I am new to posting so bear with me. I have a 2007 997.1 with tiptronic. I have had CEL come on with codes P2181 and P3081. I have changed the thermostat and the coolant temp sensor and re-set the lights. It will throw the same code(s) after driving a while. The temperature comes up very slowly (probably takes 15 to 20 minutes of driving to get to the normal 175F(83C)) mark and it stays there. This tells me the new thermostat is working properly. I checked the old one and it was closed at ambient temps and opened up in hot water so it was actually working but i already had the new one (and housing) so no big deal to change. I have read somewhere that there is a transmission disc valve that is actually another cooling system that also can be faulty and allow water to circulate and it can extend the time it takes for the engine to reach the normal temperature. However, it is unclear if all 997.1's have this valve or just the GT3 which is what the information I saw stated. Once the engine gets to normal temps, the CEL does not come back on but I either have to allow it to idle to come up to temp or drive like snail for it not to throw the codes.

So, the question is, anyone had this issue before? Does anyone have any information on the transmission disc valve?

 

Unfortunately I can't help you with the "transmission disc valve", however, I can say from experience that 15-20 minutes for the coolant to come up to temp seems a bit long. I realize the coolant temp gauge is a bit of a dummy gauge, holding steady at 175F for the most part. In the Spring/Summer months here in CO, from the time I leave my driveway until the time my car shows 175F coolant temp under normal driving conditions, is about 5-7 minutes. For my oil temp to get to 180-200F is about 12-15 minutes typically.

What have your oil temps been showing recently?

 

Oil temps are also slow to come up. But they run in the same range as you mention.

 

I had the CEL on my 07 C2 Tip come on a few days ago while on a leisurely drive so hooked up my Foxwell NT520 Pro and it showed code P2181. I did notice the water temp was slower than normal to rise, but oil temp was showing a normal. I cleared the code and all was well until CEL returned today with same P2181 code. Found this post on porscheclubgb.com mentioning a bad change-over valve which is mounted next to the disc valve: https://www.porscheclubgb.com/forum/tm.aspx?m=969310

Will do the recommend troubleshooting and report back.

 

Thanks for the follow up. My disc valve was fine, it was the vacuum switch. Part number 99660512301 (change over valve). I changed both parts while I was under there so all is good now. Warms up as it should and no codes!

 

20 mins to get to 175 COOLANT temperature is way too long, even with a LTT. I would start there.

 

Update...I my earlier post I had the temps reversed - should have noted my water temp was showing normal but oil oil temp was slower to rise. I ordered a new Disc Valve (Item #8, Part #92857457303) and Change-Over Valve (Item #13, Part #99660512301) from FCP Euro ($60.77 total w/ tax + shipping). Finally had a break from the heat in DFW today (85 instead of 105) so I replaced both and did a 30 minute test drive with no codes. Took about two hours total including setup and take down of my Quickjack lift. Once the plastic cover below the transmission is removed both are easily accessed. Only lost about 2.5 oz of coolant which I topped off afterwards.



Old valves in place

Crimped coolant lines on Disc Valve

New valves installed