Quote:
Originally Posted by Surly73
I like that common sense is on the list of required items 
A weakness that I see in this process is the fluid in the radiator loop. The coolant system isn't a single loop, there are branches all over the place and one of these is the entire radiator. The thermostat needs to be open to ensure you've got proper flow here.
With every inline 6 BMW I've worked on, (M52, M52TU, M54, N52, N55) I have found that even in the summer heat when it's just idling and I have the hood up it sheds enough heat to the environment that the thermostat doesn't even necessarily open. (stop and go traffic in the blazing sun with the AC on is a different environment than idling in the shade in my garage with everything off and the hood open). On the N series engines with electric water pump, if the weather is cool the pump might not even run!
So - I can't conclude your method won't work or anything like that, but it would be a serious reservation on my part. Now - I would assume that the fancy-pants BMW bleed program would force the thermostat open. I wonder if your method would work better if you just connected a charger/power supply and used the bleed program to circulate instead of running the engine? Less risk of burns etc... too.
Related - for a couple of decades I've always tried to change fluids more often than manufacturer recommended. Often with fluids anywhere in the driveline (brakes, transmission, clutch, steering) I can observe improvements in the system after changing the fluid even when I do it "too often". One advantage of doing this is that one doesn't need to feel desperate to get ALL of the old fluid out. When I use a turkey baster to extract and replace all of the power steering fluid once per year or every other oil change or whatever, I don't need to get all stressed about removing every drop of it. What was left in the system is still "good enough" and will blend with the fresh fluid. Same for coolant, transmission, you name it. Taking this approach often means it's an easier job to do (e.g. turkey baster power steering reservoir and then refill instead of pulling banjo bolts at the rack to get every drop out)
Now - you found what appeared to be incorrect fluid so what I just said doesn't apply 
Thank you for devising and posting and innovative way of performing this job, which BMW really made a PITA on the F10 by eliminating some drains and requiring a vacuum apparatus to refill. |
You make very good points regarding that there are multiples loops. I was under the assumption that the thermostat would open up once the car was getting up to temp or whatever. I drained out about 10 gallons of old coolant and antifreeze total so if what you say is true I'm sure I got multiple systems flushed. I also ran the bleed procedure to monitor the content of the fluids color and it all seemed to be blue. I will keep your advice in mind next time. The reason I have this fluid flush mentality is because I don't know what the previous owner put in the car. It bought it at 100k and when doing the valve cover gasket we found out he was using conventional oil. With this and the coolant being green I decided that this previous owner didn't know what he was doing and thus I needed to get as much old fluid out while I can.