Expansion Tank
 

Any DIY for the expansion tank? Is it an easy or difficult job? TIA, Sam

Super simple. 45min tops. Use a flat blade screwdriver to lift up the clip that locks the hoses on. The sensor at the bottom twists about 1/4 turn counterclockwise to remove. That's pretty much all you need to know.

You're supposed to change out the coolant every two years so and the hoses don't typically last that much longer than the tank so consider doing those too.

To completely flush the coolant you have to drain it from the block but there is a blue plastic screw on the bottom of the radiator on the drivers side that will drain roughly half of it.

Thanks wsmeyer for your reply!! Also how do I get rid of air in the system?? Do I have to change my cap to?? TIA, Sam

They recommend replacing the cap at the same time as the tank. You rarely hear people having caps go bad so up to you.

The expansion tank sits higher than the radiator in the E70 so it will purge the air out by itself. The instructions say to fill coolant to max, idle car for 2 minutes with cap off, refill to max if necessary. Check it again in a few days.

If you want to maintain your BMW yourself it's almost a necessity to get yourself a copy of the factory service software.

TIS = Technical Information System
WDS = Wiring Diagrams and Schematics

They are not complete step by step manuals as they are designed to be used by factory trained mechanics but if you know how to work on cars they'll have all the info you'll need.

Just do a search on ebay for "BMW E70 TIS" and you'll find them.

Few more thing to add:

- mix the coolant with distilled water (50/50 in most cases)
- after you replace the tank, make sure you air out the cooling system (turn the car on, do not start the engine, turn hvac on, set temp to the highest you ca, turn the fan to the lowest fan speed you can, leave on for 15 minutes, listen for pump running: front of the car driver side)

Keep in mind that is not true for the 4.8i. That was the case on my 4.4i and I believe it may be for the 3.0 but on the 4.8i there is no such bleed procedure. You just fill, leave cap off run at idle for a few minutes, refill if necessary and you're done. WSMEYER explains above as well.

Making mental note to self to remember to ask people what engine they have before giving too much advice

I want to thank everyone for replying to this thread. There should be a sticky DIY section on here like other forum have.

what!!!!?????

Sorry for misinformation. Hope you are not offended, I will double check. :D