How much coolant should radiator take?

[mc625569]

I’m flushing coolant on my 87 325e after a water pump change.
When i drained coolant I got just under 8 liters which I understand to be low. I have no visible coolant leaks.

When I refilled it also took just under 8 liters . I had heater on when I refilled.

Any idea why I’m not taking more coolant ? Could my ancient radiator not be taking the full volume ? I got just under 2 liters in the radiator alone.

I refrained and filled again filling radiator and block separately and still had same issue.

I’ve been driving the car and it doesn’t seem to overheat.

What am I doing wrong, this is my first coolant flush.

[Echo30V]

WHat is the level in the expansion tank when the car is cold?

[ThatOneEuroE30]

How much coolant should radiator take?

Your not getting all the coolant out.You still have coolant in the heater core and will still have some coolant in the block unless you knock out freeze plugs.

[mc625569]

Expansion tank level is up to full line when cold.

How do I drain the coolant from the heater core? I’ve just been draining via radiator petcock and removing drain plug in the engine block and waiting a while.

[Echo30V]

I did not know that changing coolant on the M20 involved popping out the freeze plugs on the block. I never do that, is that necessary? I always thought that draining the radiator and removing the drain plug on the block was sufficient.

[e30davie]

I wouldn't touch a freeze plug unless it was leaking or i was completely rebuilding the block on the work bench.

I think you are completeley over thinking this coolant flush, just get out as much as you can by popping off the bottom radiator hose, and fill it back up with new stuff until its full.

If you manage to replace 90% of it that's pretty good. Its not like that last 10% of "bad" coolant is going to destroy your engine. it will all mix in together and all will be good.

[ThatOneEuroE30]

I wouldn't touch a freeze plug unless it was leaking or i was completely rebuilding the block on the work bench.

I think you are completeley over thinking this coolant flush, just get out as much as you can by popping off the bottom radiator hose, and fill it back up with new stuff until its full.

If you manage to replace 90% of it that's pretty good. Its not like that last 10% of "bad" coolant is going to destroy your engine. it will all mix in together and all will be good.

Exactly. I should have added i don’t recommend knocking out plugs. How ever that is only way to ever last drop out.

[Echo30V]

Knocking out freeze plugs turns a coolant flush into a big ass job.

[MrBurgundy]

What I do for a good coolant flush is; drain the car from the radiator plug, then fill it up with distilled water. I'll keep running water through it until there almost no coolant present in the water as I drain it. Then I add coolant after. That's the best way to get most of the old crap out without knocking out the plugs.

[jeffnhiscars]

The reason coolant changes are recommended every 2 years is to refresh the corrosion inhibitors. I'm sure adding 80-90% of a total fill up will more than serve that purpose.