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Thread: Coolant thermostat

  1. #1
    Z8 Ate My Homework! Norcal's Avatar
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    Coolant thermostat

    So I had my 10 year coolant system maintenance done at Peter Pan a couple years ago. Soon after, perhaps a year or more ago, my car began running a bit warm... Just a tic past center. It never goes higher, even in 110 degree weather. I took it to PP last year... No verdict. A couple weeks ago on my way home from work, on the eve of our spring fling trip... Car throws a code!
    "Engine coolant not coming up to temp". Talked to Matt, and it sounds like just a Sensor. Seems that when they did the hoses, they reused the sensor. I'll take it in next week, and have the radiator done too. I think we should add the radiator to the 10 year coolant system service.

  2. #2
    Wait up, don't do the radiator just yet! Carlos is about to lay out a really important new radiator story, and solution!
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  3. #3
    Z8 Ate My Homework! Norcal's Avatar
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    Ok, but I think I'm in on the 9th so....
    I just figured it was a good time to do it? I'll wait for Carlos.

  4. #4
    You can order the new radiator directly from Dwight at Zionsville Autosport, but I think we're in the process of trying to arrange a group buy, as the radiators we have have about an 8-10 year life expectancy, so we're all due for new ones pretty much now. It's exactly the same as the e39 M5 unit.
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  5. #5
    Z8 Ate My Homework! Norcal's Avatar
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    Cheaper than through BMW I assume?

  6. #6
    About the same, but it's all aluminum, without those stupid cracking and snapping plastic 'necks'.
    Andrew Macpherson

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  7. #7
    Team Z8
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    Excellent news on the radiators...I'm looking now at places for the ten year service.

  8. #8
    I'd have no problem recommending Jack at Center BMW, he's the Z8 tech there, to book him call Paul Sanhaphakdi on (818) 231-9304 and say you're from the Z8 forum.
    Andrew Macpherson

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  9. #9
    DSC Off JohnAnthony's Avatar
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    Quote Originally Posted by Norcal View Post
    "Engine coolant not coming up to temp". Talked to Matt, and it sounds like just a Sensor.

    this is a common issue with the S62, the thermostats seem to have a very short lifespan (1 - 2 years depending on your luck and where you live), it's usually NOT the temp sensor on top of the thermostat housing that fails

    people who drive in cold weather (e.g. NYC winters) the car will not be able to maintain 79C coolant temp on the highway

    people who live in warm climates (e.g. FL, TX, etc) will probably never notice a failed thermostat because the ambient temp is warm enough that the coolant easily shoots past 79C
    [albeit slower than it would for your climate, but you will eventually throw a code when the thermostat start opening up at a temp far lower than the 79C it is meant to]

    for me driving the car year round I can easily spot a failed thermostat before the onboard computer even gives me a code for it and it serves as a simple reminder to do a coolant flush (every 2 years)




  10. #10
    How do we check the thermostat is functioning? Since all our cars are 12ish years old, and so far I haven't heard of any being changed, it seems we need a system to check these things?
    Andrew Macpherson

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  11. #11
    DSC Off JohnAnthony's Avatar
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    i use the OBC Test No. 7 which reads coolant temp digitally

    https://www.youtube.com/watch?v=cXrWrkEqClU

    to check if your thermostat is fine you observe the temperature rise from a cold start
    -if the thermostat is functioning properly the coolant temp will continuously rise from COLD to 79C (& based on ambient temps it will continue to rise past or HOLD at 79C)
    -if the thermostat is failing the coolant temp will begin to rise but when it reaches the mid-70C it will show a drop in temperature before rising

    now i don't know if you can unlock the OBC menu on the Z8 (it looks like you have the knobs you need)
    figure our witch knob is which since you have TOP & BOTTOM knobs instead of LEFT & RIGHT knobs:
    LEFT: should be the knob that you press and it displays your mileage *press the knob without the key in the ignition*
    RIGHT: the other knob

    NOTES:

    >how does the S62 thermostat work?

    the thermostat has an OPEN & CLOSED position which is temperature dependant
    the position of the thermostat will determine whether coolant is allowed to flow into the radiator to dissipate heat, or if it will simply continue to flow through the engine to collect more heat
    the thermostat will be in the CLOSED position when coolant temperatures are <79C
    the thermostat will be in the OPEN when coolant temperatures are >79C

    the thermostat has a cylinder filled with wax
    when this wax is heated by the coolant it expands and the cylinder pushes the thermostat OPEN
    when the wax is chilled by the coolant it shrinks and the cylinder allows the thermostat to CLOSE




    >who uses this style of thermostat?

    this thermostat design is also used by:
    E34 M5
    E39 M5
    Lamborghini Murcielago
    a bunch of International & Freightliner trucks
    & a couple of very old Peterbilts
    ...the E60 M5 has the exact same design, but different part number


    >what constitutes a failed thermostat?

    a failed thermostat is a thermostat that is not able to warm up and maintain a coolant temperature of 79C in winter conditions.
    So a failed thermostat is hard to spot for Z8 owners since they mostly use their cars in the summer


    >what are the effects of a failed thermostat & when will the car throw a code?

    -a failed thermostat as established will allow coolant to flow into the radiator at temperatures bellow 79C
    -this is not good because the ECU is adjusting fuel trim in order to make the engine warm up, but instead the thermostat keeps the engine in this warm-up mode longer
    -the engine oil is also affected as the coolant will not allow the oil to come up to temperature and you are essentially running on relatively luke-warm oil
    -when the thermostat is NOT changed out the severity of the failure increases, eventually the thermostat will allow coolant to flow at temperatures bellow 69C (maybe even 59C)
    -at this point even in summer months the thermostat opens so early that the engine remains very cold triggering the fault code Norcal reported



    words of advice
    -this is not a cheap fix if you go to your dealer (i've been quote $1600, and I only asked for $#!%@-n-giggles)
    -I'm currently on my 3rd thermostat (original, 2nd, and now 3rd) my 2nd thermostat was put in by an indy and it cost $600-odd bucks
    -I choose to do the work myself and i always suggest Z8 owners do the same, these are not complex machines (this model thermostat was being used in Peterbilt trucks from the 1960s, ref. RockAuto part number: 613080)
    -the part is only $150 from BMW, $50 from Behr, or $29 from STANT.... don't buy the Lamborghini one it's $250... but definitely buy the Lambo gasket as its cheaper than BMW gasket
    -if you do the job yourself it is time intensive the first time, but by your second thermostat you should be able to get it done in 30 minutes
    -also the thermostat housing will require some VERY hard yanks in order to free it


    P.S.

    there is another way to test it, but it is MUCH less accurate

    symptoms of a bad thermostat (as explained above) will have an affect even on the oil temperature.
    now I don't see an oil temperature gauge on the Z8 dash so you'll have to go off the coolant temperature gauge alone.

    looking at the coolant temperature gauge you should have:
    4 white marks/dashes
    1 blue mark
    1 red mark

    the 12 o'clock position is a temperature ~90C
    the first white dash (your cold side) i believe is about 50C
    the second white dash is about 70C

    when the thermostat has failed the needle will sit very close to the second dash
    when the thermostat is working fine in summer months the needle will sit at the 12 o'clock position
    when the thermostat is working fine in winter months the needle will sit between the 2nd dash & the 12 o'clock position

  12. #12
    Fantastic info, thanks so much!
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  13. #13
    Z8 Ate My Homework! Norcal's Avatar
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    Thank you for all the details. I'm not sure this is my type of failure. My gauge is running past 12:00 on hot days, and just less than 12:00 on cool days (normal for my car), leading me to assume that the temp reading is wrong, or that the thermostat is not opening soon enough. Either way, it's probably time for a new one.

  14. #14
    DSC Off JohnAnthony's Avatar
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    Norcal even if this is not the issue you are having the above test(s) can only be done with winter conditions + highway windchill.

    cool summer weather won't be enough because the ambient air temp has to be cold enough that it tries driving coolant temp below 79C.

  15. #15
    Guys, heed JohnAnthony's advise. I do my cooling system on my car every two years and I've changed the thermostat every other time just because I can and its cheap. Of course, I'm doing the work myself. I also posted a message about a month ago about the plastic radiator, and I'm not sure that, other than MacFly and NorCal (who's experienced first hand), anyone paid attention. The cooling system is the Achilles heel of most BMWs!!
    C.A. Cardenas (AKA Dan)2003 (last one?) Z8 - Hellrot / Sport Rot Original Owner - Munich Tourist Delivery-- Others --1988 M6 - 32K mi. - Original Owner1989 DINAN 750iL - 73K mi. - Original Owner1998 M3 - 63K mi. - Original Owner2015 X5 (F15) Diesel - Daily Driver2008 Porsche Turbo Cab - 9K mi. (Mezger motor/6-sp. manual)

  16. #16
    I know we're talking about getting a group buy of the radiators arranged, maybe we should look at the thermostat too?
    Andrew Macpherson

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  17. #17
    DSC Off JohnAnthony's Avatar
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    Quote Originally Posted by macfly View Post
    I know we're talking about getting a group buy of the radiators arranged, maybe we should look at the thermostat too?
    i don't know if anyone does group buys for thermostats...

    ...found this if you guys want BMW instead of Behr parts, but this kit is a little weird
    Search 11537835558 - ECS Tuning

    What it includes:
    BMW Thermostat [11537835558]
    BMW Gasket [11531312287]
    BMW Bolts [11141747632] x2 & [11141747633] x1
    BMW Coolant 1 gallon [82141467704]

    What it really should include & what you want to buy:
    BMW Thermostat [11537835558]
    BMW Gasket [11531312287]
    BMW Coolant 1 gallon [82141467704] x2BMW O-Rings 31x2.5mm [11531406249] x8 [if a first timer order x12]
    BMW O-Rings 18.3x3.6mm [11531407002] x4 [if a first timer order x6]
    Silicone grease [use on the o-rings]

    *yes, even if this isn't your first time doing this job you will likely cut up a couple of o-rings, plus they don't deteriorate if you keep them sealed and in a drawer
    *if you're a first timer just buy extras and hang on to any that you don't cut up
    *don't worry about getting silicone in the coolant, the amount that makes its way in will be negligible

  18. #18
    Team Z8 tomfakes's Avatar
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    Quote Originally Posted by ///M Blitz View Post
    other than MacFly and NorCal (who's experienced first hand), anyone paid attention
    I had my guy check this out as part of my pre-trip service. He said it's ok for now, and it did just go 1750 miles in a week.

    If we get an upgraded component available, I'll definitely be in for one of those, and get that fitted, probably before next summer

  19. #19
    The radiator we're working on is an all aluminum one, so it is for sure an upgrade.
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  20. #20
    Z8 Ate My Homework! Norcal's Avatar
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    Got my car back from my local independent. It was the thermostat. They also did both sensors. Just over $1,000.00... But I know they are not the cheapest around. Seems OK so far, on the ride home. Temp needle was running at 12:00. Where does yours run? Mine used to run at 11:00. I will order the all-aluminum radiator and have that done too at some point.

  21. #21
    DSC Off JohnAnthony's Avatar
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    Norcal the position of the needle is affected by ambient temperature & the coolant temp fluctuates up and down throughout a drive.
    If you guys had the digital read out you would see the coolant temp fluctuate +/-10 deg Celsius which is about the difference between the 11 & 12 oclock position.

    Also the needle is very sluggish, which I would assume is built into the instrument on almost any car since the amount of fluctuation in the readings would make owners think there was something wrong with the gauge.

  22. #22
    John, I'm going to swap out my radiator to a new all aluminum one, replace all my hoses and the thermostat in one big operation.

    There are several reasons to do all this, not least of which being that my entire front end was replaced incorrectly after some repairs a while back, and I've been meaning to get it properly aligned for ages. I'm using the opportunity to remove and replace all the other stuff, and I'm doing it with our team restoration and repair maestro, Carlos!

    Anyhow, do you have any other thoughts and or tips? (I already replaced all the sensors and MAF's at the dealership earlier this year.)
    Andrew Macpherson

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  23. #23
    DSC Off JohnAnthony's Avatar
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    i'm not familiar with z8 radiator issues, but sound like you're replacing most of the coolant system which is smart on a 10 year old car. as long as you take care of the thermostat, that is the weakest link.

  24. #24
    Administrator thegunguy's Avatar
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    I'm definitely interested to hear about this project. I replaced the hoses, expansion tank, etc. two years ago, but I know the radiator is a time bomb with its plastic fittings.
    thegunguy

  25. #25
    Team Z8
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    Quote Originally Posted by macfly View Post
    You can order the new radiator directly from Dwight at Zionsville Autosport, but I think we're in the process of trying to arrange a group buy, as the radiators we have have about an 8-10 year life expectancy, so we're all due for new ones pretty much now. It's exactly the same as the e39 M5 unit.
    .

    Got the code for a bad thermostat and I'm looking at preventative maintenance, about to place my order for this upgraded radiator from Zionsville. Did anyone on the forum install this aluminum radiator or was/is the stock BMW part still the best option?

  26. #26
    The aluminum one is a definite upgrade due to the all aluminum construction, and thus longevity over the plastic-aluminum stock unit, but I don't think there's any thermal advantage.
    Andrew Macpherson

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  27. #27
    DSC Off JohnAnthony's Avatar
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    another option for those interested is the RK Autowerks radiator. Double check that it still fits the Z8. Oil cooler is definitely NOT needed unless you run a supercharger or you're a track rat

    http://www.rkautowerks.com/index.php/product/e39rkrad/

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