[WRichieX]

Hey guys, so I'm looking for some explanation to make sense of this. For a couple months, I had a thermostat code and check engine light. I'm due for emissions and cleared the code and took it to get my emissions hoping to just slide right through. Of course I failed the first time. So I ordered a thermostat from Tischer and I believe it's going to come in this week so was planning on doing it this coming weekend. However, last week, I changed out my air filter and cabin filter. In addition, I rewired my backup cam as that was throwing a code as well. So in that process, I cleared codes again. Since then I never got a check engine light and car seemed to be warming up fine. I went to emissions today and I passed. What's going on and what happened? Could weather be a factor as well? It has been pretty warm the last few days in Chicago. I'm expecting it to fail soon again, but can the thermostat magically fix itself out of nowhere for awhile?

This kind of thing happened in my G35 before as well. I had an o2 sensor "go out". Left it alone a couple months and then magically went away too and never had a problem for a few years till it flooded and got my 335i.

[3s4u2]

Give it a few more months, it will be back...

[E90Graphite07]

Sounds like mine. Thermostat is getting stuck on the open position. Do you notice the oil temp takes a while to warm up? The SES light will go on/off over time...

[TiminCT]

Sometimes an intermittent thermostat is a sign of a water pump bearing seal failure. When you shut the car down, the coolant leaks back down and hides on the plastic sump protector, and when you drive away- it disappears. Eventually, you leave it for a day or two, try to start, and the pump can't "prime" : A dry thermostat won't open, and the coolant prevents vapor. the old auto transmission cooler lines were a notorious "hidden cause." The reservoir system (above the Tstat), usually maintains flow, but hey, stuff happens sometimes.

Not necessarily the case here, but you seemed like you were fishing for theories. I've seen the scenario above play out more than once. Waterpump, T-stat and Radiator are like 60k mi oilchanges on a BMW.

[WRichieX]

Originally Posted by E90Graphite07

Sounds like mine. Thermostat is getting stuck on the open position. Do you notice the oil temp takes a while to warm up? The SES light will go on/off over time...

For a couple months, the oil temp seemed like it would never warm up. The last week after all the things I did, it warmed up perfectly and quickly. Like when I first got the car. Now I'm confused.

[E90Graphite07]

Originally Posted by WRichieX

For a couple months, the oil temp seemed like it would never warm up. The last week after all the things I did, it warmed up perfectly and quickly. Like when I first got the car. Now I'm confused.

Sounds like you're having the same problem. My SES would switch off when the weather got warmer. Let me remind ya that I'm on my original TS/WP, running at 112K miles. So it literally is 'timed' to get it serviced indeed. If it was stuck closed, then it would overheat and cause damage to your engine.

[WRichieX]

Originally Posted by E90Graphite07

Sounds like you're having the same problem. My SES would switch off when the weather got warmer. Let me remind ya that I'm on my original TS/WP, running at 112K miles. So it literally is 'timed' to get it serviced indeed. If it was stuck closed, then it would overheat and cause damage to your engine.

Yea my tstat came in today but I may hold off to install it. Wait to see what happens. Maybe my WP may start to go in a bit too then do it all together. lol I'm right under 70k mi and all original.

[WRichieX]

So my SES light came back on 2 days ago. Checked the code and sure enough Tstat. But a day later, went away and no code. Could it be a connection issue? Anyone try a spraying some choke cleaner or MAF sensor cleaner on it to fix? I had a MAF sensor "go bad" and sprayed some MAF sensor cleaner on it and the electrical connection on my G and that totally fixed it. I was talking to some mechanic folks and they said that they spray choke cleaner on electrical plugs (said Choke cleaner and MAF cleaner is pretty much the same) to clean it cause that could be what's causing issue if it keeps going out but ok again. Or should I just replace the tstat since I have the part. I really wanted to wait till my WP starts to fail and do both.