[bonestockE36]

I forgot to mention I re-did that test and pushed it up to 18psi. The gauge immediately starts decreasing, but slows as it gets closer to around the 9psi mark, where it will then hold around the 9-10psi mark.

It's hard to say if I'm getting a reliable reading, but I tried it quite a few times and got this same result.

Now look for the coolant the air displaced, probably in a cylinder.

 

[bonestockE36]

Good for you, but there are some people had no luck and continued to have overheating and no cabin heat after doing this way.

If temperature is out of the blue and there is no cabin heat, you know something is wrong. Who continues after observing no cabin heat?

So why does filling coolant go wrong for so many? I have never had trouble, never jacked the front of the car, never dumped half a gallon of coolant on the ground "bleeding". Even side of the road repairs (both were E36, 1 blown ET and one radiator neck). I just did a water pump, put everything I drained back in, ran it for maybe a minute, called it done. Topped off in the morning.

What is the actual cause of these problems? My guess is rushing the fill entraining a lot of air, not waiting for air to come out, or sticky heater valves/blocked cores. What else could it be?

 

[bonestockE36]

If it was a common failure there would have been more in 4 years.

How does one remove the impeller scraps in the cooling system?