[Anthony0101]

Hello, I have e90 325i 2005 with the 2.5 litre variant.


For quite some time I've been dealing with an obnoxious problem.

Sometimes the engine overheats, there is yellow temp warning light, rarely the red one and the heater blows cold air. Obd shows around 120deg C. Then, after like 5 minutes, the temp drops to ~ 90 degrees, and it starts blowing hot air. Sometimes, it ceases with one overheat and after thar it starts blowing hot air and I can drive for hundreds of miles without any problems. This usually happens after cold start and driving a little.

However sometimes, the sequence repeats for like 5 times in a row: it overheats, starts blowing hot air, ok for 5 mins, then overheats again + cold air and so on.

Also, there were weeks in between where I had no problems at all.

I believe it may be something with thermostat, it stucks closed..?maybe some electrical issue, wire/ecu?
As the thermostat itself is a new one, replaced few months ago.
Checked the fan, works fine.
BMW specific software shows no related codes.

I am completely lost, been to multiple workshop services, they are unable/unwilling to find the problem and suggests it's blown head gasket. But I doubt as leakdown test was done and it is negative, also the problem has been persisting for like 3 months and the engine would have been fked up by now lol.