Author Topic: Do I need to drain a block? (Read 3142 times)

DarioM42 · « **on:** January 05, 2011, 03:16:56 AM »

I want to change coolant in my E30 M42B18, do I need to drain a block (to unbolt block drain plug), or can I just drain it with disconnecting hose between radioator and block?

thanks

Hodge · « **Reply #1 on:** January 05, 2011, 07:34:53 AM »

You don't HAVE to. I never have. Most people never do. If you undo the radiator drain, undo the hoses to the thermostat housing, it should get pretty much all of it anyway. I just did my coolant on my E36 M42, and it looks perfectly clean, and stays quite cool.

DesktopDave · « **Reply #2 on:** January 05, 2011, 08:14:32 AM »

I do them all & flush them too. I pull the heater core hoses, the block drain on the rear passenger side, and both hoses. I just like to do a complete job...though it's a bit retentive.

Not draining the entire system will make it easier to bleed. Keep in mind that coolant contains chemicals to resist corrosion in the system. The more fresh coolant you have, the longer you can go between changes.

DarioM42 · « **Reply #3 on:** January 05, 2011, 01:46:55 PM »

Thanks for the info guys!
Hodge, how much coolant roughly you put in when you don't drain block?
Full system is cca. 6.5 litres / 1.7 gallons.

DesktopDave · « **Reply #4 on:** January 05, 2011, 04:19:09 PM »

I've often used more than two gallons to refill my e30 (sorry I'm not directly answering your question) but I'm pretty sloppy with flushing the car out.

BTW, it's far easier to bleed the car when you cut the coolant amount. 50/50 is to thick IMHO. I usually mix a gallon of Zerex G05 or BMW coolant with two gallons of distilled water and half a bottle of water wetter. The thinner 33/66 mix makes it very easy to bleed and might cut down on water pump cavitation & drag. I park my car outside & drive it often, never had a problem with low temperatures. It typically gets down to 0degF here, frequently we're in single digits.

Hodge · « **Reply #5 on:** January 05, 2011, 07:59:11 PM »

I put probably 2 gallons in mine when I put it in. Mind you, this time, I also changed the water pump, and a tub full came out of the pump recess (yes, I did full drain the radiator and hoses first).

I used one full bottle of water wetter, then a full gallon of distilled water, and then over 3/4 of another gallon of distilled water as well. It did bleed quite easy.

When the temps a few weeks back here were in the 40's-60's, my temp gauge barely reached the 1/4 mark, and only straight up when idling for extended periods (at lights, etc), then it would go back down as soon as I started again. I know my thermostat isn't stuck open either, because my temp gauge would always reach straight up before I did the coolant flush.