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Thread: 540i Lower Temp Thermostat - Best Option?

  1. #26
    Join Date
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    BMW E39 540i M Sport
    Sorry to resurrect this thread, and, not wishing to restart any arguments here, but my e39 540i has the standard 105°C stat and it seems hot. I have a few options:-
    1. Leave as is and hope nothing pops. Seems like, on balance of available information, that 105° is too hot. My car is 16 years old, although its a super-clean and very well maintained low mileage car most opinion suggests some preventative action at an early stage would be wise. So...
    2. Waterless coolant. Preserves original operating temperature of the car but reduces pressure. this was may favourite option until i leaned about;
    3. Change thermostat. but to what temperature. 75, 80 or 88? I've been in touch with this chap
    http://abbes-performance.com/bmw-lan...mperature.html
    He is recommending 75° for my vanos engine, having much anecdotal evidence that this is the best option for this engine.
    4. Fit a standard 740d thermostat. like this
    https://www.sparepartstore24.co.uk/7...thermot-tronik
    Does this fit exactly without modification? any experiences, good or bad, with this approach?
    5. Do it with software - https://modbmw.com/thermostat-mod-m62/ I think the idea here is to tell the stat to open up by interfering with the map device...anyone here done this?

    cheers
    Fritzy
    Last edited by JimLev; 03-12-2018 at 02:39 PM. Reason: Fitzy, once is enough, your posts need to be approved, no need to post it 4 times.

  2. #27
    geargrinder's Avatar
    geargrinder is offline Having No Trouble Here BMW CCA Member
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    Something is broken about this thread.
    2003 M3CicM6 TiAg
    2002 540iT Sport Vortech S/C 6MT LSD TiAg
    2008 Audi A3 2.0T DSG (the daily beater)
    2014 BMW X1 xDrive28i (wifemobile)

    Former:

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    1995.5 Audi S6 Avant (utility/winter billetturbobattlewagen)


  3. #28
    JimLev's Avatar
    JimLev is offline Artifically Aspirated Moderator
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    Fitzy, once you have 10 posts they won't need to be approved. I deleted the 3 copies above.

  4. #29
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    98 540 6, SC'ed, 16psi
    Get the 88 Deg stat like everyone else with the TU motors. This will lower engine temps to low to mid 90's and lower the system pressure a bit too! You can go Evans too if you want. I love it in my car.

    Some get a code with the lower temp stats so do some searching on what to do if yours pops one.
    98 540i 6, 525 whp, 120 mph 1/4, V3 Si S/C'er @16 psi, W/A I/C, Water/Meth, Supersprint Headers, HJS Cats, 3" Custom Exhaust, UUC Twin Disc, Wavetrac LSD, GC Coil Overs, Monoball TA, AEM FP, Aeromotive FPR, AEM Failsafe AFR/Boost, Style 65's w/275's, M5 Steering Box, Eibach Sways, M3 Shifter, Evans Coolant, 85 Deg Stat, PWM Fan, 10" Subs, B.A. speakers, Grom Aux/BT, Still Rolling as my DD!

  5. #30
    geargrinder's Avatar
    geargrinder is offline Having No Trouble Here BMW CCA Member
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    As has been said a buncha times in this thread the 75 is WAY too cold and the guy selling that as a good idea clearly has CRS (craniorectal impaction syndrome). The 88 diesel Tstat is sweet tho ideally you get the matching software tweaks too to match and not throw codes. The software to open the MAP Tstat at all times is not a terrible solution but it’s kinda a workaround solution... though it’s a no wrenches no parts are instant fix if you can flash the ECU easily.
    2003 M3CicM6 TiAg
    2002 540iT Sport Vortech S/C 6MT LSD TiAg
    2008 Audi A3 2.0T DSG (the daily beater)
    2014 BMW X1 xDrive28i (wifemobile)

    Former:

    1985 MB Euro graymarket 300SL
    1995.5 Audi S6 Avant (utility/winter billetturbobattlewagen)


  6. #31
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    93 325is winter package
    Sorry to revive this thread but i have been searching for an answer which I haven’t found.

    Will the vemo 88c thermostat fit a non TU? It seems the thermostat uses the later model Clip style hose connectors.

    Has anyone used it on a Non VANOS set up?


    Sent from my iPhone using Tapatalk

    hope I made the right choice in chassis transition ... sigh, I miss my miata

  7. #32
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    Quote Originally Posted by supermanwithheat View Post
    Sorry to revive this thread but i have been searching for an answer which I haven’t found.

    Will the vemo 88c thermostat fit a non TU? It seems the thermostat uses the later model Clip style hose connectors.

    Has anyone used it on a Non VANOS set up?


    Sent from my iPhone using Tapatalk
    You have options https://www.bimmerforums.com/forum/s...is-the-pathway
    E85 fueled, Eaton m112 supercharged 4.5L M62TU, TTV racing flywheel, Spec stage 2+ clutch, 88c thermostat, eibach sway bars, wavetrac 3.15 lsd, m5 steering box, Quantum 340lph fuel pump, Dinan camber plates, some powerflex bushings, Supersprint headers, M5 cats, 2001 gas pedal upgrade and many other things done. all diy by me

  8. #33
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    Quote Originally Posted by 1999 540i m View Post
    Thank you for the reply. Saved me some money


    Sent from my iPhone using Tapatalk

    hope I made the right choice in chassis transition ... sigh, I miss my miata

  9. #34
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    2002 BMW 540iA
    I remove the TU 105C thermostat and here is my finding, there is a small o-ring on center cylinder that suppose to seal the thermostat when it is closed, but the o-ring seems to be swelled little, make it opening more difficult, I tried to boil the thermostat with the o-ring on and with the o-ring removed to confirm that. I also tried JimLev's trick by heating the spring with a torch, kind of messed up the spring a little, before it won't open when water is boiling but after it open a 1/8" gap (with the o-ring on). So even with the 105 C thermostat, if that o-ring is deteriorated, it can prevent thermostat to fully open.

    On the topic of 88C thermostat, I think you can swap the spring assembly and even the cylinder so you can still use the TU hosing with the MAP plug, I am wondering this 750i 90C thermostat 11531704704 https://www.turnermotorsport.com/e/p...hermostat-90c/ spring and cylinder can also been swapped with the TU thermostat, though the spring assembly and cylinder are different, but the holder clip and 2 holders are identical, what I am not sure is the diameter of the thermostat lid.

  10. #35
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    Why bother with a 90 degree thermostat when the 88 degree one (M67) drops right in?

  11. #36
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    Well, M67 88 degree thermostat is almost 3 times more expensive.

  12. #37
    geargrinder's Avatar
    geargrinder is offline Having No Trouble Here BMW CCA Member
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    I don't think you can remove the wax piston part without destroying it. The springs would probably swap but whether that's enough I don't know. IIRC I think somebody tried this BITD without great success.

    There are 2 or 3 'fudgey' ways to get the lower fixed t-stat in a TU motor, and back when it was hard to get the 740D part OK I could see those being worth trying, but, honestly... now that you can get the 'proper' part from ECS for a little over a hundred bucks, and have it plug and play perfect fit... I can't see going any other way...

    FWIW PN: 11532248542
    2003 M3CicM6 TiAg
    2002 540iT Sport Vortech S/C 6MT LSD TiAg
    2008 Audi A3 2.0T DSG (the daily beater)
    2014 BMW X1 xDrive28i (wifemobile)

    Former:

    1985 MB Euro graymarket 300SL
    1995.5 Audi S6 Avant (utility/winter billetturbobattlewagen)


  13. #38
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    FWIW I got a BEHR unit for $60 from Amazon.de. Turner is showing the 850 t-stat as being NLA.

  14. #39
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    2002 540i
    i have 2002 540i.. what thermostat would be best option.. or what to do about 'engine too cold' signals

  15. #40
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    Quote Originally Posted by theWalkinator View Post
    Well, M67 88 degree thermostat is almost 3 times more expensive.
    the 88c thermostat
    Last edited by ninetyseven1; 03-02-2019 at 11:14 PM.
    Electric Fan conversion, 840Ci thermostat, Dinan style CAI,de-screened MAF, Dinan transmission chip, 255lph LS1 fuel pump, drilled slotted rotors, 3.15 differential, Bel rx65 radar (hard-wired). Hemi Killer!

  16. #41
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    Hi dears,
    Sorry for posting on this old thread, I got this done in a different way with the stock electronic thermostat, I basically modified the map of the thermostat to open (based on my ME5.2 for my 1996 540i) at 95~ degrees. First it was not working then I discovered there are a few other things to change around (like thresholds for it to be under DME control, otherwise even if the target output temp of the map is lower than the actual coolant temp it wont open because it wasn't under DME control because of those thresholds, there are two of those, one based on intake temp (43~ c), and another based on car speed (180 km/h), both with particularly high values.

    I had the chance to modify few other things too, ignition advance for example (Just a slight touch, the background story with this car is that it had already a few non OEM maps loaded, and I roll-backed everything to stock when I bought it as I didn't like what was there), rpm limiter and speed limiter (the last two totally unnecessary for me as I the top speed I have driven the car is below the limiter (250 km/h), and the stock RPM limiter is set at 6100, I would not normally hit it, but as I was there I just modified it).

    With this the car oscillates between 100 and 91, which for me is quite on the spot, there may the 91 being just a little colder than what I would like but it is because of the hysteresis used to take a threshold as valid, I can touch it but I prefer to leave it like this.

    Along with this mod I did also changed the thermoswitch for a 91/99 one (61318363677), while I can work on the tuning a little more (for some slight gains in fuel economy with the ignition and the AFR maps as the stock maps run quite rich-mid on RPMs) everything works in harmony so far so I don't feel like touching anything else in the short time (Aside that I have to change the orings of the tube that goes from the pump to the back).

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