Sorry to be a Cynic..
But I can see the "source" of my loss being discovered 10/25/23..
The day after my CPO ends..!

I called Blackstone tdy who advised they are 8-10 business days out on sample analysis.

They got mine 10/27 so I'll post results once received.

Happy 🎃

 

3.0 SC AJ126 340 HP
Maybe somebody has the knowledge about correct coolant temperature at the radiator outlet when the car is moving?

Did some OBD2 logging and in my case at 80 MPH highway cruise and 80F ambient temp. the values are:
220 - 230 at the engine block
190 - 200 at the radiator output.

After some overtaking and maintaining circa 100 MPH the engine block temperature reaches after some minutes 245 and amber warning "Engine temperature High" is displayed. Turning on the heater and taking foot of the accelerator drops the temps almost immediately to 225 - 230. At idle and city cruising system keeps bearable 220 - 225 even with A/C, fans are working.

Parts already replaced: thermostat, water pump, coolant, reservoir cap. Radiator flushed with vinegar, fins cleaned and partially straightened.
Did the Chemical Head gasket test and it kept the blue colour. System was tested with 15 psi and no leaks. Air bled while car was on a incline + 3 heat/cooling cycles.
I am slowly going crazy with this car, on BMW forums where they have a similar operating temp/high pressure coolant system I have read that on a moving car the radiator cools the fluid to 130 - 150 F. Next thing is to clean the supercharger cooler / AC condenser as they may block the air flow.

 

Shooting in the dark but faulty temp sensor (tells ts to stay closed when acting up/under vibration) or potentially DOA waterpump if you can verify ts is opening at temp.

 

There are two temp. sensors and both of them show correct values (ambient temp.) when the car is sitting whole night. They also give steady readouts while in operating temperatures. Water pump was replaced by myself and checked by putting a transparent hose on the overflow pipe, coolant flow was sufficient at idle and with linear increase corresponding to engine revs.
Thermostat was also replaced with a OEM part and is opening at 212 - 220 as the workshop manual states, which also confirms that the temperature sensors are giving correct readouts. What I cannot test is the full opening of thermostat. It is enclosed in a plastic housing, so without destroying the thermostat assembly how one can tell? Other option is to buy some brass piping and fittings to bypass the thermostat

 

I have replaced everything coolant related on this car already, did find a small leak at the water pump fitting. Wasn’t loosing coolant so don’t know how long it had been there. Tried bleeding system but don’t think I’m doing it correct

 

Just finishing up replacing the crossover tube w/ aftermarket aluminum ones. Both ends were sheared T the o-ring. Glad I got on it as this could have been a blown engine. I also found it had been leaking at the throttle body. That line that goes under supercharger connect to the back coolant pipe (on top and reasonable to get at) is now re-routwd around the drivers side to connect to the middle tube to expansion tank. Really despise all the little tubeunnning everywhere with those damn quick connect pieces of s*it that break and replacements aren't available and because it is hard plastic no alternatives allow anyone to fix it reasonably. That teeny tiny lock that holds the little elbow into the thermostat line is ridiculous.
yeah I'm still sore from cuts and bruises from the job. I will spare everyone about the symposer bracket unless some one wants to know.

 

I replaced those parts with OEM upgrades about a year and a half ago. I wish there were more aftermarket aluminum options available back then because the prices for the kits I've been seeing lately are great. I didn't do the job myself, but I also had to replace the symposer, as it was causing a nasty vacuum leak.

 

At 88F outside, 70 - 100 MPH with AC on, radiator outlet temperature was 105 to 140 F while cylinder head outlet was kept at around 205 F

Turns out that my problem was a clogged radiator. Flushing with vinegar or prestone stuff was not sufficient. New radiator fixed the issue.

 

tizzy, I finally got answer as to how the water pump brass fitting is assembled. Being an engineer I won't stop looking till I find an answer. Well I finally found a pictorial on the McMaster -Carr website that shows what that thing is all about. Here is a picture for everyone who may be interested.

McMaster-Carr drill and insert quick connect.