1998 BMW Coolant Change Recommendations

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To give some context...

I realized this year that I cannot recall exactly when the coolant was changed last on my '98 BMW 328is. This spring it would occasionally start to overheat and I figured out the issue was down to the system being a bit low on coolant. At the time I added approx. 30-40oz (didn't seem like much) of some filtered tap water, bled the system, and it has been running great since.

I would like to get the old coolant / bit of tap water out of there before it is stored in an un-heated garage during the upcoming Michigan winter. The coolant visually appears fine and is a greenish-amber color. The car has always been serviced by the dealer, myself, or an indie shop that specializes in BMWs so even if it isn't the OE blue coolant I am assuming it was something that met similar specs.

Other than being a bit low earlier I haven't experienced any coolant-related issues.

My plan is to....

just drain the radiator, refill, and bleed the system. I figured this might be the safest bet to not "shock" the system and a full flush might not be necessary since I'm not trying to "fix" anything. Next spring I would do a greater overhaul replacing the expansion tank and coolant hoses and then refill with more fresh coolant.

Am I wrong in this approach? What coolant would be best, especially since it will have to mix with whatever doesn't drain out of the block / heater core? I am leaning towards the BMW blue stuff, but it looks like Zerex G-05 is recommended on some forums for BMWs. I would be open to the Zerex and any other aftermarket options if there's a compelling reason to use it instead (like it might play nicer with mixing).
 
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I have a 98 328i also. I just run Prestone and distilled water. Recommend by my BMW mechanic. Been running it since a top end rebuild around 50k miles ago. Coolant has been the least of my problems. Usually things in the cooling system break before the coolant is in there too long.
 
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I also recommend sticking with the OEM BMW coolant or any of the applicable products sold at the local auto parts stores marketed specifically for that application. As mentioned, it's sold as European "blue" coolant, VW G-11, BMW OEM, or Glysantin G-48. My local BMW dealer charges $22 for a gallon of concentrate and what you get at most auto parts stores are pre-mixed at 50/50 so it's actually a bit cheaper to just get it at the dealership. I think full price is $26 a gallon at the BMW dealership so even at that price it's cheaper than Autozone. Add a gallon of distilled water from the grocery store for $.89 and you have two gallons of "ready to use" coolant.

BMW suggests a replacement interval of every four years.
 
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To me, anything that's worth doing, I try to do properly. I'm not talking but an elaborate OCD multi-step flush, but I'd at least drain the block as well.

The cooling system holds ~11 quarts. Draining just the radiator is going to leave a large proportion of the old, unknown coolant in the system, and reduce the effectiveness of new coolant added to it. Radiators, expansion tanks, water pumps, and thermostats may be easy to reach and replace. 23-year old heater cores are not, so I try to treat them as nicely as possible.

The block drain is at the rear, adjacent to the O2 sensor, which partially obscures it, but is otherwise not that hard to reach, as long as the front end is lifted. But it does have a crush washer, and a raincoat is advised. Set the heater controls of full hot to open those valves.

NAPA carries G48 full concentrate. It's on special this month. Some stores also choose to carry the OE branded jugs of BMW and MB coolant. G-05 is a very similar HOAT coolant, and more widely available, so some use it as an alternative.

It's easy, and tempting to choose the easier path. I've been there. But it's a slippery slope, and one that German cars don't tolerate well, and the consequences may manifest themselves in an unpleasant and expensive fashion later on.
 
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I also recommend sticking with the OEM BMW coolant or any of the applicable products sold at the local auto parts stores marketed specifically for that application. As mentioned, it's sold as European "blue" coolant, VW G-11, BMW OEM, or Glysantin G-48. My local BMW dealer charges $22 for a gallon of concentrate and what you get at most auto parts stores are pre-mixed at 50/50 so it's actually a bit cheaper to just get it at the dealership. I think full price is $26 a gallon at the BMW dealership so even at that price it's cheaper than Autozone. Add a gallon of distilled water from the grocery store for $.89 and you have two gallons of "ready to use" coolant.

BMW suggests a replacement interval of every four years.
+1

I use the BMW coolant in my E90 and other BMWs I service. It's actually cheaper to buy the concentrated BMW coolant and then some distilled water than whatever they are selling at Autozone that might be compatible. I think the last time I bought BMW coolant I got it from Amazon, or from a dealer selling it on ebay. It was cheaper than buying the coolant for my Wrangler.
 

cutlassvillager

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Thanks everyone! I'll plan to go with the BMW stuff and will take a look at the access to the block drain and probably end up draining that too. Any idea on the size of the crush washer?
 

cutlassvillager

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Thanks for the real OEM post! I used that crush washer part number at the dealer when picking up the coolant. The process of draining the block was very messy, but easier than I had anticipated so I appreciate the suggestions to just do it right. I think (but am not certain) a VERY small leaf might have fallen in the coolant while refilling (thanks to the fall weather), but it was so very small I'm hoping that's negligible. The old coolant was a dark-ish amber, so I feel better getting that unknown combo out of there!
 
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Re: messy block drain...

On my 1998 528i (M52 engine) I recall that the block drain dumped coolant all over the suspension and subframe and it could run everywhere. I had a system where I had a short piece of clear tubing 1" or 1.5" diameter. I would route it around the suspension, into a bucket and near the block drain. From above I had the tubing held in my pinky and turned out the drain bolt the last couple of threads with my thumb and forefinger. As soon as it let go I shoved the tubing against the block. The bolt and all the coolant went down the tube into the bucket with nearly no mess. For whatever reason I was just thinking of this yesterday...
 
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Yeah, draining the block is a mess, but it's just one of those things you learn to deal with. Haven't felt enough desire to concoct a more elegant solution, other than loosening the plug and holding it against the opening to allow it to stream out in a somewhat controlled manner (but still stream down your arm), rather than having it gush out and douse everything, including you (hence the "raincost" mention above).

At least spalshed coolant is a lot more benign than oil, which leaves a real mess.
 
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