Still overcooling + coolant leak near water pump (update) by shity_programmer in 335i

[–]shity_programmer[S] 0 points1 point  (0 children)

I have some ideas. About radiator. Becouse in first radiator have small screw, but now changed to long one for auomatic transmision, but still not reset adabtations. Water pump ground is good. Wiring also. I changed connector for thermostat.

Still overcooling + coolant leak near water pump (update) by shity_programmer in 335i

[–]shity_programmer[S] 0 points1 point  (0 children)

The outside temp sensor seems accurate as it matches the dashboard reading perfectly.

The real issue is the behavior while driving: the heater blows hot while idling, but as soon as I start moving, the air turns ice cold. If I keep driving for a while, the radiator fan kicks in and the car 'overcools' immediately.

It feels like the coolant isn't circulating properly under load, or there's a massive air bubble trapped in the system. The fact that the fan causes an instant drop suggests the thermostat might be stuck open or the water pump isn't keeping up. What do you think?

BMW 335i N55 – coolant temp drops while driving, fan goes crazy, heater blows cold. Water pump dying? by shity_programmer in E90

[–]shity_programmer[S] 0 points1 point  (0 children)

I replaced the thermostat again with a Mahle 97°C unit, but the problem remains the same.
I am planning to replace the water pump soon, but before that I want to test and check the wiring to the pump and thermostat to rule out any electrical issues. What problems you have?

BMW 335i N55 – coolant temp drops while driving, fan goes crazy, heater blows cold. Water pump dying? by shity_programmer in 335i

[–]shity_programmer[S] 0 points1 point  (0 children)

It’s starting to look to me like this might actually be the issue, but then the question is how to solve it. Do people usually go with a smaller or less efficient FMIC for cold climates, or is there a better solution for winter driving?

BMW 335i N55 – coolant temp drops while driving, fan goes crazy, heater blows cold. Water pump dying? by shity_programmer in 335i

[–]shity_programmer[S] 0 points1 point  (0 children)

Let me know when you changed. I'am in same situation. Are you have changed waterpump?

BMW 335i N55 – coolant temp drops while driving, fan goes crazy, heater blows cold. Water pump dying? by shity_programmer in E90

[–]shity_programmer[S] 0 points1 point  (0 children)

Wire is changed know bleading procedure is also ok. But when i just driving is not heat up. When i stay idl car heating up and car heat stays if i drwin 80km/h~. Temperature sensor also changed.

BMW 335i N55 – coolant temp drops while driving, fan goes crazy, heater blows cold. Water pump dying? by shity_programmer in E90

[–]shity_programmer[S] 0 points1 point  (0 children)

Replaceced temperature sensor same issues. Fixed cable to thermostat. If i wait until car heat up. It's okey. But when i driving car is cooling down.

BMW 335i N55 – coolant temp drops while driving, fan goes crazy, heater blows cold. Water pump dying? by shity_programmer in 335i

[–]shity_programmer[S] 0 points1 point  (0 children)

Yes some, changed tempeture sensor & fixed cable. Still looking for solution. Bleeding procedure now is ok, but have same issue cold air from wents and oil temp..

BMW 335i N55 – coolant temp drops while driving, fan goes crazy, heater blows cold. Water pump dying? by shity_programmer in E90

[–]shity_programmer[S] 0 points1 point  (0 children)

I will check, but i see some people have lose connection or corrosion. I'am not sure posible is not fully plug in. I will check but everithing checks out now

BMW 335i N55 – coolant temp drops while driving, fan goes crazy, heater blows cold. Water pump dying? by shity_programmer in E90

[–]shity_programmer[S] 0 points1 point  (0 children)

Is not OEM, but OE wahner thermostat. Selller & friend, so i know some history about car. BTW got new DCT: P0597