geladet sein. Bliebe 'The only question is how the air could have gotten there all of a sudden.'

But the most important thing is that everything is working again now. Maybe change the coolant for good measure, and just hope for the best.

Regards,
-Private

Hi there,
I also suspect there might be an air bubble trapped somewhere. I haven't specifically examined the coolant system in this car yet, but I've definitely seen it happen in other cars where even a small amount of air in the wrong place can prevent the thermostat from opening, causing the water to boil relentlessly in the cylinder head. Properly bleeding the system can sometimes be tricky.It certainly wouldn't hurt to check the consistency of the coolant in the expansion tank, just in case the theory about a blockage is correct.

Regards,

Olli.