Why are BMW Cooling Systems so Apoplectically Complicated?

Knurled. said:

Germany has yet to figure out how to make viable plastic or rubber.

______

Which shocks me, since I have been hearing about “german engineering”  since i was a kid 

Patrick said:

MTechnically said:

In reply to z31maniac :

Depends on the BMW in question. You can replace the entire cooling system (radiator, water pump, thermostat, idler pulley, hoses) for an M50 powered car for $400-450. If you are really worried about a failure you would do that every 60,000 miles. Do other cars have to deal with cooling system repairs as frequently, no, but the cost is less than $.01 per mile. Not exactly what I would call unreasonable cost, but I guess people have different ideas of what is reasonable.

It’s completely unreasonable to have to rebuild your cooling system every 60k.  This is the problem.  

Well said patrick

my hondas/toyotas have gone 200k miles before needing a new radiator. 

I have changed water pump on them at 100k miles, as preventative.  Never had one go bad on me 

60k cooling system rebuilds? Wow

In reply to mr2s2000elise :

As I already pointed out, that is a worst case scenario, that I used to illustrate cost is not that high when it comes to repairing these cars. Especially in the case of the cars a GRMer would most likely be looking at.

There are tons of people who get 100k out of water pumps and 200k, especially if you are willing to replace an end tank, out of a radiator. As with any car the biggest factor is how the car is actually used. Cars that see more highway miles and longer trips are less likely to issues than cars that do many short trips and heat cycle more often. I'd only recommend that someone do a 60,000 cooling system overhaul of they were buying a used car and had no idea about the service history and use of the car.

Rslifkin pointed out, BMW's do tend to run higher temperatures and pressures and that will  cause more stress on the plastic and rubber parts in the system. So yes, BMW cooling systems are a bit more consumable than the average Honda or Toyota, but it's pretty predictable and the cost is not unreasonable, if you're willing to turn a wrench.

mr2s2000elise said:

Knurled. said:

Germany has yet to figure out how to make viable plastic or rubber.

Which shocks me, since I have been hearing about “german engineering”  since i was a kid 

 

Oh, the engineering is stellar.  The materials science is not always up to par.  It's actually because of the stellar engineering that we tolerate the substandard materials.

C&D did a long term road test of an E36 M3.  I recall that the car ate FIVE wheels during its 40k miles with them, because bumps are illegal in Germany so German wheels are typically cast out of a grade of aluminum slightly less soft than cold peanut butter.  They also noted that the dashboard sprouted a large crack.

A reader wrote in to complain about this, if any other car "sprouted a crack in the dashboard" while it was still less than a year old, they'd mercilessly take them to task.  "Ed." responded: "The dash could have sprouted daffodils and we wouldn't have cared."

In reply to Knurled. :

Wheel durability is definitely an issue on a lot of the German cars.  Audis are no better there.  Interestingly, within all of those brands, it seems like some of the wheels are extra fragile, yet others hold up fine.  I haven't damaged an M parallel yet (knock on wood) despite our roads looking like the surface of the moon.  Then again, they are forged rather than cast. 

I am considering using a BMW coolant pump on my street rod. wires on the pump #1  and #4 are 12 volt + and -  but #2 and #3 have me wondering  if  their function is some sort of pump speed regulation?  If the pumps just run on the full 12 volts  and are cycled on and off as needed, then I'd expect to be able to run the pump through a relay controlled by a temperature sensor and ignore connections 2 and 3. 

Extra information: I presently use a belt driven Toyota Corolla water pump to cool the engine, a 3.7 Liter Mercruiser inboard engine, in this street rod.  There is not a lot of room for a radiator so I use a Volvo crossflow radiator that fits when rotated 90 degrees to be a downflow radiator.

In reply to Knurled. :

Some German vehicles are said to contain outsourced parts.  Could the problem of deteriorating plastic come about from its manufacture outside of Germany?

Duder said:

"Apoplectically Complicated" - so the cooling systems themselves are filled with rage? 

Having owned an E36, I'm quite willing to believe that.

To be fair, the only thing about BMW plastic cooling systems that gave me more trouble than German or American cars with plastic in their cooling system is that while other plastic radiators typically start with a slow leak, BMW radiators completely blow the upper barb out of the radiator and drain their coolant immediately.

dennisg said:

In reply to Knurled. :

Some German vehicles are said to contain outsourced parts.  Could the problem of deteriorating plastic come about from its manufacture outside of Germany?

If you're outsourcing a product, it's on you to ensure your supplier can meet your standards. I think this is more of a problem with how to model plastic failure modes - the strength of plastic changes with time, heat cycles, and load cycles, and is a lot more complicated than metal.