the reason you shouldnt be using dexcool or any standard 'organic acid tech' coolant is because your engine and heads are made out of alusil (aluminum is injected with silicon during manufacturing process), not normal aluminium, the afc or g48 that the bmw engine comes with has silicates added, with out this it will slowly cause the metal to pit, causing you problems. as to the tstat, when your tank bursts it does so because of excess pressure in your system, along with years of wear causing it to weaken. the pressure can be incresed due to your tstat not opening when it should, not nessacarly just when it gets hot, but under times of high engine load, your tstat has a heating element that will force it open even when closed, if this is not working as designed, when you hit 3000 rpm on a cold engine you have too much pressure in your system and the only place for it to go is out.

 

Hey Man,you need to check your facts. Alusil is a coating applied to the cylinder bores of the engine block. and under most circumstances there should be no coolant entering this area. Bmw used to use nikasil as a cylinder coating, this reacted with lower quality gasoline, causing pitting and corrosion to the cylinder boresresulting in excelerated wear and low compression. Silicates and organic acids are the same thing, they inhibit rust and corrosion in the cooling system, the later being beter as it lasts longer and protects longer. And the only way the tstat could cause excessive pressure would be in an overheat condition. I.E failure!! also why wouldnt the pressure cap expell excess pressure if there was a problem?

 

no, nikelsil is still the cylinder liner, finished off by only a polish, not boring. the crankcase is made of alusil, which is why if you run your finger across this block its smooth to the touch, a very good finish, even before its bead rolled. silacites and organic acids are not the same thing, they just serve the same purpose, this is why dexcool is classified as a OAT coolant and G48 isa HOAT, hybrid being the added letter. dexcool is solely organic, G48/AFC contains both organic and inorganic to protect agains corrosion, different types of metal need different types of protection. as to the tstat heater, yes obviously i cannot condemn anything on anyones car without putting my hands on it, however it is in my experiance that generally when the exp tank goes, the heater element in the tstat is not doing its job, also, this will only very rarely throw any fault, thanks to a ecu tune update, B177, that was to be done to all cars back in 04, and if by chance a fault does throw, its to be a non-mil event. but its not my car, so take your chance and save 30 bucks on the dexcool, but just so you know, a new radiator is about 700 now