Water Temp Indicator Failure!

[p3.6996]

Hi All,

I got in my car for a drive from Leics to Heathrow to pick up the enemy. Within a few minutes the red light at the top of the water temp guage started to flash and a warning 'indicator failure' refering to the water temp guage. At first i was quite worried and pulled over a few times to check the water but everything okay.

During the journey this happened quite a few times (about 20 times on this 300 mile journey), it would be okay and show the temp, then it would fail giving the warning and slow flashing light. When working the temp reached just over 60 which usually sits at just over 80, indicating 20 less than 'normal'. As this was reflecting cooler water temp i hoped it would not be an issue. Better cool than hot! On the way back from Heathrow the temp guage decided to work for the whole journey but still sat at just over 60.

Summary:

It would work normally but temp would sit at just over 60 degrees, then it would fail, bleep once, state water temp indicator failure and the red light flashes slowly. After some time it would decide to work but again back to the begining as it would report water temp of just over 60 degrees etc etc.

The car drove perfectly but this happened many times during my 300 mile journey on the same day.

Can anyone help??

It is a 2002 996 Facelift Tiptronic C2.

Thanks

[1999Porsche911]

A slow flashing light would indicate low coolant level. Check level of reservoir.

[RFM]

Sounds like Tiptronic cool water/oil exchanger problem. The water valve is vacuum controlled, in normal temps. and driving conditions the exchanger is shut off (vacuum on the valve). In case of 1) leaking vacuum tube 2) defective valve membrane 3) defective solenoid or electric wiring, the exchanger (receives no longer vacuum) is now always active in the engine cooling system, the engine will run 20°C cooler. If the engine runs too cold as programmed, after a long drive, the red lamp comes in as "implausible signal". Let this check first, before changing the thermostat, temp. sensor, etc.

[1999Porsche911]

Thermostat would not cause this symptom. The DME will only cause the temperature gauge light to flash slowly under 2 conditions. 1) Reservoir sensor is reading low coolant level or 2) the engine compartment temperature is too high or sensor bad. Your engine cannot run at 60C no matter what is correct or wrong with your cooling system and therefore, your reading on the temperature gauge is not accurate. As with all computer controlled systems, all sorts of things can be effected my a short, lose wire, etc.

If your coolant level is normal, it is possible that the temperature sensor is bad and this is the easiest part to replace. Cost is about $30 US. However, a common symptom of a bad sesnor is an idle that runs higher than normal, taking longer to drop back to normal. Also, check the connection to the level sensor at the bottom of the reservoir.

Have you had any work done on the engine recently? Coolant change, etc?

Edited January 24, 2009 by 1999Porsche911

[Richard Hamilton]

Sounds like Tiptronic cool water/oil exchanger problem. The water valve is vacuum controlled, in normal temps. and driving conditions the exchanger is shut off (vacuum on the valve). In case of 1) leaking vacuum tube 2) defective valve membrane 3) defective solenoid or electric wiring, the exchanger (receives no longer vacuum) is now always active in the engine cooling system, the engine will run 20°C cooler. If the engine runs too cold as programmed, after a long drive, the red lamp comes in as "implausible signal". Let this check first, before changing the thermostat, temp. sensor, etc.

That's the same diagnosis a Porsche tech on PCGB 996 forum gave to this problem - ie a loose or dislodged vacuum pipe. I guess it's quite a common problem.

[RFM]

Correct Richard, it happen once in a while, Tiptronics are specific in trouble shouting concerning cooling issues. It is by the way the cheapest and quickest way to go, to check this out first, no parts needed, just a lift and 10 minutes of your time.

[Porschekid]

Sounds like Tiptronic cool water/oil exchanger problem. The water valve is vacuum controlled, in normal temps. and driving conditions the exchanger is shut off (vacuum on the valve). In case of 1) leaking vacuum tube 2) defective valve membrane 3) defective solenoid or electric wiring, the exchanger (receives no longer vacuum) is now always active in the engine cooling system, the engine will run 20°C cooler. If the engine runs too cold as programmed, after a long drive, the red lamp comes in as "implausible signal". Let this check first, before changing the thermostat, temp. sensor, etc.

That's the same diagnosis a Porsche tech on PCGB 996 forum gave to this problem - ie a loose or dislodged vacuum pipe. I guess it's quite a common problem.

Anyone have a link on a write-up for this? P3, ever solve your problem? I'm seeing a similar problem on my Tiptronic 2001 996 Turbo.

Edited May 12, 2009 by Porschekid

[mcbit500]

Sounds like Tiptronic cool water/oil exchanger problem. The water valve is vacuum controlled, in normal temps. and driving conditions the exchanger is shut off (vacuum on the valve). In case of 1) leaking vacuum tube 2) defective valve membrane 3) defective solenoid or electric wiring, the exchanger (receives no longer vacuum) is now always active in the engine cooling system, the engine will run 20°C cooler. If the engine runs too cold as programmed, after a long drive, the red lamp comes in as "implausible signal". Let this check first, before changing the thermostat, temp. sensor, etc.

This happened to me in the 996 C4S Tip for the first time this morning, when it recovered the gauge was reading 60C after which it slowly rose to 80C.

Based on this a couple of questions:

What is the source of the vacuum which operates the disc valve?

Since I've had the car I've thought that it warms up a little slowly. Its winter here now so morning starting temperature is around 20C. In the CTT coolant is at 80C in 3-4 minutes and oil temp at 90C about 7 mins after starting. Since owning the C4S it has taken at least 10-12 mins for the coolant to reach 80C; is this normal for a 996 3.6L engine at this starting temperature?

Any feedback appreciate, thanks.

[amadmutha]

Did ypu find the issue as i have the same issue.