[LowercaseD]

So I have had a bunch of smooth running codes and some other random stuff and while I was looking at the data in ProTool I noticed my coolant temp was really low. Like 60c at best. So I finally got around to replacing the thermostat and when I loosened the bolts the spring part just fell right out. It looks like the tabs that hold it in broke off.

Has anyone else had that happen? I imagine that the tabs are somewhere in the cooling system. Also the egr bolts were almost stripped and the bottom one fell into the engine bay somewhere. Looks like tomorrow I’m getting out the magnets and trying to fish it out while I wait for new bolts.

[BB_cuda]

I'm surprised the E90 upload tool let you use those high resolution pictures. Normally it makes you use smaller files. they are huge to look at.

Back to your report. I have seen other posters provide same story of broken parts. So the coolant was flowing continuous through the radiator. BMW should change the design to a metal housing to make those ears stronger or somehow embed metal ears into the plastic molded housing. I'm sure this will never happen as M57 is an old design. Good luck finding the EGR cooler screws. I always take off the lower splash shield to see better and let tools and parts fall all the way to the floor. I hate when something falls and you don't hear it hit the ground. So many places for things to hide.

[nonford]

My thermostat was exactly the same, what a design.

[Owen81]

Yes, like almost everyone....

For your smooth running codes, check out this post.

https://www.e90post.com/forums/showp...4&postcount=56

[LowercaseD]

It does make you wonder. At least that’s reassuring that everyone else’s broke in the same way and that other peoples cars didn’t die when those plastic pieces got caught somewhere in the cooling system.

Thanks for the link on the smooth running codes. I have been meaning to take the intake off to check for carbon build up also.

[barf]

Its common for that to break. New thermostat is dirt cheap though and quite easy to replace.
Smooth running controller is usually caused by injectors.
There is a compensation of individual injector fuel quantities at idle and low load so all 6 injectors are spraying equal magnitutdes. They will start to differentiate due to age related processesses which i wont go into. I dont know if there is a big thread about this already but I know a lot about that topic and could make a thread if there isn't one. On how it works, how ecu calculates it etc.
Coolant temperature will not play a big part in that, well the values will usually get better when engine is up to temp but you shouldnt get them anyway. Run the INPA or ISTA service program where you can see what are the values of compensation.
Beware that DPF does not regenerate if coolant temperature is low, i think it needed to be over 70C but i could be incorrect.

[LowercaseD]

So I finally got around to doing the thermostat. Getting to the egr cooler bolts on the exhaust manifold is not super fun but the rest went well.

Temp holds at 88c without much fluctuation and nothing seems to be leaking.

I would love to learn more about how the smooth running control works. What values it looks at and how it measures them. Even if I end up just having a carbon build up issue it’s always great to learn.
Thanks,