JFiRB

I have visited my dealer for 4 times during my 4-month ownership. This time the "service engine soon" warning came on. It turned out the engine thermostate is broken (jammed open). It is an important part of the engine's cooling system. Do you guys think there is any harm done on my engine? I drove another 40 miles before dropping the car to my dealer.

I also googled this issue. It turned out quite a few people have this problem. And it is because BMW use cheap plastic thermostat housing (something like that). Have you guys heard of it?

Ray Hull

Not familiar with it on your model, but there have been many complaints on leaky radiators and bum waterpumps on E39s--usually after 40-50K miles.

Should be no threat whatsoever to your engine; were it the opposite, overheating, then you'd have a worry. Cool temps might just make it run a bit richer, but nothing serious.

Cheers,
Ray Hull

JFiRB

Thanks. This is what I was hoping for. I just didn't know what is the exact effect of running a cold engine.

BERM

I had the same warning last week, I went to the dealer and they told me that the thermostat is bad. They replace my thermostat next day and couple days later the massage is back again. So I dropped my car in the dealer last Tuesday and today they will let me know what was wrong with my car. My service advisor also mention something about some bulletin that is out regarding thermostats in new 3series, and maybe there is some connection between these two cars.