willk47

I too recently had my fittings welded. Within a month I had a "coolant temp failure" light come on. My temperature gauge went to zero. It would come back on and off periodically. It also seemed like a series of hard bumps in the road would cause it to fail. So I'm thinking the sensor or wiring was damaged with the welding. Taking it in next week. Will let you know what he finds. He says he's heard of this problem before when the fittings are welded.

Craig911

Let me know what you find out. The air temperature has warmed up here into the 50's for a low and I have not had a problem with the temp gauge failing either on the street or an autocross last weekend but it still takes awhile to come up to temp when I start with a cold engine.
What's weird is after the autocross I had a hotter than normal engine as expected, then drove home on the freeway about 75 mph and had the gauge dip down to way below normal after about 5 min cruising. It then goes back to normal when idling or driving through side streets. It never used to do this before i had the fittings welded.

993GT

^absolute prime example of failed thermostat

452gt3

Craig, it's maybe too simple but has anyone tried bleeding air from the system?

Mike

Craig911

Not that I know of, I will check it next time I take it in. I assumed air was bled when they refilled the system after the fittings were fixed but probably not since then.
Thanks,
Craig

Audisportwerks

HAS ANYONE RESOLVED THIS ISSUE ? I have the exact same issue on my 2003 gt3. New temp sensor and tstat were installed but didn't reolve the issue.

LoveTheBeast

I also have the exact same issue on my 2002 GT2. Thermostat and sensor have been replaced and lines checked for air and the problem persists. I am also interested if anyone has resolved this issue.

ScottArizona

I'm betting air in the system. The coolant system on all 996 cars are notoriously hard to completely bleed without the factory tools. I'd rule that out first.

TurboCup87

^^^^ This.

LoveTheBeast

I had the air bled from the cooling system and the problem still persists, so we can cross that one off the list.

Audisportwerks

System has been completely bled of air after t-stat and temp sensor replacement. also has been driven 300+ miles and still has same issue. could the IPD plenum and 997 TB have anything to do with this?

996FLT6

There's that thingie ma jig spring thingie on coolant expansion tank that u can open up expansion vent by pulling it upwards. Drive it for 30 minutes check coolant level add as needed and drive again 2 more times for 30 minutes. Getting rid of air bubbles in pressurized coolant system ain't that easy. Also bear in mind temp sensor could be damaged as result of welding or worse welding wasn't done well. I had mine pinned- never had that issue. Mike

edgy

I got this same issue guys, I posted about it here https://rennlist.com/forums/996-gt2-...nsor-fail.html and got referred to this thread.

Has anyone actually fixed it? Has anyone tried changing the thermostat.. My car has not been apart to have the fittings pinned or welded yet.

sergio75

i had the same issue and got it fixed 18 months after discovering it and bringing the car to a series of porsche specialists and official dealers in the area of Paris, France.
i am not a specialist in mechanics but here is what i understood from the porsche dealer who finally succeeded in solving this issue: the cooling system of our gt3s crosses the gearbox. at the level of the gearbox there are two pipes connected to depressurize the cooling circuit. when the two pipes get reversed, the cooling system works but the temperature gauge falls at zero and indicates a default when the water temp reaches around 50°C ; and then works again when the water temp reaches 70-80°C.
the tricky part is that those pipes look similar and so it is very easy, even at official porsche garages to get their connection reversed.
hope this helps.
serge

Craig911

Has anyone else managed to fix their coolant temp gauge issue by switching the coolant pipes as described in this last post?

I am the OP on this thread and I still have the same problem over the last two years despite replacing the sensor and bleeding air out of the coolant system. I've learned to live with the issue by simply warming up the engine at idle on cold mornings. It is still slow to reach temperature but I hate throwing more money at fixes that don't work for a minor but annoying problem.