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Discussion Starter #1
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. :mad:

3 failed thermostats in one year... It gets me angry.

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 I understand thermostat was failed?

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

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

Group 130 Map cooling

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

Group 131 Map cooling
Blok 1: Temperature Engine outlet [°C] --> The real engine temperature
Blok 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.

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

-In the first failure, temperature gauge goes up from 90 Celcius degree to 130C. Also, engine was 125 C.
-In the second failure, temperature gauge goes up from 90C to 100C, 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. Then, fans start to run and temperature goes down to 109C. 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 94.5 C degree. but, engine temperature is 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 VAGCOM Group 33, lambda value is 10% and 17%.

What is the problem? Please help me for solving it.

Premium Member
9,738 Posts
First posts normally go in introductions else you could get a free fix and we never see you again!!!

Forum Rules and Guidelines

BFQ isn't a TDI.

Manufacturer: VW, Date(s) Used: 05/2002-05/2005, Model: Bora/Variant/4Motion, Engine Code: BFQ, 75Kw, 102PS, 1.6 Ltr, 4 Cyls

Investigate more with VAG-COM\VCDS.

Premium Member
736 Posts
remove T-stat, put it in a can full of water and put it to boil on the stove. Measure the temperature of the water and see at what temperature T-starts to open and when water cools down see when it starts to close. Use laser or manual Temperature gauge.

ECT sensor could lie to PCM,
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