HELP! My ‘06 z4 3.0si got hot today… questions

[Jeff_Zeeee’23]

So I had been out running errands today. Outside temps around 34 degrees. Was at a red light and then it turned green and I noticed the acceleration was a bit slower than normal. Looked at gauges and temp gauge was in the red and the little red dot light was illuminated. No flash, no beeping. Pulled into gas station, opened hood. No steam, no leaks. I didnt check the expansion tank level (dooh!). I let it sit for about 20 minutes. Turned it back on and drive less than a mile to my local BMW dealer. Temp stayed in the 12 o’clock position for that short trip. Don’t know if it was still in limp mode or not since I was keeping my RPMs low.
Lucky for me I was so close to my dealer, and I was already scheduled for an appointment with them for tomorrow to address the open PCV recall.
Questions are since I am do new to the e85 platform :
- Does the red light flash when it is way hotter?
- Is there an audible alert at some point?
- Is the limited acceleration part of the ECU limp mode?
- I really don’t know how long it was in the red, but didn’t notice any difference in engine behavior until I took off from the stoplight… what are the chances of damage to the engine?

I have replaced the similar pump on my N20 based engines in the past (not hard at all) so not looking forward to big $ paid to the dealership knowing i can get the parts so much cheaper and do it myself… but it is already there so.

Anyway, wanted to pick your expert brains on the topic.

I plan to have them replace the pump, thermostat assembly, and mount an aluminum coolant flange fitting that I already have (part is by Rein and eliminates the plastic OEM part that is prone to failure).

[Jeff_Zeeee’23]

Oh, and the fan was really working hard before I turned the car off when I first pulled over. So the fan is operating.

[Jeff_Zeeee’23]

Replacing this old pump was on the list to do next but I only have had the car 2 weeks. Just finished replacing the front struts and did an alignment yesterday.

[smorris_12]

I was about to pour scorn on you for the hardship of dealing with a temperature of 34, until I spotted references to gas stations and realised you meant farenheit and not Celsius!

BMW temperature gauges have about 5 positions rather than being linear (stone cold, warming up, normal, bit hot, too bloody hot.) I think the red light flashes on the last one to get your attention.

The ECU will reign in performance to avoid throing fuel on the fire so if it drives ok again cold you probably don't have too much to worry about.

[Jeff_Zeeee’23]

Thank goodness! Looks like I just went into the “bit hot” range.

Heartburn time on part pricing:
Water pump from dealer is $650.
Online Retail price for BMW part is $550.
Pierburg (OE) part is $283 online.

[Mr Tidy]

That experience is exactly what happened to me when my first Z4 had the water pump die, including going into limp mode.

If you want to be absolutely certain there should be error code(s) stored in the diagnostics.

[Jeff_Zeeee’23]

So I got it back from the dealer today. Stored code for pump malfunction 3 times which makes sense. Failed while driving. Turned off. Restart, drive to dealer, turn off. Turn on to move it to the bay.
All said and done, it was about $1600 for the pump, thermostat replacement. And that was after my 10% off parts discount for being a BMW CCA member.