[julianbos16]

Hello everyone,

My BMW E90 318i with the N43 engine (185.000km’s) has some problems with heating/cooling.

About two months back I was driving on the highway for about 15min’s and it was very cold in the car. After leaving the highway I got a yellow temperature warning and the car went into limp mode.
So I found a spot to stop, and checked the coolant level. It was below min.

Slowly drove to a shop, refilled the coolant and voila, the car was driving perfect again. I had heat in the cabin and the temperature of the car was fine (since then I’ve been measuring the temperature with an OBD-II scanner.

Did a bleeding process at home. Water pump was pumping the water around fine while bleeding.

I kept an eye on my coolant, but it hasn’t dropped since. I haven’t had a yellow temperature warning light either.


However, about 1 month later, the car is having problems with heating the cabin, and also the coolant temperature is increasing rapidly (and high)

Most of the times at morning, when its relatively cold outside (around 1-3 degrees celsius) the car doesn’t heat inside the cabin, no matter how long I drive. While I have no heat inside the cabin, the cooling temperature runs upto 110-115 celsius, before I shut the car off.

I have had this happen about three times now. Two out of three times, when I restart the car (while the coolant temperature is at ~110 degrees celsius), I instantly get hot air inside the cabin, and the temperature rapidly drops from 110 —> 106 —> 103, all the way to 88-90 degrees celsius. For the rest of those drives, everything was working perfectly,

Last weekend, it was around 12 degrees celsius outside. And the engine was cooling fine, I had heat inside the cabin. Everything was working fine.



To me, it is almost like there is something blocking the coolant from reaching the engine, and heater core, when it’s colder (1-3 degrees celsius) outside.

Water pump seems fine to me, since after the restarts, the coolant was continuously at ~90 degrees celsius

My guess is the thermostat, but before I replace anything I would like to receive a second opinion.

If anything is unclear, don’t hesitate to ask for more clarity.

Thanks in advance!

[gbalthrop]

I'm NOT familiar with 318i N43 ECE models, but you MAY have a Water Valve (Y4a in attached ISTA ScreenPrints), which shuts
off or admits Hot Coolant to Heater Matrix. See attached ScreenPrints showing electrical circuit, Location, & Connector View.
Your description suggests an intermittent fault in JBE Activation of Water Valve, perhaps an issue in Yellow/Brown "Activation"
wire between JBE & Valve, particularly at Valve Connector, X85.

It is likely that you have Fault Codes/Information in your JBE (Junction Box Electronics) Fault Memory. I would FIRST
read all Fault Codes or Freeze Frame Data (Fault Details) in JBE Module, as well as the IHKA module which signals the JBE.

If YOU have access to any Scan Tool or Diagnostic Software (INPA/ISTA), please provide Make/Model, & any JBE/IHKA Fault Codes.
George

[julianbos16]

Hi George,

firstly, thanks for your reply.

I checked for fault codes, but apart from some with the NoX sensors, there are no fault codes related to anything regarding the coolsystem. (Checked this with an OBD-II scanner)

This afternoon, the car was working fine. I had heat inside the cabin, and the working temperature was around ~95 degrees.

The problems seems to only occur when it’s around ~1-3 celsius outside.

I will try again tomorrow, and see what it does. I might just go for a thermostat replacement…

[gbalthrop]

Originally Posted by julianbos16

... I checked for fault codes, but apart from some with the NoX sensors, there are no fault codes related to anything regarding the coolsystem. (Checked this with an OBD-II scanner)...I might just go for a thermostat replacement…

Please look & see if your 318i has a Water Valve & Auxiliary Pump, located below the Left Strut Tower under the hood, as shown in the First ISTA ScreenPrint attached in my prior post.

The JBE Fault Codes CANNOT be read with an OBD II Scan Tool. A "P-Code Reader" only reads faults in Engine Control Module (DME). This system is related to IHKA (Climate Control) Functions, so Fault Codes would be in IHKA or JBE Modules, NOT related to Engine Cooling (DME).

I see NO indication that your Engine Thermostat has any issue. That is basically a mechanical T-Stat with a bulb heater to open SOONER than normal in certain operating conditions. If a T-Stat fails mechanically, it usually sticks OPEN, causing engine to run cooler than usual. If the Bulb Heater circuit fails, that will set a P-Code, such as P0128, or P0597.

In US, large parts Retailers will read Fault Codes (Hexadecimal Codes) in Modules other than DME for FREE. If you can get codes read in IHKA & JBE Modules, that would be "Clues" as to cause of your issue. Fault Details show mileage & Number of instances of a particular fault.
George