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E63 / E64 6 Series (2004 - 2010)
The E63/E64 BMW 6 Series builds on BMW's sporty heritage with aggressive lines and an incredible motor to back the design up. Available in coupe and convertible trims with a standard 4.8 liter engine producing 360 horsepower and 360 lb-ft of torque, the 6-series is a popular choice that exceeds expectations.

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Old 04-29-2018, 04:33 PM
03bmw745li 03bmw745li is offline
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Mein Auto: 2003 745li
coolant and trans fluid leak?

ok so hey guys, and gals of course! I kinda got a problem. got a 05 645ci e64 and I recently replaced motor and transmission. went entirely through motor to fix all seals and any known issues like valve seals etc. but here is my problem. IM leaking transmission fluid and coolant. coolant is leaking from hole in the bottom of the overflow canister which I assume it is supposed to if it builds up too much pressure or whatever. I also have a transmission fluid leak which looks to be coming from either the bell housing or from above some towards front of tranny(no fluid on torque converter though from what I can see). ODD thing is they both started leaking about same time. here is what I have replaced thus far since leak started. new water pump, thermostat, coolant overflow recovery tank and made my own coolant transfer pipe stint since it started leaking shortly after parts were replaced (cost me less than $15 if your interested let me know I can share how I did it, works well thus far). only thing I know is bad in coolant system is the secondary electric (auxillary) water pump for keeping warm air running while car is not running. cant imagine that would be a problem though. seems like my system is working as both large coolant pipes coming in/out of water pump get warm so that tells me its circulating. now I am not sure this is relevant, but my tranny does hard slam downshift when I stomp the pedal but is smooth otherwise. I don't get it. could the transmission coolant valve be causing this with flow blockage and/or is there anything that could relate the two?
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Old 04-30-2018, 10:14 AM
Rick D Rick D is offline
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Originally Posted by 03bmw745li View Post
thanks for reply however as stated, the coolant recovery tank was just replaced only to do the same thing the oem original did. as far as trans fluid its def trans fluid
Then my guess is someone poked a hole in it at some time or it was a faulty tank..

If the tank is leaking from a split or hole ( as you stated) then you need to replace the tank again....
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Old 04-30-2018, 05:52 PM
HerbP HerbP is offline
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If the expansion tank gets hot, it cracks very easily. Take it out & inspect it, or use a pressure tester on the system.
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