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Thermostat Assembly

Discussion in 'E90/E92/E93 M3 (2008-2013)' started by carlgadams, May 6, 2015.

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    2008 E90 M3, 55,000 miles, check engine light is on and increased emissions is shown. I checked the gas cap and the performance of the car is fine. I took car into a respected independent BMW shop and they put the car on the computer and they tell me the thermostat is sticking open and the car is over cooling itself and the thermostat assembly needs to be replaced. Due to where the thermostat is located it will take most of a day to replace the assembly. As you might imagine, this results in a large labor charge (the parts are really not that expensive). Does this sound reasonable?
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    That depends on the fault code you have. There is a bulletin for the coolant temp sensor 12 07 12 which can cause running issues and a SES light. But if you have the fault for thermostat jammed open yes it will have to be replaced and they are not the easiest to replace.
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    Is there anything that should be replaced at the same time? One of those while you have it apart you might as well...
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    Hello Ken.S.330,
    I have a 2008 E92 also with 108,450 miles. Question: Do you have a leased car you plan on turning back in or do you plan on keeping the car? If you're deciding to keep it for awhile, then read on. Besides the thermostat change out on your car with 55,000 miles, have both the a/c & alternator/water pump/power steering belts inspected. I would highly recommend changing out the water pump and seal. Its a consumable like the tires/brakes are. Why not, everything is right in front of you or your mechanic. Not sure if you know this or not but the OEM BMW water pump uses a composite impeller pressed onto a metal bushing which is then pressed onto a stainless steel shaft which is driven by a plastic pulley which is driven by the serpentine belt. ECS Tuning sells brand new water pumps: the OEM composite impeller and a metal impeller water pump made by Geba for $260. Turner Motorsport sells a metal impeller water pump by BMW Motorsport used on the racing M Z4's for $600 + shipping. I would change out the OEM thermoplastic water pump drive pulley for an aluminum one. ECS sells one for the 540 which may match the thermoplastic one on the M3 S65 V8 engine but I am not absolutely sure. Turner told me that they raced they're E92 M3's using the thermoplastic water pump pulleys and had zero issues but I don't trust anything thermoplastic as an engine component. Have the drain plug opened on the radiator and have the entire cooling system flushed out. Get a high quality antifreeze and mix it with distilled water for 50/50 mix......I'd also add a good heat exchange fluid like Red Line into that mix. Bleed the air from the system and you're good for 100,000+ miles!
    I hope this helps you!
    Best Regards,
    John Coates
    BMW CCA #106598
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    Thanks John. I appreciate the info.

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