Cooling system

[Jimmyjohn]

Just bought a 1999 323i vert and heard the plastic cooling is trash and will overheat and crack, was wondering what do other people use. I heard metal ones were good if anyone has any links to it

[shogun]

On my E36 M3 I have all original cooling system and did not have any problem, no need for metal radiator. A car radiator's average lifespan is 60,000–80,000 miles, but it can last up to 100,000 miles or more if well maintained. All these parts have a hard job and need to be replaced in certain intervals, not only the radiator, also the water pump, hoses, thermostat, expansion tank etc.
Here more threads with same subject radiator lifespan https://www.bimmerforums.com/forum/showthread.php?1388858-radiator-lifespan
Survey-How-long-did-your-stock-radiator-survive https://www.bimmerforums.com/forum/showthread.php?1673279-Survey-How-long-did-your-stock-radiator-survive

[R Shaffner]

The underlying cause for fragile cooling systems on these cars has been hotly debated here.

Some blame the plastic parts, and non-BMW replacement parts. Others blame the hotter-than-normal temps that these cars often endure because of the high temp MAP termostats. (I don't know about your car, specifically, but many of the stock thermostats from this period were rated at 105C.) And other owners here blame the higher-than-normal pressure caps. (Many from this period are 2.0 Bar, which is somewhere around 29 psi -- MUCH higher than normal, and way too high in my opinion.)

Actually, I think all of the above are partly to blame. So there are things you can do to make life easier and the cooling system parts last longer.

First -- Never overfill the system! (Never above the full mark when cold.) A little low is fine. But not so low that the expansion tank empties.

Second -- Understand that most of these systems must have the air bled out of the bleed screw, when being refilled from too low or empty.

Third -- If you have a 2.0 bar cap you can get the 1.4 bar cap that works fine, and will release pressure at a level that is closer to normal. (Contrary to some opinions, a lower pressure cap never causes a sudden boil-over, and it can help prevent a repture that can leave you stranded.)

Fourth -- If your car has a high temp thermostat (over 100C) you can prob get a cooler one that will reduce both the heat and pressure these old plastic parts have to tolerate.

And Fifth -- Preventative maintenance can really help. Best to replace plastic parts before they fail -- when replacing one, go ahead and do others that might be old and fragile.

And finally, this thread might help (if your expansion tank is beside the radiator, instead of above it):

https://www.bimmerforums.com/forum/showthread.php?2392287-BMW-Expansion-Tanks-Caps-and-Bleeding-Explained

[gc325is]

I have never heard of the higher pressure cap limit. A loss of coolant will ruin your engine in a short period. If you do regular maintenance with hose, radiator and water pump changes you may never see a problem. If you just replace after a leaks occur your still into a water pump or Radiator every ~6 years even fan blades will break with age. The sum is after 30 years I have replaced 4 pumps 4 radiators 2 fan blades. I have the original cap but on the 2nd reservoir tank and hoses. The interior heat exchanger is a common leak too. All of the radiators were broken at the top hose connection except the one when the fan blade went though it when the water pump failed.

[Eric93se]

To add, there is a factory flaw that prevents the fan temp switch from coming on at the set temp, this flaw is present regardless of the unit. The fan will come on ~15C higher than the set point and can be fixed by simply wrapping the body of the sensor with an insulator (Styrofoam and duct tape in my case) and it will allow the fan to come on exactly at the set temp.

Very important to get all the air out when filling an empty system, you want to fill with the bleed screw completely removed and fill the reservoir to the brim, close the bleed screw when coolant comes out and then remove the excess from the reservoir with a turkey baystor ($2 supermarket).

The reservoir needs to be a quality brand, Behr, Mahle, Beck Arnley, or it will fail early.

Read the FDM thread (fan delete mod).