best coolant for d24?
 

First of all hi everyone, glad i could finally join this forum. Recently I bought a 740 with a D24.

The car has been a bit neglected and eventually im gonna change all the engine seals and all fluids.

Long story short, I would like to start with a coolant change. What antifreeze do you guys use to mix coolant for your D24?

Hi, and welcome to the forum. :)

I have been using old school green basic antifreeze mixed 50/50. Not seeing any corrosion problems. I think the key is to change it every two years.

Since we're talking fluids, more important probably is to run full synthetic motor oil.

Power steering seems to like basic Dexron ATF, not power steering fluid.

What transmission do you have?

I have seen a lot of people say full synthetic oil is a must for these engines so thats definetely the type of oil that im considering. I believe my trans is the M46 -4spd with OD.

M46/OD gets ATF Type F.

I'm not sure if it's the "best," but for coolant, I run Zerex G05

Other fluids I am currently running....
Motor Oil: Mobil 1 0w-40 European FS
M46 Transmission & Power Steering: Redline Racing ATF (Type F)
Rear Differential: Amsoil Severe Gear 75W-90

I will make another vote for Zerex G-05, similar to the above, not necessarily that it is the "best" but certainly it is good enough for these engines that are not particularly demanding as long as coolant is correct mix and kept clean, as ngoma said. To my mind the advantages of the Zerex are that it has some extended life properties (relative to old style green coolant that should be changed every couple years), has wide compatibility with other coolants in case someone accidentally adds something different, and is widely available at almost any parts house.

I think an argument could be made for various other antifreeze products out there (there are MANY, some of which promise extra long life, etc) but the real bottom line is just to use something you know you can get your hands on reliably and are comfortable with, meets the requirements, and is kept clean and uncontaminated with other fluids or incompatible antifreeze types.

On that point, if you are changing from another type of antifreeze, be sure to flush thoroughly with distilled water to remove all the old liquid, including from the radiator, heater core, and oil cooler if equipped. There is no dedicated drain point on the engine block, so best block draining is accomplished by removing the thermostat housing and flushing thoroughly from there.