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Thread: Thermostat failure 3 times in a year

  1. #1
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    Thermostat failure 3 times in a year

    Hi all,

    I have VW Bora 1.6 BFQ engine with automatic transmission(model year 2005). 208.000 km.

    About 1 years ago, coolant was leaking from thermostat house. So, I changed thermostat house with thermostat and temperature sensor. I bought it as OEM part from VW.

    Then thermostat was failed 3 times until now.

    In the OEM part, “Mahle Behr” was written beside VW Audi logos.

    It failed in 3 months. Then, I changed only thermostat with aftermarket Mahle Behr part. It failed after 7 months. Again I changed it with mahle behr one more time. It's been 3 months. Then it failed agin.

    3 failed thermostats in one year...


    The coolant is G13 antifreeze %50 mixed with water.

    In the morning, I check the all temprature sensors' value. All shows the same. (engine temperature, radiator temprature and outside temprature)


    How did I understand thermostat was failed?


    I’m following the blocks in group 130 and 131 in engine group in the VCDS.

    Check reference: http://www.ross-tech.com/vag-com/m_blocks/130-137.html

    Group 130 Map cooling

    Block 1: Engine outlet Temperature [°C] --> The real engine temperature
    Block 2: Radiator outlet Temperature [°C]
    Block 3: Thermostat Duty Cycle [%]
    Block 4: Test ON/ Test OFF/


    Group 131 Map cooling
    Block 1: Temperature Engine outlet [°C] --> The real engine temperature
    Block 2: Temperature Engine outlet (specified) [°C] --> ECU tries to keep engine at that temperature. According to engine load, it changes. if load is low or normal, it keeps at 109.5 C or 105 degree. If load is high, then tries to keep at 94.5 or 90 C degree.

    Block 3: Radiator outlet Temperature [°C]
    Block 4: Thermostat Duty Cycle [%] --> how much thermostat is open. If engine temperature is bigger then specified engine temperature, it opens according to difference.

    (I wrote what I undestand from Blocks values. Please correct me if I misinterpreted something.)

    -In the first failure, temperature gauge went up in the high way from 90 Celcius degree to 130C. Also, engine was 125 C.
    -In the second failure, temperature gauge goes up from 90C to 95C, after awhile down again to 90. I was following from Vagcom, Engine Controller tries to keep the engine at 109.5 C degree. But, the temperature gradually was going up from 109 to 118 C degree although thermostat looked open(duty cycle more than %70, radiator temprature about 50C. the weather was very hot, about 40C ). Then, duty cycle %100 and fans start to run and temperature goes down to 105C. Thermostat is map-controlled thermostat.

    -And now, the third failure, gauge is constant at 90C. When I check on the VAGCOM, ECU tries to keep engine at (Group 131,Block 2 value) 94.5 C degree. but, engine temperature is moving between 94,5 and 99 C degree. The season is winter, radiator temperature is between 10 and 20 C degree.

    Another problem is that fuel mixture is going lean when temperature is goes up. If the engine temprature is bigger then the specified value for awhile, ecu makes the mixture lean. In VCDS Group 33 Block 1, lambda value is more than 10% , generally 15% or 17%.

    What is the problem? Please help me how to detect or solve this problem. Is it thermostat or Cooling temprature Sensor or something else?


    Thanks for your kindly help.

    Burak

  2. #2
    NostraJackAss Jack@European_Parts's Avatar
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    JPPSG and an auto-scan please.

    Is car modified?

    What is the use of the vehicle, ambient temps for region & use on a routine for cold start, range of normal operation and load requests subjected too?

    Is car with dual water pumps one mechanical and one electric?

    VIN number?

    What is condition of radiator, heater core and fan operation?
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    Above Magic! No Written record, AUTO-SCAN or Appointment = NO HELP!
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  3. #3
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    Quote Originally Posted by Jack@European_Parts View Post
    JPPSG and an auto-scan please.

    Is car modified?

    What is the use of the vehicle, ambient temps for region & use on a routine for cold start, range of normal operation and load requests subjected too?

    Is car with dual water pumps one mechanical and one electric?

    VIN number?

    What is condition of radiator, heater core and fan operation?
    Jack is right, would like a scan.

    Now, who did the install, and was it evaked down? Air in systems causes all kinds of random issues coming and going.

    JMO.

    LARIMORE

  4. #4
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    Hi all,
    the car is not modified. It is original. It is 1,6 BFQ 102hp engine with automatic transmission.
    I used it for daily driving.
    The car has one mechanical water pump.
    I changed the radiator 5 years ago with OEM part. I always use G12 antifreeze.

    Today I changed the coolant temperature sensor used LIQUI MOLY radiator cleaner, cleaned the coolant system with water 4 times and filled new G12+ antifreeze mixture and be sured there is no air in the system.

    After driving urban for a while, I checked the group 131 in the highway.

    When I open the heater %100, specified coolant temperature(block 2) is 94,5 C. At that time, real coolant temperature(block 1) is between 95 and 102 degree. Thermostat duty cycle(block 4) is generally between %60 and %80. Radiator outlet(block 3) is 30-35 Celsius degree.
    When I open the heater %50, specified coolant temperature is 99 C. At that time, real coolant temperature is between 99 and 106 degree. Thermostat duty cycle is generally between %40 and %60. Radiator outlet is 30-35 Celsius degree.
    When I close the heater, specified coolant temperature is 109,5 C. At that time, real coolant temperature is between 110 and 114 degree. Thermostat duty cycle is generally between %15 and %30. Radiator outlet is 30-35 Celsius degree.

    Are this values are normal? Outside temperature was 13 Celsius degree. The engine rpm was generally between 3000 and 4000 rpm. (speed is 100km/h and 130km/h)

    The real coolant temperature is generally 5 C degree higher then the specified value. I remember that the difference was generally 1 or 2 degree before. But, I'm not sure.

    however, what is the healthy or acceptable difference between The real coolant temperature (block 1) and specified coolant temperature(block 2) ? Have you ever check this values in your car?

    thanks for your replies.

    This is the coolant system of my car.
    Last edited by buzel; 03-10-2019 at 01:18 AM.

  5. #5
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    [IMG]https://i.hizliresim.com/DYA9jO.jpg[/IMG]


    [IMG]https://i.hizliresim.com/Em0pjA.jpg[/IMG]


    [IMG]https://i.hizliresim.com/jgDjdr.jpg[/IMG]


    [IMG]https://i.hizliresim.com/26l5pq.jpg[/IMG]
    Last edited by Uwe; 03-09-2019 at 06:13 PM. Reason: Added NOPARSE tags because images don't display even when going to the URLs directly

  6. #6
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    any comments?

  7. #7
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    How long has it been running the same coolant before you changed it and what did it look like at the time of changing? If the answer is ‘since it rolled out the factory’ and ‘like sh*t’, my follow-up question would be: what does the water pump and especially the vanes look like?
    Current:
    2018 Tiguan AD Highline 2.0 BiTDI 240hp > Stage 1+ 328hp
    2016 Polo 6C Highline 1.0 TSI 105hp

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