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Discussion Starter · #1 ·
I may be having 2 problems, not sure.

First was the coolant light comes on randomly. Replaced water pump (with timing belt), replaced coolant, and replaced reservoir, light still flashes. Sometimes I can drive for hours, no problem, sometimes in the middle of a trip. blink, blink, blink.... Coolant level good, no codes. :evil:

One thing I have recently noticed is that the radiator fan cycles on a off. 30 seconds on, 30 seconds off. Stays on for about 30 seconds after I turn off the car. 0 degrees outside, fan still fires up on a cold car, makes a lot of noise because it is running full speed. Engine temperature gauge works normally, moves slowly up to normal temp, then stops. No overheating, no codes.

First a question. For the engine temp gauge, is that that same sensor as what is used to turn on the fan?

Could this be the aux water pump, coolant temp sensor, something else?

I don't have a wiring diagram, so I don't know what turns the fan on.

Any help would be appreciated.

Thanks
 

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The coolant light issue is the probe in the coolant ball. They are crap when it's cold out. Every morning when it's could out mine blinks and beeps. I just turnbthe car off and restart it and it's fine. Some say you can add more coolant and it helps. As far as the fan, I would replace the fan switch. It should be on the radiator. If you have access to vagcom that would tell you more. A lot of times little quirks won't throw a cel. But will show up in vagcom.
 

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Mine has the same coolant light issue... but it's an 01. Not every morning but most of the cold ones. Only thing that sucks is when it goes off I still usually check just to be safe haha.
 

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Discussion Starter · #4 ·
Ok, I am making some progress. Found a guy with a vagcom and ran diagnostics, here is what I got:

008581 - Engine Coolant Temp Sensor on Radiator Outlet (G83)
P2185 - 002 - Signal too High
Freeze Frame:
Fault Status: 01100010
Fault Priority: 2
Fault Frequency: 13
Reset counter: 255
Mileage: 171819 km
Time Indication: 0
Date: 2000.00.00
Time: 17:19:32

Freeze Frame:
RPM: 881 /min
Load: 39.6 %
Speed: 3.0 km/h
Temperature: 15.0°C
Temperature: 0.0°C
Absolute Pres.: 950.0 mbar
Voltage: 14.224 V

Readiness: 0000 0000

Ok, so this tells me that the temp sensor on radiator outlet needs to be replaced. Should be easy, right....wrong.

Jacked up car expecting to see the sensor close to the radiator outlet, not there... followed the hose, and found it. It is between the engine and the radiator about half way up. You can barely see it under the car, and can't see it from above (even with engine cover off). I could barely touch it from under the car. So what I did was push the clip out from the bottom, which flew to never-never land (don't worry, I order 2). I am hoping I can put the new clip in from the bottom. It looks symetrical. Then, twisted and pulled the sensor out, not much fluid leaked out, hardly any. Now remember, this is still attached to the wire. I was able to push the assembly forward enough that I could work from the top. I tried to remove the connector, and the hole you put the screwdriver in, just fell off because it was brittle. I then took a tiny screwdriver and forced it in from the sensor side of the connector, and was able to push the tab away from the locking feature and got the part out. I am not going to try to replace the connector because it should latch in. Anyway, waiting for parts to arrive. In the meantime, heading to church to ask for forgiveness for the language released in my garage.
 

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Discussion Starter · #5 ·
Ok, after confession, and a lot of work, I replaced the sensor. Start up engine, same problem, fan runs fast, runs slow, runs fast, runs slow.....
That problem combined with an intermittent coolant level light makes me think is is a problem with the wiring or the controller module.
Does anyone know where I can look at schematics, or have any other ideas?
 

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Discussion Starter · #6 ·
Ok, I have replaced the G83 sensor and the fan is still cycling. Below is what I get from VAG. Engine out is 79C, which is G62, seems about right for a warm engine. Radiator out is -45C, which is G83. It looks like the ECM is still reading a bad temp.

Address 01: Engine (1K0 907 115 S)

08:47:35 Group 130: Mapped Cooling
79.0°C Coolant temp. engine outlet
-45.0°C Cooland temp. radiator outlet
Thermostat duty cycle
Result

08:47:35 Group 132: Mapped Cooling
90.0°C Coolant temperature
0.0°C Temperature difference
Heater supply potentiometer
00001101 Cooling Status

08:47:35 Group 134
-60.0°C Oil temperature
4.0°C Ambient temperature
28.0°C Intake air temperature
79.0°C Engine output temperature


08:52:54 Group 135
-45.0°C Radiator output temperature
72.2 % Duty cycle cooling fan activation 1

Couple of other things, not sure why the coolant temp is saying 90C in group 132, also group 134 has the oil temp at -60C, so that can't be right. Group 135 is the most telling, as the fan does cycle at 72%, and it looks like it is making that decision based upon the radiator being -45C. My guess is that it is going into a fail safe mode because it thinks the sensor is bad.

My cooling status is 00001101, but I am not sure what that means. It doesn't change, as the fan cycles.

I am thinking the harness is bad, or ECM is bad. Anyone else have thoughts on this?
 

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Hi Fjsingel
I have couple questions for you, the engine you have on your jetta is a TSI? if yes, you said you replaced the water pump and belt, do you happen to know if the pulley retaining bolt is a regular thread or is it a reversed left thread?
At 160,000 miles, I replaced the water pump and the belt, the pulley mounted on the shaft coming from the engine looked really shiny and kind of well polished, I was thinking of replacing it as well as the belt & pump but i was not sure of the nut thread direction. Let's just say I did not want to turn a 4 hour job into a two days nightmare by breaking the axle of the pulley or stripping the thread. Do you know the answer?
appreciated!>
 

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Discussion Starter · #8 ·
Sorry, when I meant "I" with regards to the timing belt, I meant "my check book" did the work. The timing belt is over my head. I should have said "I had" the timing belt and water pump replaced.
 

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Discussion Starter · #10 ·
I found my original problem, the cooling fan coming on all of the time, to be a wiring problem between the ECM and the temp sensor. I had a dealer run an overlay harness from the ECM to the temp sensor. The do this by replacing the pins in the connectors, which is much more reliable than a splice. Total cost $600. I still have an intermittent issue with the coolant low light flashing every once in a while. Doesn't seem mission critical, so I am going to rest up for that one.
 
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