hollywood1053

Will be replacing my 997.1 water pump soon and am thinking of installing a LTT at the same time.
I've read about many people here doing the same citing various reasons.
I mentioned it to my Indy when I asked for a quote and he recommended not using a LTT for street use.

"The lower temperature version could trigger a cooling system fault code because the engine would take longer to warm up .... It could also trigger catalyst efficiency fault codes depending on the driving conditions."

What are your thoughts on this?
Has anyone experienced fault codes after installing a LTT?

ADias

I would not do it either. Not good IMHO especially in cold days. Hot days it does not matter, soon enough the engine will be hot.

roadie13

I have never heard of the LTT triggering codes. But I also have not installed it either, because I don't like the oil running that cold during regular street driving in winter. I am just very careful about running the engine during the first 10 minutes, not idling, revs 2-2.5K w/o lugging. On the track the LTT does not matter, which is where my other application is

chiefm3

Isn't the purpose of the LTT to start cooling the block sooner so that the rear cylinder (I think #6, most notorious for bore scoring) doesn't heat up as much as it does with the stock thermostat? In the end won't the engine still reach the same temperature, it's just a matter of when the T-stat opens up - which with the LTT since it opens sooner it will slow down the ramp up rate of temperature in the engine?

roadie13

I haven't got the numbers handy but the LTT starts opening at pretty low temperatures, naturally, which does not matter if this is purely transient and the engine gets up to full temperature. But puttering around in winter can leave the oil temperature at a fairly low level if doing that, so I personally don't like that my oil is not close to water boiling. Still, most folks on here love the LTT so just my minority opinion

fuzebox

It definitely takes longer to heat up, especially in the winter. It's kind of frustrating especially when trying to both stay under a certain RPM, but also not lug the engine, since I live in a hilly area.

I accept the tradeoff, after reading LN Engineer's take on it.

Petza914

Unless you live where it's really cold, it won't do either of those things the mechanic mentioned. I've had LTTs in both my 997s for over 10 years and don't have any errors. It's the single most significant thing you can do to prevent bore scoring by allowing the engine to warm up more gradually and prevent excessive heat at the end of the cooling system path, which is guess where, cylinder #6, and which one scores most prevalently, yep, cylinder #6.

Petza914

LTT opens at 160 vs the 180 of the standard one and is fully open by 185 whereas the 180 degree version isn't fully open until over 200.

cwheeler

Use the LTT. The brightest minds working on the M9X platform all suggest and use it. The slower warm up isn't a big deal. In cold temps (~30*F), yes it takes a few more min to get to 200* but, it'll still get there. The safety is provides is more important than than the 5 extra min of warmup.

thurm33

I ordered and installed a low temperature thermostat (Warner) myself several months ago. I have been getting a CEL for the engine not reaching optimal temperature in a normal range. I've cleared the code a couple times but it keeps coming back. I've read that this has happened to some after LTT installation, but what have people done to correct it? Do I need a PIWIS to clear the code? Could the LTT be bad? Could I have installed it wrong? The engine does eventually reach 175+ F, but it takes awhile (as it should). Curious to any thoughts.

Petza914

.1 or .2 car and what's the outside temp when this is happening?

thurm33

It's a .1 C2. The codes came on with the outside temp at 50-65F but not cold. I think it made it through the warmer summer months without getting a code. I'm getting a p2181 code. I checked my coolant level and it is good.

Petza914

How many miles have you driven and are you sure you've removed any trapped air from the system? Did you vacuum fill it or just fill up the reservoir? Did you move the HVAC to full hot to open the heater core to let the coolant circulate and push out any air?

I recall my 997.1 c2s did this on the first drive after I stalling a LTT and have never done it again in 13 years. I wonder if it kind of needs to learn the new behavior to consider it normal and if resetting the code keeps starting the learning process over. Maybe drive it a few times just ignoring the code and see if it stops coming on at some point.

thurm33

Thanks for the help, Petza.

Looking back at my records, I did the LTT install in May 2022 and have put about 2,000 miles on since then. I did buy and use an Airlift tool to add coolant back in, but it was my first time doing that so I guess there could be air in there - but probably unlikely. I don't recall if I ran the HVAC on full hot afterwards but wonder if I could do it now to test it. Should I keep the

I recall the coolant temp dead/not operating at all after install, but leaving the battery disconnected for awhile reset the system and no longer had that issue. I don't recall the first time the p2181 code coming up, but it definitely has occurred a few times this year. I don't recall any issues over the summer, but when temps got lower this fall and it took longer to heat up the engine, the CEL came back. I have cleared the codes the last time hoping it would resolve itself, but it came back after <20 miles of driving in cool temps. I've cleared them again recently but will see, if it comes up again, if I can put a lot of miles on it so it learns (doubt this will work). Also, not sure if it's related, but I did have to replace the battery after it died a year ago (I actually still need to get the system scanned to allow my seat heaters and homelink to work).

I have found this thread of a guy that seems to have the same issue I am having (also used a Warner LTT). The OP replaced the "failed" LTT with a second LTT and the issue seemed to go away, but he goes on to guess that the first LTT was not properly installed because it looked like it was functional. Any thought on that? I'm trying to avoid the whole process again of installing another thermostat.
https://rennlist.com/forums/cayenne-...ck-open-2.html

Petza914

2,000 miles is plenty to have worked any air out of the system. If you'd only done 30 or so and hd reset it a few times, that may have been a possibility, but not after 2,000. The only thing I'd check before deciding to swap it for a new LTT (and I'd buy it from LN Engineering) is that your coolant temp sensor plug is properly connected to the sensor and that that contacts are clean, especially since you said the gauge didn't register at all after installation. If the DME isn't getting good data from the sensor it might be throwing this code.