P0381/cooling gauge stuck

[mihaipopa]

Hello everybody,
Just a quick question regarding my 04CS. Been really freezing for the past couple of weeks, and the truck have developed some heating issues. It started about ten days ago with the heat not working until after being driven for, I don't know about 30 miles. Same symptom once or twice, always in cold mornings. Today, it happened again, but on top of that, the coolant gauge on the dashboard never moved from the 100 baseline. The engine also felt cold at touch, the warmest part was the coolant reservoir. I turned it on and noticed a strong air flow blowing from both the front of the engine, from the radiator fan area under the hood, and from the air vents on the bumper. I also pulled code p3081.
Coolant pipes have been done a couple years ago, coolant tank replaced last year. I had refreshed the coolant in the summer also, uview vacuumed, pressure tested, refilled w genuine stuff. No coolant leaks/smell as of today.
I'm about to order a coolant temperature sensor (part# 99660641000)
What do you guys think?

Safe to drive?
Any input would be greatly appreciated.
Thanks

 

ps just noticed that the thread title says p0381..sorry, I meant p3081

Edited February 17, 2015 by mihaipopa

[Pkscheldt]

Sure sounds like a thermostat that is stuck open. 

[mihaipopa]

Thanks pkscheldt,

Would it be a terrible idea to drive it that way, till I get to fix it? I know a closed thermostat is out of question, but an open one?

[Pkscheldt]

I wouldn't drive it that way, I'm guessing it's a stuck open thermostat, but ???? Not a common Cayenne issue I'm aware of.

 

On my M5 I had a stuck open thermostat on the way in to my office with near Identical symptoms and then it became a stuck shut thermostat on the way home and it was a disaster - 7 mile commute.

[wvicary]

The cooling fans operating, fault code and the garage not indicating point to a failed coolant temperature sensor, the part has been updated and be sure to replace the sealing O-ring and the retaining clip when doing to sensor.

[wvicary]

Just another note: verify the water pump is actually circulating coolant. With the engine cold, remove the pressure cap, start the engine and observe coolant circulating in the expansion tank at the upper bleed hose.

[mihaipopa]

Thanks wvicary,

will check the water pump when I get home. As for the sensor, I ordered it from ecs, it's part 99660641000, and I hope that is the latest version. In the pictures it looks like the o-ring is included and the retaining clip would be the plastic part on the left..?

This morning I got heat in the cabin within ~5 minutes of drving; the dashboard coolant gauge stayed at zero, and the front fans made the same jet noise. No leaks, engine definitely felt cold at touch. 

Should I hold onto ordering a new thermostat then? I dread the idea of dealing with all that coolant nonsense again, especially at 20 degrees. 

Thanks again for your input

[mihaipopa]

there's the sensor (on Pelican a search for 99660641000 actually describes the part: Engine Coolant/Oil Temperature Sensor (includes sealing ring)

[wvicary]

Sorry the V6 using the oring and clip and the V8 threads into a coolant passage. Thermostats are rather reliable so I would just replace the temp sensor and retest. You'll need to clear the fault codes after sensor replacement.

[mihaipopa]

A bit of an update: so yesterday I received my new coolant sensor from ecs (promptly as always, thanks ecs!) and today I went ahead to check the water pump per wvicary's instruction (thank you for the tip) and it seems like the pump works just fine. However, after I put the cap back on the reservoir I left the engine running and what I noticed was that the cooling fans on the radiator stopped making that engine jet noise, and the engine felt warm. On top of that, the coolant indicator on the dashboard slowly went to the 180 mark, where it settled.

The only variable that has changed since last week would be the outside temperature.. Today, it was around 40, so above freezing point. Everything else on the car stayed the same.

Now, does outdoors temperature affect the coolant sensor?

I mean I will get it replaced anyway, just curious here.

Thanks guys, I'll report back.

[JFP in PA]

A bit of an update: so yesterday I received my new coolant sensor from ecs (promptly as always, thanks ecs!) and today I went ahead to check the water pump per wvicary's instruction (thank you for the tip) and it seems like the pump works just fine. However, after I put the cap back on the reservoir I left the engine running and what I noticed was that the cooling fans on the radiator stopped making that engine jet noise, and the engine felt warm. On top of that, the coolant indicator on the dashboard slowly went to the 180 mark, where it settled.

The only variable that has changed since last week would be the outside temperature.. Today, it was around 40, so above freezing point. Everything else on the car stayed the same.

Now, does outdoors temperature affect the coolant sensor?

I mean I will get it replaced anyway, just curious here.

Thanks guys, I'll report back.

 

Ambient temperatures should have no impact on how the sensor performs.

[mihaipopa]

Thats what I thought too. I just don't get it..Car's been parked all this time, coolant level hasn't changed, there are no leaks, no smells, no codes, all the symptoms just suddenly gone. I'd normally be happy with not having to fix things, but this just seems odd, and I have a feeling that it's not really over. Plus, reading all the horror stories of scored cilinders especially in cold climates caused by compromised cooling systems, I'm reluctant to even start it up.

Puzzled here..I guess I'll go with changing that sensor first.

Thanks for reading, any input will be highly appreciated.

[JFP in PA]

Thats what I thought too. I just don't get it..Car's been parked all this time, coolant level hasn't changed, there are no leaks, no smells, no codes, all the symptoms just suddenly gone. I'd normally be happy with not having to fix things, but this just seems odd, and I have a feeling that it's not really over. Plus, reading all the horror stories of scored cilinders especially in cold climates caused by compromised cooling systems, I'm reluctant to even start it up.

Puzzled here..I guess I'll go with changing that sensor first.

Thanks for reading, any input will be highly appreciated.

 

I'd keep a close eye on it for a while, you could still have an underlying intermittent thermostat issue.

[wvicary]

The temp sensor can be intermittent, just replace the unit and monitor closely for any other issues.

[mihaipopa]

Hi guys,

 

Just wanted to report back. I changed the coolant temp sensor about ten days ago and monitored everything closely. Car's been driven daily, mixed city/highway.

All the symptoms are gone and the gauge works well, settling at 180º. Code P3081 never returned. The engine warms up evenly. No coolant leaks observed; coolant level in reservoir at constant level.

I changed the sensor without removing the manifold, and although it's a bit difficult due to lack of space and visibility, it can be done with a bunch of extensions and sockets. I actually put together a diy, hope it comes in handy for the next person.

Thanks again for all your help.

 

Cayenne V8 coolant temp sensor.pdf

[wvicary]

Positive result.

[JSP]

I am having a similar problem with my 08 Cayenne turbo. When it is very cold outside and driving a short distance the radiator fan runs at high speed and the temperature gauge reads normal or a bit below normal, ac/defrost off. The heat is working good, turn off the heat and the rad fan still runs full blast until I turn the key off. I had replaced both fans due to the corrosion problems with the modules and that time the rad fan ran all the time full blast and stayed on for 30 seconds after the the key was turned off. The current problem is intermittent and only happens when it is very cold around -10 C  or lower outside. It has 177000 km and I don't think that the thermostat or water pump have been replaced yet. I have read elsewhere that the water pumps usually fail around this mileage. Should the water pump and thermostat be replaced as preventative maintenance along with the coolant temperature sensor? The service records show that the leaking thermostat housing was replaced at 76000 km

[AirShox EU LTD]

On 3/3/2020 at 3:51 AM, JSP said:

I am having a similar problem with my 08 Cayenne turbo. When it is very cold outside and driving a short distance the radiator fan runs at high speed and the temperature gauge reads normal or a bit below normal, ac/defrost off. The heat is working good, turn off the heat and the rad fan still runs full blast until I turn the key off. I had replaced both fans due to the corrosion problems with the modules and that time the rad fan ran all the time full blast and stayed on for 30 seconds after the the key was turned off. The current problem is intermittent and only happens when it is very cold around -10 C  or lower outside. It has 177000 km and I don't think that the thermostat or water pump have been replaced yet. I have read elsewhere that the water pumps usually fail around this mileage. Should the water pump and thermostat be replaced as preventative maintenance along with the coolant temperature sensor? The service records show that the leaking thermostat housing was replaced at 76000 km

What happened? Did you repair the issue?

[JSP]

Hi,

 

My European mechanics at TSH Auto in Toronto found that the A/C pressure switch located near the fire wall was malfunctioning and turning on the Fan. They used a scan tool to help them diagnose the problem. I used Bluedriver scanner app. to monitor my engine temperature which showed the temperature fluctuating 20 -30 degrees below normal. My mechanic found that the thermostat was stuck partially open and it was replaced, the previous owners service records show that Porsche replaced the thermostat before, when the housing was replaced. The water pump had to be removed to get to it but it was found to be in very good condition, therefore I was not able to claim this on my aftermarket warranty.

[JSP]

These were two separate issues that happened at the same time. The A/C pressure switch is not expensive and not too much labour to replace, however replacing the thermostat involves more labour and is a lot more expensive to replace than normal. I suspect that the thermostat was probably stuck for a while.