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Thread: Want a cooler running factory thermostat? For no cost?

  1. #1
    Join Date
    Jan 2006
    Location
    Ft. Lauderdale, FL
    Posts
    5,083
    My Cars
    98 740il, 00 540i,04 ZHP

    Want a cooler running factory thermostat? For no cost?

    Ok, so I bought that thermostat from Logic7Amps. It is marketed as a modified factory thermostat that runs at 90*C. Well I got it and put it in and it ran around 99-104*C. Then the last 6 months or so (since that's when I looked), it has been running at 107*C. That's no different than a factory thermostat. So why did I pay this guy $50 to modify it?

    He has been less than helpful trying to get that worked out, so I said screw it, took the loss and want to tell the forum to avoid that option and go with this one:

    Ok so I got the idea from this thread, so credit goes there: https://www.bimmerforums.com/forum/s...1#post27666301

    And his results, to save you the reading, are here: https://www.bimmerforums.com/forum/s...7#post28794577

    So when I started getting a mystery coolant warning after driving for a while, I decided to drain the system, pull the thermostat and try my luck at this before refilling and bleeding.

    As you would imagine, a factory 105*C thermostat will not open in a pot of boiling water. The Logic7 guy said to test mine do that and it should open. Well it barely did, so whatever mod he did to it didn't last.

    So I grabbed my little mini butane torch and heated the spring in a couple areas as described in the post linked. This is a trial and error thing, with over-doing it meaning you need a new thermostat. And you want to avoid the center portion that contains the wax pellet.

    Anyway, I heated it in 2 spots until I saw it briefly get red. The spring deformed a bit, don't love that but it still is springy. Put in a pot of boiling water, using my Fluke infrared temp gun and a meat thermometer, it started opening at 91*C and was pretty open at around 98*C. I couldn't get the water any hotter than that.

    So in the car, it seems to warm up as normal, but starts slowing down in the 90*C range. It tops off at 99*C, but will go up to 101-102 for a brief time. Keep in mind my A/C is on full blast and the ambient temps here are 95-100*F. I'd say that is pretty good. Occasionally KTEMP will show 104*C, but it drops down as soon as the RPMs increase. A lot of times it is running in the 90-95 range depending upon engine conditions, ambient temp, etc. The nice thing is, the car can still control the thermostat with the DME so getting on the highway under hard acceleration, the temps drop down good.

    It's been like this a week now (didn't want to prematurely post). Just wanted to post this up for you all who want lower temps without having codes/CELs/expensive thermostats.
    Last edited by racer2086; 08-09-2018 at 09:10 AM.
    '98 740il | 9/97 build | schwarz 2 | sandbeige | 5AT | 270k
    '04 330i ZHP sedan | Mystic blue | Alcantara | 6MT | 120k
    '00 540i sport | Titanium silver | Black | 5AT | 152k
    '85 Mustang GT convertible | Medium charcoal metallic | Gray | 5MT | 216k | one owner, all original

    mods: m-pars | Bilsteins & B&G springs | ValentineOne | StealthOne
    retrofits: full nav | MKIV | bluetooth TCU | BM53 w/ AUX input | video module w/ AV input & backup cam | oem sirius xm | xenon | shades | PDC | rain sensor | BMW DWS TPMS | lighted door handles | front seat heaters | heated steering wheel | euro rear fog lights | ski pass | folding mirrors


  2. #2
    Join Date
    Oct 2013
    Location
    Louisa, VA
    Posts
    371
    My Cars
    2007 Z4 M Coupe
    Hmmm. I need to check my temps since I got the same modified tstat from that guy.
    Current: 2007 Z4 M Coupe (blue/black)
    Previous: 2001 740iL Sport (black/black), 2000 528i Sport (black/tan), 1995 318is (black/black), 1991 318is (white/black)

  3. #3
    Join Date
    Jan 2006
    Location
    Ft. Lauderdale, FL
    Posts
    5,083
    My Cars
    98 740il, 00 540i,04 ZHP
    Check it and see if it is still doing good. Very easy to heat it and relax the spring a little. Works great. So far.
    '98 740il | 9/97 build | schwarz 2 | sandbeige | 5AT | 270k
    '04 330i ZHP sedan | Mystic blue | Alcantara | 6MT | 120k
    '00 540i sport | Titanium silver | Black | 5AT | 152k
    '85 Mustang GT convertible | Medium charcoal metallic | Gray | 5MT | 216k | one owner, all original

    mods: m-pars | Bilsteins & B&G springs | ValentineOne | StealthOne
    retrofits: full nav | MKIV | bluetooth TCU | BM53 w/ AUX input | video module w/ AV input & backup cam | oem sirius xm | xenon | shades | PDC | rain sensor | BMW DWS TPMS | lighted door handles | front seat heaters | heated steering wheel | euro rear fog lights | ski pass | folding mirrors


  4. #4
    Join Date
    Oct 2013
    Location
    Louisa, VA
    Posts
    371
    My Cars
    2007 Z4 M Coupe
    Today was 90F outside and car held steady between 90-94, even in traffic. I'll try to remember to check it again, if we get around 100F.
    Current: 2007 Z4 M Coupe (blue/black)
    Previous: 2001 740iL Sport (black/black), 2000 528i Sport (black/tan), 1995 318is (black/black), 1991 318is (white/black)

  5. #5
    Join Date
    Oct 2010
    Location
    West Plains, MO
    Posts
    1,332
    My Cars
    '97 540i Dinan, 98 740iL

    Exclamation

    I bought the 88C thermostat (11 51 2 248 542) from Schmiedmann (Denmark) last year, and today since I had to drain coolant and replace a swollen top radiator hose, decided to install it. Unfortunately I hadn't done enough reading and found out, naturally after removing the existing 108C stat, that the 88C one only fits an M62TU. Which mine is not (prod. 06/97). The hose nipple is a bit smaller in diameter than the M62, which is not insurmountable, but one of the four bolt holes is deliberately in the wrong place.

    After doing some more reading today I have found that the one I should have purchased for my M62 is a 95C stat (11 53 1 745 476). Anyone want to buy a brand-new 88C stat for your later-model M62TU? Or swap if you also got the wrong one?
    '98 740iL E38 201k, TCG at 190k, 5HP24 at 195k
    '97 540i/6 E39 Dinan blower & stage 1 suspension 114k
    '93 525i E34 "Golf Ball" (hail damaged) 334k

  6. #6
    Join Date
    Aug 2017
    Location
    Wayne,PA
    Posts
    1,511
    My Cars
    740iL (E38 '01)
    Quote Originally Posted by racer2086 View Post
    Ok, so I bought that thermostat from Logic7Amps. It is marketed as a modified factory thermostat that runs at 90*C. Well I got it and put it in and it ran around 99-104*C. Then the last 6 months or so (since that's when I looked), it has been running at 107*C. That's no different than a factory thermostat. So why did I pay this guy $50 to modify it?

    He has been less than helpful trying to get that worked out, so I said screw it, took the loss and want to tell the forum to avoid that option and go with this one:

    Ok so I got the idea from this thread, so credit goes there: https://www.bimmerforums.com/forum/s...1#post27666301

    And his results, to save you the reading, are here: https://www.bimmerforums.com/forum/s...7#post28794577

    So when I started getting a mystery coolant warning after driving for a while, I decided to drain the system, pull the thermostat and try my luck at this before refilling and bleeding.

    As you would imagine, a factory 105*C thermostat will not open in a pot of boiling water. The Logic7 guy said to test mine do that and it should open. Well it barely did, so whatever mod he did to it didn't last.

    So I grabbed my little mini butane torch and heated the spring in a couple areas as described in the post linked. This is a trial and error thing, with over-doing it meaning you need a new thermostat. And you want to avoid the center portion that contains the wax pellet.

    Anyway, I heated it in 2 spots until I saw it briefly get red. The spring deformed a bit, don't love that but it still is springy. Put in a pot of boiling water, using my Fluke infrared temp gun and a meat thermometer, it started opening at 91*C and was pretty open at around 98*C. I couldn't get the water any hotter than that.

    So in the car, it seems to warm up as normal, but starts slowing down in the 90*C range. It tops off at 99*C, but will go up to 101-102 for a brief time. Keep in mind my A/C is on full blast and the ambient temps here are 95-100*F. I'd say that is pretty good. Occasionally KTEMP will show 104*C, but it drops down as soon as the RPMs increase. A lot of times it is running in the 90-95 range depending upon engine conditions, ambient temp, etc. The nice thing is, the car can still control the thermostat with the DME so getting on the highway under hard acceleration, the temps drop down good.

    It's been like this a week now (didn't want to prematurely post). Just wanted to post this up for you all who want lower temps without having codes/CELs/expensive thermostats.
    Just be a man and move to a cold place like we do!

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