[bimmerbene90]

To start off I'd like to say hello. I am new to this forum and am anxious to learn more about my car and to share some of my knowlege as well. I love BMWs new and old.
I currently have a 2006 330i.

About a month ago, while driving to work, my car lost power and the temp sensor went yellow then red and the car went into limp mode. After towing it to the shop, I began to diagnose the problem and found that after adding coolant that it seemed to be running fine. I wasn't convinced so I read and asked a lot about it and found that it was a common problem on the e90 for the electrical waterpump to malfunction after 65k. I replaced it and was told the thermo was fine. After replacing it, I have been driving the car quite a bit with no problems.

Yesterday....while driving the radiator sensor came on yellow. When I got home I popped the hood and noticed a leak. It was coming from the top radiator hose, it was busted on the inseam of the bend. I have now replaced the hose but am very worried that it has been running hot for some time now and that is what busted the hose.

With no temp gauge on the e90, I asked how I can check to see if the cooling system is working properly. I was told to check if that same hose has pressure. I started it and let it run for 8-10min and got no pressure but the fan did not turn on either. So I'm not sure if it was even warm enough for the thermo to open.

If anyone has any advise I would greatly appreciate it. I just don't want to run it till it overheats again risking the gasket and block.

[AlanAZ]

Hey there, did you search on water pump or thermostat?

The thermostat defaults to open position if it fails. Typically over-heating conditions are causing by the water pump beginning to fail. Often round 100K mls -- you didn't state your mileage. Best to replace both at the same time. Search for and buying them on-line will get you the best price, if you can replace them yourself, there's a DIY in that forum.

[queensfield]

Have you been loosing coolant slowly after the water pump replacement? Perhaps, a pressure test of the entire cooling system may reveal why overheating might be occuring. If water pump is new and working, and you are loosing coolant or failing the pressure test, then overheating is understantable. Like Alan said, a failed thermostat will not explain overheating since it fails open.

[ENINTY]

Get an OBD-II scan tool that can read live data. Start the car, warm it up, drive it round with the scanner recording data and see what the coolant temperature settles at.

[Abdi]

Hey guys,

I don't want to hijack this thread but I think I have an identical issue and hope we can find a solution together.

Anyway, I have a 2006 330i with 111,000 miles and same exact issue on Friday; first the yellow overheat icon, then red overheat while simultaneously spewing out of the reservoir cap and going into limp mode. The heater was blowing cold air now too. It was about 35 degrees out in Western MA and I had the heat on.

Keep in mind that I am literally about to trade this car in at the end of the month. So I drove it home about 2 miles away while coasting in neutral on an empty back road and it appeared that the temp cooled off a bit as the yellow over temp icon illuminated again.

I am thinking that the water pump is failing as is common for BMW's but I am not certain of this for a couple of reasons.

1. After searching this forums all weekend, I did the coolant drain and fill DIY and the pump was audibly working when I performed the bleeding process.
2. P0597 (Thermostat heater control circuit open) code leads me to believe that I might only have a bad thermostat.

I am a 16 years experienced airplane mechanic with lots of tools so I will replace whatever component is required but I honestly would like to spend a little money/time as possible prior to trading it.

best regards,
Abdi

[queensfield]

A failed thermostat, which is in the open condition, will not cause overheating- it just won't allow your engine temperature to reach optimum point. Your water pump is likely dying, as you also stated. They die intermittently. To be sure that it is the pump, pull the shadow codes using an OBDII reader that can read BMW codes. If you are going to trade the car, I am not sure you want to fix the water pump. They are very expensive (near $500).

[Three_thirty_I]

Interesting thread! E46's were also known for having troublesome cooling systems, so to play safe it's a case of replacing the typically affected components before they fail and cause the engine to overheat - I gather it doesn't take long for an overheated engine to develop severe damage, so ideally want to prevent this from happening. Not having a temp gauge in the E90 is annoying since you are at the mercy of the electronics picking up on the engine temperature being too high etc.

I have had two bad experiences with service agents, so much so that I would prefer not to let them near any of my cars ever again! So will most likely have to invest in an OBDII reader for myself!

My car has just over 60k km on the clock but is an '05 model, and about to go out of service plan, so cooling system is probably still fine, but might not be a bad idea to keep a close eye on it and consider replacing some of these costly, but problematic parts...