my '01 330ci has a small leak where the expansion tank fits into the brace. Doesn't leak when system is hot, or several hours after. But in the morning i usually can see a wet spot directly under. I replaced the expansion tank about a year ago when I got the dreaded crack down the side. Is it just not fitting perfectly or is there a washer or o-ring in there somewhere that may be bad. Any suggestions would be appreciated
It sounds like you installed aftermarket cooling system parts. That’s strictly verboten! At that mileage and age the cooling system needs to be overhauled. This includes:
- water pump (Scaleri or Graf)
- thermostat (Whaler)
- upper and lower hoses (continental or dealer)
- radiator (Nissen or Behr)
- lower hose temperature sensor o-ring
- expansion tank (Modine)
- expansion tank cap
- expansion tank bracket (factory)
- block drain plug o-ring(dealer)
- BMW coolant
- distilled water (AND ONLY DISTILLED WATER)
Go to www.realoem.com and enter the last 7 characters of the car’s VIN. Hit enter and bookmark the page. I buy parts from fcpeuro.
It’s actually a German company that supplies/supplied parts to BMW. Two bits of advice:
1. Do not overfill the expansion tank. When cold the top of the red float should be just above the top of the tank’s rim. I know what the owner’s manual sez, but reputable techs have noted here and at E46Fanatics that overfilling the tank is the #1 cause of tank cracking.
2. Buy a 1.4 bar (~19psi) cap for the tank. This is the cap used on the E30 expansion tank. The M54 cap is 2.0 bar (~29psi). I used a 1.4 bar cap for years on my E46.
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