03 325i overheating problems

[chinoe46]

Well I bought an e 46 with expansion tank busted before I go ahead and replace should I be worried of any major problems the car might have I'm new to bmw but am totally excited that I currently have 2 but also the other has abs dcs going into limp mode appreciate the knowledge thanks

[MarcoZandrini]

The cooling system is the Achilles heel of the E46. It’s made of plastic, good quality German plastic, but plastic nonetheless. Plastic ages from the passage of time and the repeated heating/cooling cycles.

Let say thus once: the installation of aftermarket cooling system parts is strictly verboten. “Verboten” is German for “forbidden.” Why? These engines, the M54B25 engine in your case, are made of aluminum. They do not tolerate overheating at all. If you overheat the engine be prepared to either have a used engine installed or buy another car. An overheated M54 engine can be repaired but it’s costly.

Did the car come with any maintenance records? I bet not.

First things first: go to www.realoem.com and enter the last 7 characters of the car’s vehicle identification number. Hit enter and bookmark the page. This will give you the part number for every part in your car. Since BMW is German, the parts breakdown is very logical.

So what do I recommend? A full cooling system overhaul. Why? The consensus here and on other E46 forums (try E46Fanatics) is that the cooling system needs to be replaced at 100k miles. What does that entail. The following:
- water pump (Saleri)
- thermostat (Whaler)
- upper and lower hoses (Conti, a subsidiary of Continental)
- expansion tank (Modine and only Modine)
- expansion tank cap (Modine)
- expansion tank bracket (OE)
- radiator (Nissens (OE) or Behr (OEM)
- coolant temperature sensor in the lower hose (OE)
- engine block drain crush washer (OE)
- coolant (BMW and only BMW)
- distilled water
Some “while I’m in there” stuff:
- serpentine belt (Conti)
- idler and tensioner pulleys (INA)
- tensioner pulley torx bolt (OE)

Where to buy? I recommend FCPEuro. Why? Great prices, excellent customer tech support, fast shipping and a LIFETIME WARRANTY ON EVERYTHING IT SELLS! Some folks send their used motor oil to FCPEuro, the company sends them fresh oil back for free (plus the cost of shipping). Now, when you enter a part number you’ll get either 3 or 4 results on the FCPEuro website:
- a BMW branded part (expensive)
- a part made by the supplier of the part to BMW (aka “original equipment (OE))
- a part made by a supplier to BMW but not the supplier of this part (aka “original equipment manufacturer (OEM))
- aftermarket.

As noted above, aftermarket cooling system parts are verboten. So buy either OE or OEM parts. Buy a Bentley manual for the car. Do not buy a Haynes manual It doesn’t go into enough detail.

[jclausen]

Before dumping a ton of money into the unkown I would replace the expansion tank fill it with water and see what happens

[chinoe46]

Thanks

[fumigator]

+1 for jclausen

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[nonturbodan]

+1 to that as well.

Since it has probably overheated already I would do the bare minimum to get the car running and then I would try to determine if the engine was damaged. Replace the cracked expansion tank, cap and thermostat. See how it does with that. If it doesn't overheat and it doesn't overpressurize the cooling system, you can go back in and finish the job and do the radiator, water pump and all the rest once you know the engine is good.