All,

I've had some ongoing issues with the cooling system. I've owned the car for 5 years, even in the hotest summer (50c) I can run it in low range (so low speed, high RPM) and it will not go past mid point on temp gauge.

recently ( past few months, its been going up to 3/4 mark on temps. It also doesnt sound like fans are running at 100%. This only happens offroad, in at high RPM, and low range / or low gears. I.e. when the car is going slowly (less than 30kph), but there is alot of engine revs. I cant replicate this behavior on road.

My garage had failed to fix it. But we've done the following
- fixed open thermostat (just to remove as source of issue)
- replaced water pump (as we were doing thermostat)
- replaced main fan on radiator
- flushed coolant system

I've just ordered an Aux fan, as it may be that. Temps seem to read correctly on the durametic.
The issue is I cant work out how to test if the system is working correctly. Or understand fully how the ECU works. I can statically run car up and cover front radiator with plastic to simulate the car getting hot, but not sure what to measure to ensure its working as designed. (I've just been checking that the fans come on).
I've also tried to test that the run on when engine is stopped works, but again dont know the expected behavior.

Does anyone know the proceedure to perform a static test of the cooling system and determine its working effectively?

I'm feel like I only have the ECU and temp sender (which I am sure is correct) left to change after this fan replacement.

regards

Hugh

 

This sounds like the electric Auxillary fans are not running, or running fast enough

 

Agree, hence I've now ordered the second fan. The issue is how do you run a static test to correctly verify. I cant simulate the condition, without taking car offroad into the desert. Driving on road and running statically I dont actually know how to test it the system is working 100%.

 

Does the aux fan come on when you turn on the AC? It is supposed to come on low speed whenever the AC is on. The high speed is triggered by a temp sensor. You would need to get the car really hot to check it in the car, so pull it and put it in boiling water and check the resistance across the polls cold and hot. That should narrow it down to a sensor or fan controller. There are some fuses also to check

 

Both Fans run, but I'm not sure they run at 100% - its hard to tell. And yes, aux fan runs when A/C is on. Temp sensor appears to be sending right temp, based on Durametric values and the guage in the car. In normal driving the fans seem to do their job, and there is some run on after engine is of (although this is short).

I'm not sure under what conditions the fan should run 100%, or if you can see the fan running speed on a durametric. Also, I've read that the FCM takes car speed into account, but not sure if thats true.

 

Interesting issue. I think you're on the right path. Can you verify that in the past you haven't had the issue in the exact same circumstances?

I ask this because I've experienced some similar issues when towing over the past decade. Lower speed, higher rpm the coolant gauge would creep to about 2/3 to 3/4. Nothing would drop the temperatures beyond lower rpm or faster speed.

One last item to check is the aux coolant pump. I don't know if GTS's have one, but CTT's do. It's located behind the drivers side wheel liner on the aft end of the wheel well. It activates when the temps get very hot. You can hear it running on hot shutdowns.

Assuming it's none of the above. I'd remove the radiator and clean the air conditioning condenser, blowing it out from behind. It's probably clogged with debris or bent fins. Result would be a significant drop in cooling efficiency.

 

Thanks for the feedback...some comments.

Whilst I cant say for sure it has never gone to 3/4. I have regularly been out and done runs and watched the temp and it hasnt climbed to 3/4. I do know last summer I was doing low range climbs of sand dunes in 50c ambient heat and the temp gauge was still in the middle. Now its going to 3/4 all the time, and its only 35c ambient temp outside so the behavior is definitely different.

The Aux coolant pump is a good one to check - I've no idea if the GTS has one. I'll need to go and look......

Then I think you are right, removal of the radiator and AC condenser blowing from behind is a good idea. Its probably packed full of sand, which would cause a reduced efficiency.

The trial and error approach seems to the only way to diagnose the problem, so I think that's what I'll end up doing. I've got 3 things I can follow up on. Would be nice to be able test them to determine cause, as well as test before I commit to going into the desert again.

 

Hi, the issue for me is that the temp sensor looks like a real pain to get out. As in Manifold off job. Will do it if left with no option. The problem has moved on a bit....Post below.

 

OK folks, an updates. I've replaced the A/C fan now, so both fans are replaced. I've also realised that the durametric reads the fan % signal. If I take the car for the run, then park and block the radiator with plastic, I can get the car to heat up. With the engine at about 107 C, the aux fan runs at 99%, but the main fan runs at 55 -60%. I never get the main fan to run at over 90%, even with the temp up on 3/4.
I am also getting code 0481 on the durametric, Looking this up I get. Its clear, I need to some diagnostics.
Can someone confirm is Fan Module 2, the small one, or the big one. I definitely seem to have a run issue with the big one. I tempted to try to put 5v to the input of the main fan, and connect a 12v battery to the large terminals, to see if I can get it run 100%, that would suggest a wiring issue, temp sensor or DME issue.

Does anyone know what the temp reading from the coolant temperature sensor is in Durametric
Does anyone know how to force the main fan on at 100% in the durametric?

I need to learn how to use the Durametric more, and understand how to troubleshoot the electrics a bit better. I dont really understand how to circuit check the DME signals.
------------------------------------------------------------------------------------------------------------------------------------------
Fault P0481

Fan control output stage 2 - open circuit/below limit value/above limit value

Diagnostic conditions

• Time after the engine is started longer than 10 seconds

Possible cause of fault

♦ Break in wiring in power supply to fan module 2 (small/to the left)

♦ Short circuit to ground in control line to fan module 2

♦ Short circuit to B+ in control line to fan module 2

♦ Fan module control module 2 faulty

♦ DME control module faulty

OBD-II Trouble Code Description for P0481 Porsche

Fan 2 Control Circuit

What does this mean?

OBD2 Code P0481 Porsche definition:
The electric cooling fan is controlled by the powertrain control module (PCM) through the cooling fan relay based on inputs from the following components: – The engine coolant temperature (ECT) sensor – The intake air temperature (IAT) sensor – The A/C selector switch – The A/C refrigerant pressure sensor – The vehicle speed sensor (VSS) The PCM controls the cooling fan by grounding the cooling fan control circuit which turns ON the cooling fan relay. The cooling fan relay will be commanded ON when the following conditions are met: – The engine coolant temperature reaches 106¡ãC (223¡ãF) or more. – The A/C clutch requested. – The vehicle speed is less than 38 MPH. The cooling fan relay will be commanded ON regardless of vehicle speed when the following conditions are met: – The engine coolant temperature is 151¡ãC (304¡ãF) or more. – The A/C refrigerant pressure is high. The cooling fan may be commanded ON when the engine is not running under a fan run-on conditions described in the electric cooling fan general description portion of the service manual.

Symptoms

Possible sumptoms of OBD code P0481 Porsche
– Engine Light ON (or Service Engine Soon Warning Light) – Engine overheating

Causes

Possible causes of OBD code P0481 Porsche
– Fan control relay harness – Fan control relay connector – Fan control relay – Cooling Fan 2 The Error code is generally activated on detection of the following conditions: The P0482 Porsche code is detected when the PCM detects that the commanded state of the driver and the actual state of the control circuit do not match.
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I would be looking to replace the temp sensor first. Good thing is they r cheap. Bad thing is there is no way to accuratly test one because Porsche did not publish the NTC curves. You could always grab a new one and make your own chart but why waste the time.

 

Hi thanks for the quick response.

You may well be right - but its a real pain in the *** to replace. Is there no way to check what it's reading with Durametric? I'd hate to go to all that effort and find its actually something else.

I think what is also killing me is, I replaced the thermostat and waterpump, and we didnt do the temp sensor. :-/

 

NTC- Negative Temperature Coefficient

If the sensor is jacked it doesn't really matter what Durametric is telling you. Most of these type of sensors have a linear curve. Like I said, to test it properly you need values for resistance vs. temp. You could reverse engineer this from a new sensor to make a chart and test your current sensor in place I suppose. Kinda like stepping over a dime to pick up a penny. Thankfully Porsche fix it program is to throw parts at cars instead of performing proper diagnosis to the core. There is no need for them to supply this information to even their trained tech's because it isn't part of their business model and neither are thrice removed customers.

A burnt up engine can be a real PIA as well. Maybe not for me but for you guarunteed.

 

Hi,

Again, many thanks. I think you are right. I'm just looking to achieve 2 things before I do that work
1. Check the fan will run at 100% (force a signal from Durametrric or elsewhere
2. verfiy the wiring ti good, and its not a break down of wriing that is killing signal, before I rip the manifolds off.

regards

Hugh

 

Had the same problem on my SO's 08 CTT. I think my mechanic might have found the issue :-)

Attachment 1303652

 

Well thats pretty clear. Out of interest, did you get the same error code. Both my fans definitely turn. But the main fan never runs over 44%, even when coolant is at 100.