Thread: Coolant flush
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      12-01-2012, 08:36 AM   #3
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Drives: E90 & Z4 Coupe
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Originally Posted by kiwi29 View Post
Replace the thermostat. Even if it might not have failed, you'll never know if it does or not because there's no CEL or error code produced from it. Check all hoses for dryness, cracking, rips etc. And keep an eye on the water pump if you haven't changed it yet
This is backwards. The T-stat will throw a code and will illuminate the SES light, so you will know when it goes bad. But "going bad" only means the heating element has failed in it, the t-stat will still operate properly. The only way to "keep an eye" on the waterpump is to scan the ECU for shadow codes that indicate a slow waterpump speed, which do not illuminate the SES. Once you find the code for a slow waterpump it means the pump is on the way out.