1st Gen "How To" How To: Replace Coolant Expansion Tank (Gen1)

How To: Replace Coolant Expansion Tank (Gen1)

by Ofioliti


My coolant expansion tank split along the seam so I replaced it. Here is the DIY "for dummies" with pics! Maybe it will help someone...

First, make sure the engine is cool. Let the car rest for an hour or so to be sure the coolant isn't hot.

Remove the coolant from the tank. I used a cheap "turkey baster" from a hardware store:




Remove the upper hose from the expansion tank. The oem hose clamp is loosened by squeezing the two tabs together with pliers. You can slip the clamp down the hose then pull the hose off:







Next, remove the nut holding the tank to the car:




Now, you need to lift the tank off of two holders underneath and remove the lower hose attached to the tank. The tank has two "nipples" just sitting in two holes of the holders (see picture further down when the tank is removed).

The ignition coil pack is kinda in the way to remove the tank and work on the hose, so I removed the coil pack. I first unhooked the battery. Maybe this wasn't necessary, but I didn't want to be screwing with the electrical components while the battery was attached. Since this is "for dummies" the battery is in the boot (for the Cooper S) :lol::




To remove the ignition coil, remove the four bolts on the top:







As you remove the ignition coil, be careful not to lose the four rubber gaskets underneath. They will probably be stuck to the base or to the engine:




If the gaskets look cracked and worn, they should be replaced. Mine looked OK after cleaning them up a bit.

Put the ignition coil to the side and out of the way:




With more work space, you can work on the lower clamp. Loosen it by compressing the tabs again, and work it down the hose. Twist the tank free of the hose:




This is what it looks like with the tank removed:




Attach the lower hose to the new tank and re-clamp it. Insert the tank into the two holes and reattach the upper nut. Reattach the upper hose:




Reattach the coil pack. Don't forget the four rubber gaskets at the base. Recommended torque for the four bolts is 9 foot-lbs:




Reattach the car battery.

Refill the coolant expansion tank with coolant (I used the MINI coolant from the dealer mixed 50:50 with distilled water).