You.


You got off without replacing the raditaor. Do yourself a favour and replace a bunch of stuff while you're at it. Big radiator hoses at minumum, and think when the last time the belt and tensioners was done, plus the water pump and its notoriously nasty plastic pulley.

+1
[emoji106]

Do every little coolant thing possible now and save the heartache.

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If after you check the fan clutch and replaced thermostat, radiator may be clogged if it hasn't been flushed it in long while. Use a good cleaner like Prestone Radiator Flush. Do the heavy duty cleaning procedure, not a 10 minute flush.

O.P.

How many miles? Looks like 150K...

- Search for the DIY I wrote a while back on cooling overhaul.
- Parts were also mentioned.
- Do not use the aftermarket tank, use only Volvo or CoolXPert brand (Check FCPEuro website).

Anyway, look for that DIY and do at least the partial cooling overhaul if < 140K. If > 150K, replace the radiator too.

Since the expansion tank is easy to change and a common failure, initially just change that out. It's not imperative to overhaul the whole system when one component fails. It is fine to just replace the cracked tank. Certainly check hoses to see if any are soft but I would fill it up and bleed the system and see if it runs normally before doing anything further. Once it is up and running you can easily check to see if fan is operating normally and if there are any leaks. Be sure to check the water pump for a seeping leak out the front. Hopefully it was not running hot very long and the cracked expansion tank caused the overheating rather than something else. I agree that it is important to use and OE or OEM replacement.

- If one is short of budget and drives only around town, then one can get away with changing only the failed component such as the reservoir.

- If one regularly drives out of town and long-distance, it is highly recommended to overhaul the cooling system after 120K miles (belts, pulleys, fan clutch, tank, rad hoses x2) because:
1. You can get stranded.
2. Towing cost from long-distance is expensive.
3. The M54 is prone to head gasket failure if allowed to overheat.

In fact, if you do a google search "BMW cooling overhaul", you will see hundreds of threads on this topic.

Not imperative was the key word but I should have been more clear. I agree long distance driving makes an overhaul more important and best practice is pre failure overhaul, part of preventative maintenance. However, that's not where we are in this case. The cost and time investment of an overhaul is significantly more than just replacing the tank and in this case, since the engine has already overheated, it can be a mistake to initially overhaul the system.

By replacing just the tank, whether daily driving is a long distance or not, you can find out if it is worth doing the rest of the cooling system or the engine is damaged beyond reasonable repair cost. The other components can be checked once it is running and one can also find a leak or other problem that could have caused the overheating. While best practice would be to do the rest of the components after that step, components like a water pump or clutch fan might last many thousand more miles. Of course, the higher the milage the more risk there is to go that route.

IMO, if you are a DIYer, best practice when owning vehicle that has over 100,000 miles and is as old as E53s, is to add up to 200 miles of free towing to insurance. If I am going to travel more than 200 mile I don't drive my E53.