So the water pump on my 525i n52b25 recently failed on my way home.
Got the yellow warning and turned the engine off.

I have now changed the waterpump and thermostat and fully bleed the system about 6 times just to be sure.
I put in 50/50 bmw coolant and destilled water as recommended.

I still experience overheating issues, the car doesn't consume any water or mix water with oil or oil with water.
Cant find any leaks and it doesn't have any excessive pressure in the expansion tank.

the car acts as if the thermostat does not open until 117 degrees celsius when the fan kicks on high.
it can sit and idle and go from 103 to 114 and back down to 103.
as soon as i drive it without having the heater on it overheats, it also depens on the outside temp how fast it overheats.

do you guys have any ideas ? The issue is making me bald 😔

 

What makes you think that the engine is overheating? Does the yellow light come on? Or do you think that 117 celsius is a sign of overheating?

 

It does give me the yellow warning if i'm driving without blasting the heat.
but at idle it just goes up to 117 fans kicks in, it goes down to 103 then stays between 114 and 103 Celsius

 

Usually when driving the temperature goes down, due to the additional air going through the radiator. Look for debris in the radiator, usually the front. It might be clogged with leaves and stuff, impeding the air flow.

 

that was my thought aswell.
i have already checked for debris and couldn't find any.
im starting to think maybe its a clogged radiator or something.

 

Did you flush the cooling system when you replaced the pump and thermostat? What was the state of the flush? It is very possible that you do have a clogged radiator.

 

i honestly didn't flush it, was in a bit of a hurry to get it drivable.
but the color of the fluid i drained looked kinda like it hadn't been changed for 8+ years or so.

 

I also have a 2004 BMW 525i, I was wondering if anyone knows a good link explaining how to flush my radiator?

 

Google YouTube "E60 radiator flush". Lots of video explanations pop up.

 

Hi there, may I ask if your issue has been fixed? Because I've an E60 525i n52 and has the exact same problem as yours. New thermostat and water pump, everything else is old and stock. Flushed coolant, done bleeding probably 3-4 times and the issue is still there. Could a bad Coolant Temperature Sensor be the cause of it? Because I was wondering why my fan will not kick in with the Coolant Temperature Sensor disconnected.