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  1. #1

    Question Cooling System questions

    I think the thermostat on my E46 is starting to go bad as the coolant temp hovers around 85 degrees while running down the highway. I seem to recall that the thermostat shouldn't open until 88 or so. Does anyone happen to know for sure?

    While I'm in there, I plan on replacing the water pump, radiator, and upper & lower rad hoses. Is it necessary to replace the radiator or can I get away with doing just the expansion tank?

    Finally, can anyone convince me that I should upgrade to the EMP Stewart water pump? So far, I haven't had any cooling problems and as far as I can tell, the water pump on the E46 is a little more robust than on the E36.

    The car is 6 years old and has 102k miles and sees roughly 6~10 track days per year.

    Thanks,
    Anand

  2. #2
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    Quote Originally Posted by AG View Post
    I think the thermostat on my E46 is starting to go bad as the coolant temp hovers around 85 degrees while running down the highway. I seem to recall that the thermostat shouldn't open until 88 or so. Does anyone happen to know for sure?

    While I'm in there, I plan on replacing the water pump, radiator, and upper & lower rad hoses. Is it necessary to replace the radiator or can I get away with doing just the expansion tank?

    Finally, can anyone convince me that I should upgrade to the EMP Stewart water pump? So far, I haven't had any cooling problems and as far as I can tell, the water pump on the E46 is a little more robust than on the E36.

    The car is 6 years old and has 102k miles and sees roughly 6~10 track days per year.

    Thanks,
    Anand
    don't know if it is a common occurance, but the thermostat just broke in the open position on my wifes 2002 e46 325it. onlyabout 40k miles. under warrantee so they just replaced the thermostat.

  3. #3
    Senior Member SMOODY's Avatar
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    The thermostat is a weak point on these cars. I have already had to replace the thermostat on the 525iT and now the one on the 330i is starting to leak.

    I would definitely change the water pump at the same time. I did not do that on the 525iT and it failed on me out in the middle of nowhere. The charge for the tow ended up being more than the cost of the repair.

    I have a new thermostat and water pump for the 330i sitting in a box in the garage waiting for me to get a free Saturday or Sunday.

    I am not sure if the EMP Stewart pump is worth the cost or not. I have not had any cooling issues on either car, so I put the BMW OEM pump (plastic impeller) in the 525iT, but I got a one with a metal impeller for the 330i (It gets driven harder than the wagon).

    My cars only have 60K to 70K miles on them so I felt that I could hold off on the radiators, but if when they pass 100K I will probably look into replacing the radiator as a preventative measure.
    2001 330i (my car)
    2004 Audi Allroad (wife's car and family truckster)

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    I replaced everything except the expansion tank. 2 weeks later it broke. Change it all once you are at it. I didn't bother going for different pump or rad. You pretty much need to replace every now and then anyway I think. Those all alum. kits are way too expensive for me atleast.

    I wrote some stuff on my blog about the cooling system replacement on my E39 528i: http://skandsen.blogspot.com

    Also cn90 on Bimmerfest.com has a great writeup on changing the whole thing on an E39.

    I think the E46 should be similar to E39.

  5. #5
    Well, I ended up getting parts to replace everything. I'm going with an OEM Behr radiator and the rest of the parts, including the water pump, are OE from the dealer. Incidentally, the folks over at RRT were kind enough to advise me that the EMP Stewart water pump would be overkill, given my track schedule and lack of cooling issues.

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    For an e46, when replacing the radiator, expansion tank and the bracket that goes between them, is there any reason why you couldn't take everything out at once? Bentley lists seperate procedures for each, but I'm not sure why you couldn't pull it all at one shot, once you have the peripherals free. On installation, could you just do the reverse? I.e., assemble the radiator, bracket and expansion tank (and fittings) outside of the car, and slide everything in at once?

  7. #7
    Senior Member chicane's Avatar
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    Quote Originally Posted by Scany View Post
    I replaced everything except the expansion tank. 2 weeks later it broke. Change it all once you are at it. I didn't bother going for different pump or rad. You pretty much need to replace every now and then anyway I think. Those all alum. kits are way too expensive for me atleast.

    I wrote some stuff on my blog about the cooling system replacement on my E39 528i: http://skandsen.blogspot.com

    Also cn90 on Bimmerfest.com has a great writeup on changing the whole thing on an E39.

    I think the E46 should be similar to E39.
    Depends. The E46 M3's cooling system (radiator, water pump, stat) are all considered very reliable. The standard E46's less so.

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