Cooling system expansion tank - anyone's blown up?

N

Newyorkmikey

Member
One of my recommendations after the service was that the cooling system expansion tank is stained, and should be replaced. The mechanic showed me a blown one, split right down the side, and said it wasn't uncommon.

Just wondering if anyone has had this happen? I'm not sure whether to treat it as urgent, or just get it done next time.
 
Never heard of it as a common problem on cars. Sounds like an urban myth and money making idea.

Staining is only a result of dirty coolant expanding and contracting back and forth to the tank.

Was this BMW or a local indy/mechanic?
 
It happens on E36 BMWs, but only now that they're over 10 years old and the plastic is becoming brittle and it generally is a result of the water pump failing and overheating of the engine. Without going down the road to look at my Z I cannot remember if it is a similar design - stuck on to the side of the rad.
Seems like an odd precautionary mesaure on a car that must be less than 6 years old.
 
Surely it wont blow up though unless its overfilled or air is getting into the water system. The water level will just rise and fall with pressure build up.
 
I puruse the E46 forum a lot. This is a common problem on E46's with the M-54 engine.

The plastic looses its elasticity over time...

Since there is a lot of engine parts that are common from the E46 to the Z4, the same issues will cross over also.
 
I can see if after say more than a decade that the plastic could go brittle and fracture but not on a <6 year old Zed?
 
cj10jeeper said:
Never heard of it as a common problem on cars. Sounds like an urban myth and money making idea.

Staining is only a result of dirty coolant expanding and contracting back and forth to the tank.

Was this BMW or a local indy/mechanic?
Click to expand...

This was a local indy, a BMW specialist (Peter Mabey BMW for any Sydney residents). Cost to replace would be $625 AUD (plus another $275 to replace the thermometer even though it was working fine!) hence my reluctance to do it if not a big risk (famous last words..!!!).

I guess 'blown up' isn't the best description. On the one he showed me the plastic was split from top to bottom, and that's normally associated with a loud 'bang' apparently, and the water emptying out of the system double quick time of course. So I would expect it's a brittle plastic sort of cause.
 
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