Expansion Tank Busted
 

Ive searched the threads and I havent found any complaints of a coolant tank cracking. My 4.8is expansion tank just cracked and all the antifreeze came out. Anyone ever had this problem? Is it worth getting a oem or a aftermarket. Should I replace all the hoses while im at it?

OEM replacement is the way to go.

Expansion tanks failing is a very, very common thing for most BMW's.

Your mileage will indicate what you should do as far as hoses are concerned. However, from personal experience and everything I read, once you start replacing components on your cooling system it stresses the old components you don't change and they start breaking as well. Probably best to replace the entire cooling system if you have anywhere near about 90k miles or so. I would use OE parts, but that is up to you.

Can someone please explain to me how replacing a cracked expansion tank will "Stress" the other components to failure? I am really interested because mine is leaking and I don't see how replacing this will cause my other components to fail.
Maybe a new water pump will affect old hoses and such, but a new expansion tank won't have any effect on your other components.. Unless I'm wrong

I am not sure if "stress" was the best word I could have chosen in the above post, but for one reason or another it always seems that at higher mileage, when you start to have components of the cooling system fail, many others are quick to follow.

Not in all cases. I replaced the waterpump, exp tank and upper hose ass'y at 105k miles. System is fine at over 150k miles.

I replaced my tank this Friday. I also replaced 5 of the 6 cooling hoses and new fluid. So far so good.

I too can't see it stressing the other components. People get failures of other items because it is time for them to fail. When you replace the tank, which was losing pressure, and leaking, you basically close the weak point in the system. What happens then, is the hoses and other stuff have to start working again at full pressure.

I think the component failure is when those people neglect the leaking tanks, and replace them when they leak like the Hoover Dam. Like all the fluid emptied out. The hoses are old, and now they are relaxed, because of the low pressure, rubber does have memory. Then all of a sudden, new tank, the cooling system is at full pressure, and this shocks the other components.

Replace your dripping tank right away, and I think you should be fine. Replace the expansion tank fill cap as well. Only reason I replaced the hoses, is because I am insane, and do preventative maintenance way ahead of time.

Correct. Never said in all cases. However, if you have any of the original cooling system parts at 150,000 miles, you are running on borrowed time. I feel your particular case should be taken as the exception and not the norm.

I agree it's the exception. Gone this far and I am going to ride it out to the failure, let AAA membership pick up the tow $s.

Currently in Dallas/Ft Worth TX area, 110 deg heat and done two tows of 6k lbs, sitting in stop and go construction traffic I have see the outside temp reading up to 122 deg. Suprised it's not failed something thus far!

lol. Yours must have been made out of unobtainium and not the plastic the rest of us got.