Changing Engine Coolant

This is how i did it. I changed mine from the usual anti freeze to the OAT stuff. Take the 2 appropriate hoses off using the service manual guide. They are either side of the sills at the rear. Flush through using a hose as well as possible. Refit hoses. Refill system using plain water and Halfords radiator flush. Pressurise system using the Halfords esze bleed and the appropriate cap to fit the expansion bottle and a spare tyre. Make sure the spare tyre is not over inflated as you dont want to blow the hoses off. Open the bleed screw on the engine cooling rail till you only get fluid out. Open the bleed screw on the hose coming from the radiator. Its a knurled brass thumb screw IIRC on the passenger side. You can just about access this from the front services compartment on a S1. Open it till you just get fluid out. Remove esze bleed. Leaving the cap off the expansion bottle, start the car and let it idle till the temp reaches 65 ish. Hold the revs at 2000 rpm till you see the thermostat open at approx 85, it should then drop to about 80. Let this happen twice. You should then rebleed just the front radiator bleed using a rag to make sure you do not burn your fingers. Turn the car off and let it cool. You should then repeat this procedure but fill up with OAT anti freeze instead. You may have to repeat the bleed procedure a couple of times if you have variable temperature readings. I was quite suprised how much anti freeze was left in the system when i drained the radiator flush. If you are changing to OAT, you need to do a thorough flush as the OAT does not mix with OE antifreeze. The 2 if mixed will form a sludge apparently.

Dont forget to pump the spare tyre up.