removing knock sensor of BRM

Guys,

I would likt to drain my coolant out of the block completly, but I found the knock sensor very very tight and I´m worried about snapping it off or break the thread......Is everyone experienced in doing that?

I don´t know how much coolant remains within the block when draining it just off the hoses. Last summer, I filled antifreeze with -13F rating in and yesterday, the engine overheated when my wife was driving (of course)....never have had troubles with the temperature, I guess it is the thermostat and removed it and checked the antifreeze, strangely it was just +4°F but now i would like to fill the system very carefully to eliminate every coincidences.  Can I drain the system by a short running when cold with removed water hoses to get out the sludge? Removing the knock sensors seems a bit risky.....

If you can't get the knock sensors off, drain the coolant then flush it with a garden hose. When the water comes out clear, it should be good enough. Take the time to backflush the heater core if you haven't already. If you did get the KS off, I guess your plan would be to use a garden hose anyway in the KS holes.

Make sure once you fill it back up that you bleed the system

Are you refilling with “full strength” antifreeze, i.e., not 50-50 mix?

I’ve drained my system a number of times, with out removing the knock sensors, and never had a problem getting plenty of anti-freeze back in to lower the freezing point to at least -30F. I always need to add additional water to fill the system.

If you remove the lower hose from the radiator, and jack the right side of the front end, it may help get a small amount of additional coolant from the radiator and hose.
Remove the heater hoses near the front of the engine, and back flush the heater with the garden hose, then drain the heater hoses as much as possible before reinstalling. If you then blow out the heater and lines, using low air pressure, you will get an additional small amount of water out.

I raise the front of the car about a foot or so, and open the bleeder (stuff a rag behind it to protect the OPTI), while slowly adding new coolant through the plastic tank. As soon as you see any fluid coming out of the bleeder, close it. Fill the tank to just above the divider, close it up and start the engine, and let it run for two minutes. Stop the engine, “crack the bleeder" a couple times, and you may get a little more air out. Restart the engine, let it run 2-3 minutes, and repeat the above.

Top off the coolant, and take the car for a ten minute drive, and let it cool off for a short time. Carefully loosen and remove the cap (it will have pressure on it), and top off the tank up to the divider.

Over the next couple of days of driving the system will purge itself of air, lowering the level in the tank, and allowing you to add additional water or antifreeze, as needed.

best to determine whether the car in question is a tbi or an LT1,.

The engine is an LT1. My intention to remove the knock sensors is now not to flush the system, it´s just to empty the system completly. I flushed the system summer very extensively with the garden hose when idling the engine. I removed the lower cooler hose, ran the engine and filled water into the tank regarding to balance the flow from the garden hose. I did so until fresh, clear water came out of the lower hose. Afterwards I filled the engine with antifreeze mixture rated to -13°F = -25°C and ran the engine without any troubles until my water cooler had to be destroyed because I couldn´t remove the oil cooler hose what is connected to the water cooler tank. The oil hose leaked and I wanted to replace it due to the risk of breaking. You have to remove it by using violence, there´s no possibility to resist the loosening torque of the screw connection and if it doesn´t comes loose, the oil cooler within the water cooler broke as anticipated and I had to replace the complete water cooler ( and could replace in turn the oil cooler hose as well)

Then I refilled the antifreeze again, maybe there remained a small amount of water within the block, I didn´t remove the knock sensors. I can´t hardly suggest that the overall antifreeze rating is influenced by the small amount of water with unknown antifreeze rating. Maybe I try to remove the water temperature sensor, I guess it´s located a bit underneath of the water pump and might be the deepest point to drain water except of the knock sensors. If I then fill a mixture of 50/50 water / antifreeze it should be ok.....

Bleeding the system is no problem and worked well without struggling the last times.

just use straight antifreeze,. no 50/50. add till you're happy with how strong it is,.

I use G05 Antifreeze, best for cast iron engines, as well with alloy heads.  I provided a 20 L barrel what is rated without mixing to -40° (at this Point, Fahrenheit and Celsius is equal).
But 40° is too much, the cooling effect is worse that with -13°F /-25°C. So I have to mix it up with water, but I can measure the rating. In Germany, temperature is
very rarely deeper that -13°F, and if so, the antifreeze won´t gelatinize immediately. In North Canada, I would overthink this statement....I use destilled water for the mixture, it protects the engine from buildiung up chalking deposits.

well it sounds like you are much more informed than me,.

carry on,...