My dad's BMW has an 'coolant light' which according to the manual tells us when the radiator is in need of more antifreeze/coolant..

There isn't a leak, but for some reason it needs to be refilled...

Its not empty, but is clearly not full...

question is, When adding antifreeze to a radiator, is it necessary to flush out the existing antifreeze? or is adding to it acceptable? --- for now until I get the chance to take it for maintenace at the dealer? (ie; next oil change)

 

It's fine to add antifreeze/coolant but not directly to the radiator. You add it to the recovery tank instead.

 

Preferably, do this after your car has cooled off. Also, run the heater every once in a while to circulate the water through that system as well.

I had a radiator replaced one time and the tech did not cycle the heater. Everything was fine in the summer but all my antifreeze disappeared the first time I turned on the heat...pretty scary when you're on the highway and your temp light comes on.

 

You don't need to flush anything out. Simply add coolant to the expansion tank and monitor the level for any leaks. If you're using BMW coolant, it's not pre-mixed, so make sure you mix half-half with DISTILLED water.

DO be careful in mixing different kinds of coolant. Most BMWs require (ok, HIGHLY recommend) BMW blue coolant. If that's what's in there, add more of the blue stuff. However, if it's green or red (which it shouldn't be), then you might want to flush it out and replace everything with BMW blue.

You shouldn't be using anything but BMW blue in your bimmer, but if you mix different kinds of antifreeze together, then certain types of corrosion and other bad things might happen.

 

With the rainbow of antifreezes on the market, explaining the differences between each one and why can take many pages.

I'll shorten this up to make it easy:

Japanese automakers use an organic acid technology based coolant, known as "OAT." This is near identical to GM's controversial Dexcool, but Japanese automakers also add a touch of phosphates as a means of supposed "instantaneous" protection. Euro automakers do not use phosphates as I assume that Europe has issues with hard water, and phosphates are not too friendly with that. Hence, when mixing antifreezes containing phosphates, use distilled water (when doing a complete flush, as you buy full strength), or use 50/50 premix from the dealer. This is the same reason why tap water is acceptable for "mixing" Dexcool or any silicate and phosphate free antifreeze, they are less suspectible to hard water. Instead, Europeans use a touch of silicates along with OAT to form a HOAT (Hybrid Organic Acid Technology) antifreeze. Both OAT and HOAT coolants are long-life coolants.

There are no OTC long-life coolants containing phosphates and no silicates. Personally, I think its a non-issue as the "straight OAT" coolants containing no phosphates or silicates do a fine job in most cooling systems. When flushed completely with plain water (several cycles), most cooling systems on the market can handle "straight OAT" coolants without issues. The only systems in question are the DC, Ford, and Euro manufacturers that require the HOAT coolants due to possible incompatibility problems with "straight OAT" (no phosphates or silicates) coolants, as DC and Ford had corrosion problems with OAT in their heater cores. Those three require the HOAT based coolants, which is commonly avaliable under the "Zerex G-05" brand at Pep Boys. When diluted 50/50, this stuff appears nearly clear.

Generally speaking, there are no compatibility problems with topping off with another coolant. The problems you run into are when you top-off an extended life system with conventional silicated coolant, which at that point, since you contaminated the system, you limited the service life of the system's coolant to 2-yr/30K. If you top-off an extended life system with another extended life coolant, there will be no harm done, though antifreezes work best when brands/chemistries are not mixed, somewhat like motor oil.

For top-off, go to any auto parts store and buy a 50/50 Premixed long-life coolant. Prestone makes their "All Makes/Models" "straight OAT" 5/150 coolant in that form. It is a very light green color. Supertech (Walmart) has a similar 5/150 formula but is reported to be gold as its produced by a different distributor.

 

awesome guys!!! thanks for the help! i really appreciate it!

I've decided to just make an appointment and take it in since i need the blue stuff anyway.

 

Dang... michael is like a fluid expert.

 

Great right-up and info.......

 

Great info. Thanks

If that's the short version, I don't think I wanna read the long version

 

My short version would be "go to Honda/Acura and buy the Type-2 antifreeze/coolant".

 

Johnny's version of KISS

 

JTso is just too lazy to mix it.

 

that would've been my response too.

i just bought a jug a couple of days ago...

 

Honda Type 2 is WAAAAAAAAAY too $$$$. $15.95+ per gallon.

I can premix my own Ext. Life Antifreeze for about $8/gal with tax. $6.88/gal Supertech Extended Life 5/150 + 1 gal of distilled water.