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Hey all,

New to the forum, but in need of help. I replaced the water pump on my 07 BMW 335xi. All has gone wrong.

For some backstory, this is my girlfriends car. She was driving along on a cold day and all of a sudden her heat stopped working. Then the engine started overheating. Seemed like the water pump was dead. I replaced the pump and the thermostat while I was on there.

Since then, the pump has not been functioning correctly. I cannot get the car to activate it's bleed procedure and at this point I've tried about 50 times. The car has an adequate battery charge. The car is plugged into a charger when trying.

After pulling the pump out again, I decided to bench test it. It works. 12V to the main leads and 12V to the PWM lead makes the pump run full out. I also bench tested the old thermostat to see if maybe that was her problem. It functions correctly. I had disassembled the old pump so I had no way to test it.

After bench testing, I tested the connector. 12V is on the main lead from the car when the pump should be running. All of this tells me there is a PWM problem. The connector was also replaced as it was chewed up pretty bad.

Narrowing that down some more is difficult as I don't understand BMW's PWM system. I have tested and replaced all of the fuses (this car is a garbage pile and was missing about half of the fuses). The under hood ECU/fuse box was also looked over. It is unlike most of the ones I have seen online, it only has a single 50A fuse and no spots for other fuses. Pic attached. That fuse was tested and it works. It was also replaced in case (with Hondas some fuses will test fine but not actually sustain current).

Getting down to it, pulling that 50A fuse that is under the hood and then replacing it (after any amount of time) causes the pump to turn on and run full out. It still will not bleed but it will not cause an overheating condition.

Has anyone ever had something like this before? What is the culprit? Any ideas on where to look and what to do? We have read about every single post that we could find about this and are coming up short. My girlfriend is very upset and almost irrational at this point, threatening to junk the whole car over this.

Aaron

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That water pump is probably covered under a class action that expires may 5, 2022 for N54/N55 engines in certain vehicles. I would call a dealer and see.
As to why it’s running constantly, I have no idea as it could be MANY things but I would have the vehicle professionally diagnosed by a dealer or BMW SPECIFIC Indy before even considering junking it
 

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I had a water pump failure while car was still on CPO warranty. Dealer replaced pump, radiator, coolant expansion tank (apparently it was a typical collateral damage related to the pump failure) and couple hoses - all covered by warranty.
I asked why haven't they replace thermostat at the same time - was told that they've tested it and it was good.
6 or 7 years passed and had to replace some hoses and radiator because of leaks (was loosing coolant) but no pump related issues.
 

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The E90 engine has a coolant control system which regulates engine temperature, based in part upon the load on the engine...max throttle highest performance engine temperature is different from low load engine 'loafing'...control of emissions vs. need for power is designed into the system, and the DME controls the flow rate of the pump.
 

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The E90 engine has a coolant control system which regulates engine temperature, based in part upon the load on the engine...max throttle highest performance engine temperature is different from low load engine 'loafing'...optimum temp for control of emissions vs. need for power is designed into the system, and the DME controls the flow rate of the pump.
 
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