tarasok

Hi guys,
I have strange issue with cabin heating. It takes 15-20 min after engine start when I feel that warm air started blowing.
Typical Behavior (Settings: Mode: AUTO, cabin desired temp 22°C (72°F)
1. Engine start, outside 0°C (32°F),
2. In 5-7min cold when engine warmed up, cold air 3-4 °C (~38°F) started blowing.
3. In 15-20 min warm air start blowing (the main issue)
4. When temperature in cabin reaching to desired 22°C (72°F), air blowing reducing.... (works as expected)

Expected behavior: Warm air should start blowing in 5-7 min after engine warmed up...

Investigation:
After reading many related topics, I found that there might be heat coolant valve (95857281000), I replaced it, but still the same behavior.

See below recording how I reproduced issue:

garrett376

Which Cayenne model?
And you have confirmed your engine actually warms up in 5-7 minutes? If so, what temp is the coolant at in 5-7 minutes?

tarasok

Model: Cayenne 3.6L V6 2017.
in 5-7 min coolant temperature 80°C (176°F), oil temperature 45°C (113°F), air temperature from heating 4°C (39°F).

dollarlongnecks

Have you tried to add any coolant to see if it's low? Sometime the overflow tank will look full but will still accept additional coolant.

tarasok

I tried to add coolant before heat coolant valve replaced. It didn't help

tarasok

Today is a little bit warm weather. Coolant temperature become 60°C (140°F) in 3 min and climate control started blowing cold air. It became warm in 20 min

wkearney99

What happens if you use the front defrost button? Putting it int 'HI' mode. Does that air also stay too cold for too long?

Has anything been done to the vents? There are air temp sensors in them, but I confess to not knowing the specifics of which ones are involved.

tarasok

Defrost or temperature set to HIGH didn't help... I don't know if smth was done to vents...
I did some additional measurements and noticed that warm air start blowing from vents when coolant temperature becomes 90°C (194°F) and oil 70°C (158°F) and it takes 15-20min to reach such temperature.
I also noticed that there is some kind of dumper before radiator (see image), It should be closed when engine is cold. But it is almost always open, even engine is not started (but today when I turned engine off, I saw it is closed).

• Regarding engine temperatures... is it possible to configure programmatically to start heating when coolant temperature reached ~60°C (140°F)?
• Could issue be in always opened dumper before radiator, so it takes 15-20min to reach coolant temperature 90°C (194°F)?

wkearney99

Does the outdoor temperature read reasonably accurate on the MFD screen? There's a temperature sensor in the front end that provides it. You can configured the MFD (the small round multi-function display) to show it. I have it on the bottom row in my '17 GTS.

Because if that's wrong then that might affect how the systems decide to manage the engine compartment ventilation. I think the general HVAC term for such things is 'damper' but I don't know what Porsche calls those. In the manual they're called "Cooling air flaps".

In the parts database I believe they're part of the the 'radiator shutter assembly': https://www.porscheatlantaperimeterp...850532102.html

A search here on 'shutter' or 'flaps' brings up a number of posts that might be worth reading to get more diagnostic info.

Simeon

The radiator shutters are usually used for improved aerodynamics. When the engine doesn't need so much cooling, keeping the shutters closed reduces the drag force on the car due to improved airflow around the nose and reduced pressure in the engine bay. So they should be closed most of the time, BUT if temperatures are below/near freezing, the shutters may be kept open in case they accidentally get frozen stuck. So they make sure if they do get frozen stuck, they would be in a position where the engine can get the cooling it needs.

Nonetheless, I don't think the shutters should impact the HVAC heating in any way. They may potentially slow down the engine warm up a little bit, due to colder air flowing into the engine bay, but the thermostat will still do it's job and let the engine warm up before coolant starts flowing through the radiator.

Somehow you must not be getting hot coolant flowing through the heater core, but why is the question.. When you replaced the coolant valve, did you bleed air out of the coolant system somehow? Instead of using auto, just use 'Hi' temp setting for a while to try to let as much coolant running through the heater core as possible. Is it possible you installed the coolant valve incorrectly or it is not connected if it's electrically operated (haven't looked into how this valve works)? Did you check the fuse for this valve if it is electrically operated?

I just realized that I have a service manual CD for the Cayenne and can look up diagnosis procedures for this. Will let you know when I do.

tarasok

Thanks guys for your reply!

yes, outside temperature is accurate.
Coolant valve was replaced by official dealer, I don't have details how they did it. They also tested car (using PIWIS) after valve replacement and said everything is fine, no errors.
I set HI temperature and behavior is same. When coolant temperature reached 90°C (194°F) and oil 70°C (158°F) warm (even hot) air starting blowing from vents (before such temperature airs blows, but it is really cold). Outside temperature 4°C (39.2°F).

Today's updates:
I noticed that cooling air flaps were closed today even I started engine (I couldn't verify if they become open when I was driving) and when I arrived and shutdown engine in 30min - they were still closed). So, when flaps were closed, I saw same behavior, in ~15-20min engine coolant temperature reached 90°C (194°F) and oil 70°C (158°F) and warm air started blowing from vents.

wkearney99, what coolant and oil temperatures are in your Cayenne when you start feeling that warm air started blowing from vents?

Simeon

Are you saying that it took 15-20 mins for the coolant temp to reach 90C? If that is the case, you would have a stuck open thermostat. Coolant should reach close to 90 C within 10 mins or less even on a very cold day.

tarasok

yes, it depends... sometimes it is faster, but usually it takes 15+min.

Today I did additional testing and noticed next things:

• Air flow system works as expected, in AUTO mode, when oil temperature reach 20-25C (77F), then air stream become higher, when temperature in cabin is reached, air stream is lower.
• Even air stream becomes higher, it is still cold... and become warm when oil temperature reach 70°C (158°F).

So, Air management system works as expected, start blowing air quickly and stop (reduce) blowing when cabin temperature reached. However, heating starts working only when oil temperature reached 70°C (158°F).

garrett376

If I were in your shoes, I'd be replacing the engine thermostat.

Simeon

I agree.. this definitely sounds like a thermostat if it takes so long for the engine coolant to warm up.