[markhamr]

I had backpacked my initial issues in another similar thread, but there's a few people doing the same and my issues have gotten more specific, so I'm making a new thread to avoid confusing different people's issues. That thread does have a lot of good info posted for reference though.

Original breakdown:

I got a yellow warning (the third time in a week), pulled over, checked the coolant reservoir and it was pressurized (hot water spewed/sizzled out when opened slowly). I waited a few minutes, drove again slowly and quickly got the yellow then red light, so I had it towed home.

Diagnostic steps (a few days after getting towed):

A. Hooked up Schwaben scan tool - ran full code scan. Only relevant code (for Engine-DME Motor Electronics group) was 378F: BSD message Electric coolant pump missing. All the other codes were for other CAS, ABS, etc and seemed to revolve around communication (most referring K-CAN). I found a the attached PDF of N55 diagnostic fault codes. I've included a screenshot of the section related to my error code.

B. Coolant bleed procedure - i ran this for 5 minutes and the water pump consistently turned on / increased speed / turned off. I opened coolant reservoir and saw coolant coming in consistently with speed of pump. Ran full code scan again and didn't find anything knew.

C. Radiator fan test - i turned the car on with full AC and it quickly got very cold. Ran the car for about 5 minutes and coolant temperature increased from 120 degrees (measured a minute or two after starting) and was 200 when i turned off the car. It then slowly decreased as expected.

Questions:

1. Is anyone able to make sense of the diagnostic information below related to my code? It seems that it is indicating that it is a communication issue with the pump.

2. How do I go about further diagnosing if it's a communication issue or if it's perhaps the waterpump failing and thus not communicating properly?

3. What part would have to be replaced if it's an electric issue? I looked over realoem for the water pump and throughout the other component sections and could not figure out what electric components could have gone wrong / might need to be replaced.

Any help would be great as I should be receiving the water pump kit (pump, thermostat, bolts, coolant) today from FCP Euro and was planning on installing on Saturday with a friend's hoist, but don't want to necessarily due that if the pump is still good and if installing a new pump won't fix the communication issue. Also, I'm considering replacing the hose between the pump and thermostat as well as any others that are nearby if people strongly advise? I would need to see if a local shop could quickly get from local warehouses in order to get them in time for repairing on Saturday.

[MIBMW]

Were you able to visually look at the water pump when it was running?

My WP is leaking between the aluminum and plastic part of the pump, car is not throwing any codes but leaking like a sieve.

[markhamr]

I did not look at the pump, but my coolant level was right around max and I haven't added anything to it since I bought the car a few months. So I would think it's safe to assume that there is no issue with leaking, but let me know if you think otherwise.

[markhamr]

Here is the full list of errors that came up on INPA (Bimmergeeks version). After researching, I'm getting concerned with the CAN errors.

On a side note, is there a PC software that gives more info on each error code? Did i download the wrong version of INPA or not using it properly?

[simplesilver]

Looks like your water pump may be failing or the electrical connection on the pump may have an issue. My car overheated on the highway just last year. When I got it towed home I put my scanner and had a fault code right away about communication for the water pump. Then I could go further and see the pump rpm's. After idling for a couple minutes and temp rising there was zero rpm. Did the pump, thermostat and hose the next day and all has been good since... My car is a '07 328i with 233k km now...

[markhamr]

Originally Posted by simplesilver

Looks like your water pump may be failing or the electrical connection on the pump may have an issue. My car overheated on the highway just last year. When I got it towed home I put my scanner and had a fault code right away about communication for the water pump. Then I could go further and see the pump rpm's. After idling for a couple minutes and temp rising there was zero rpm. Did the pump, thermostat and hose the next day and all has been good since... My car is a '07 328i with 233k km now...

Thanks for the post. That makes sense about the electrical connection on the pump. My buddy with the lift bailed on me for today and so given that he won't be available for another two weekends, I'm likely taking it to the indy this week and gonna have to cough up to the labor bill.

In the meantime, I'm still trying to research to see what I can find/learn. I sucessfully installed ISTA+ last night, which is much more helpful than the Schwaben scan tool!

Below are screenshots of the error log, test plan, and the water pump error description/details/test procedures. Attached are PDFs of the detail related to the other errors that happened at the current mileage of 120,504 kilometers (2. RDC K-CAN, 3. Combox). Based on these errors and there doesn't appear to be a pervasive electrical/communication, it seems like it may just in fact be the pump.