991.1S “Cooling Fault - Visit Garage” - Page 1 - 911/Carrera GT - PistonHeads UK

Anyone else had this error pop up? It’s booked in for next week, but the fault goes away after a few minutes. It doesn’t appear to get a reading from the thermostat but after a minute or two it does and the error disappears again.

The 9x1 range have a vacuum controlled thermal management system; a collection of solenoids fed vacuum from a engine driven pump switch at specific times to control warm-up and heat dissipation once up to operating temperature. Other things like sports exhaust and transmission cooling are also controlled using the same system. The DME monitors the vacuum in the system and flags an issue if an expected value isn't attained - total loss of vacuum will be felt at the brake pedal (no assistance). Diagnosis isn't too dramatic - measure the vacuum and if it's within spec, monitor it as and when the solenoids are switched; if vacuum cannot be built up at first then a leak is likely (or in extreme cases the vacuum pump has failed). Once certain the vacuum is correct, it will be monitored after switch-off (a leak in the system can be found at this point by clamping off the solenoid input hoses one by one. If the system is leaktight up to now the solenoids can then be switched one by one - a loss of vacuum after a solenoid is switched highlights a faulty circuit after the specific solenoid (spilt or disconnected hose) or component (a split diaphragm in an actuator for example). On 991.1 there are up to 8 solenoids (inc. sports exhaust control). The solenoids have been modified since the 2013 release of the car and they require upgraded connecting looms if being replaced (later ones seem to be far more reliable; which is nice). Later models have a vacuum switchable coolant pump too - coolant can get into the system and cause a few issues...

Pope said: The 9x1 range have a vacuum controlled thermal management system; a collection of solenoids fed vacuum from a engine driven pump switch at specific times to control warm-up and heat dissipation once up to operating temperature. Other things like sports exhaust and transmission cooling are also controlled using the same system. The DME monitors the vacuum in the system and flags an issue if an expected value isn't attained - total loss of vacuum will be felt at the brake pedal (no assistance). Diagnosis isn't too dramatic - measure the vacuum and if it's within spec, monitor it as and when the solenoids are switched; if vacuum cannot be built up at first then a leak is likely (or in extreme cases the vacuum pump has failed). Once certain the vacuum is correct, it will be monitored after switch-off (a leak in the system can be found at this point by clamping off the solenoid input hoses one by one. If the system is leaktight up to now the solenoids can then be switched one by one - a loss of vacuum after a solenoid is switched highlights a faulty circuit after the specific solenoid (spilt or disconnected hose) or component (a split diaphragm in an actuator for example). On 991.1 there are up to 8 solenoids (inc. sports exhaust control). The solenoids have been modified since the 2013 release of the car and they require upgraded connecting looms if being replaced (later ones seem to be far more reliable; which is nice). Later models have a vacuum switchable coolant pump too - coolant can get into the system and cause a few issues... Thanks, I’ve already had a solenoid go in the left cylinder bank a year or two ago. Engine went limp and a nice man from Porsche Assistance towed it to the OPC for a new one. I wonder why it seems to right itself after a minute or two. It’s booked in for Tuesday so hopefully they can sort it quickly enough.

I suppose if the solenoid in question controls warm-up - once it's up to temp that circuit is no longer required; the warning will drop away.