Help with changing expansion tank

[X5E53John]

So im having to change my expansion tank as it has decided to split
While im at it ive decided to change the belts and pulleys and replace my ofh gasket
Ive read online about replacing the radiator hoses really not sure how far i should go in to replacing everything
Any help and advice on what to change etc would be a great help
Thanks john


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[andrewwynn]

Try to get OEM part. The dorman will get the job done but tolerances off enough to make it very hard to install. (done it twice).

The replacement should come with the transmission cooler thermostat. The old one will break during removal, I've always had to drive a screw into the old one to pull it out.

I didn't replace the hoses.

[bcredliner]

How many miles on the other parts you are thinking about replacing?

[andrewwynn]

Or in the case of rubber and plastic parts years might be more important


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[Overboost]

Genuine BMW or Modine expansion tank will be the best choice for reliability on the M54. As Andrew points out, make sure to get the automatic transmission thermostat as it will break when removing the tank.

[X5E53John]

Thanks for the replies
The car has done about 136k miles now Ive had it for about 2 years now
Im not sure on how old the rest of the parts in the system are
Its a 2002 e53
But was pretty well looked after by the previous owner
Where is the automatic transmission thermostat ?


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[X5E53John]

So I’ve managed to remove the expansion tank but on removal a spring with a plastic tip flew out of the larger pipe on the bottom of the expansion tank / radiator is this part the thermostat you was talking about as it looks like I’m defiantly going to have to replace this part as well


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[Clavurion]

That's the thermostat. Nr.4

[X5E53John]

Originally Posted by Clavurion

That's the thermostat. Nr.4

Thanks for the clarification ive had to dig the bottom half of the thermostat out of the rad after seeing a picture and realising only half had come out


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[andrewwynn]

Originally Posted by andrewwynn

The replacement should come with the transmission cooler thermostat. The old one will break during removal, I've always had to drive a screw into the old one to pull it out.

As described above. I forgot about the spring shooting out when it breaks in half.

Also for clarity that's not the radiator it's in; it's the transmission cooler/heat exchanger.

Where the radiator is an air/water heat exchanger this is attached to the radiator and does a water/oil heat exchange to cool the transmission oil.

Apparently has a thermostat so it allows the transmission to get up to an appropriate working temperature