A4 1.8T B6 overheats
04-18-2015, 11:31 PM
#1
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A4 1.8T B6 overheats
I have had a problem where the temp gauge in the car have been sitting at 0 since I baught it. The coolant temperature gets reportet properly if I connect VCDS so I think it is only the gauge that is faulty.
Lately I have also had some problems with the cooling fan as it goes to max right after I start the car, even if it is cold outside.
So I read something about another temp sensor that was located in the front lower part attached to a cooling pipe. And that sensot was contorling temp gauge and fan so I eplaced that one to yesterday.
But now the temp gauge does still not work, the fan has stopped working, only revs up to ike 20% and then stops and I also have lost the heat in the car. And when connecting VCDS I get high temperatures over 100 deg C.
Also the thin hose from the expansion gets really hot but the lower wider hose does not get hot, can it be the thermostat that have broken?
I am afraid I might have messed up when I tried to flush the cooling system, I used a hose untill I got the draining water to be clear and then connected and refilled the system. But I only got 4L in the system then it was full, but I read somewhere that it should hold 6.5L so I am afraid that there where some left and I might have used different coolingfluids so that it got sludged.
Any thoughts about my problem?
Lately I have also had some problems with the cooling fan as it goes to max right after I start the car, even if it is cold outside.
So I read something about another temp sensor that was located in the front lower part attached to a cooling pipe. And that sensot was contorling temp gauge and fan so I eplaced that one to yesterday.
But now the temp gauge does still not work, the fan has stopped working, only revs up to ike 20% and then stops and I also have lost the heat in the car. And when connecting VCDS I get high temperatures over 100 deg C.
Also the thin hose from the expansion gets really hot but the lower wider hose does not get hot, can it be the thermostat that have broken?
I am afraid I might have messed up when I tried to flush the cooling system, I used a hose untill I got the draining water to be clear and then connected and refilled the system. But I only got 4L in the system then it was full, but I read somewhere that it should hold 6.5L so I am afraid that there where some left and I might have used different coolingfluids so that it got sludged.
Any thoughts about my problem?
04-19-2015, 10:57 PM
#2
I think you have a couple of issues, so lets start with the coolant.
Was the old coolant VW/Audi pink or green? If pink, doesn't matter of G11, G12,G12+ or g13 as they are backward compatible so even if you didn't get all the old stuff out it doesn't matter. I would not be concerned with sludge just yet till you get everything else figured out.
It sounds like you also have a thermostat problem but you could just have trapped air.
Did you bleed the heater and the engine coolant after the flush and refill?
There is a bleed screw in the top water pipe right above the intake to cylinders 2 &3. If you didn't, you should and be careful, it's plastic and can snap off. (I purchased mine from ECS P/N WHT000316). There is also a metal screw for early models.
The heater also needs to be bled. From memory I just released the clamp on the hoses into the fire wall. If they are original I think one has a marking and a bleed hole in the pipe. The water needs to be hot to open the heater, which should then bleed off.
My understanding is the ECU takes information from the green temperature sensor and fan switch at the bottom of the radiator which you said you just replaced to instruct the thermostat to open. Have you replaced the main temperature sensor? If not i would be doing that next, and check the wiring in the connector has not been damaged.
If all the above looks OK, then I think you you need to look at the thermostat to be replaced but check the above first.
Was the old coolant VW/Audi pink or green? If pink, doesn't matter of G11, G12,G12+ or g13 as they are backward compatible so even if you didn't get all the old stuff out it doesn't matter. I would not be concerned with sludge just yet till you get everything else figured out.
It sounds like you also have a thermostat problem but you could just have trapped air.
Did you bleed the heater and the engine coolant after the flush and refill?
There is a bleed screw in the top water pipe right above the intake to cylinders 2 &3. If you didn't, you should and be careful, it's plastic and can snap off. (I purchased mine from ECS P/N WHT000316). There is also a metal screw for early models.
The heater also needs to be bled. From memory I just released the clamp on the hoses into the fire wall. If they are original I think one has a marking and a bleed hole in the pipe. The water needs to be hot to open the heater, which should then bleed off.
My understanding is the ECU takes information from the green temperature sensor and fan switch at the bottom of the radiator which you said you just replaced to instruct the thermostat to open. Have you replaced the main temperature sensor? If not i would be doing that next, and check the wiring in the connector has not been damaged.
If all the above looks OK, then I think you you need to look at the thermostat to be replaced but check the above first.
04-19-2015, 11:31 PM
#3
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Ok, the coolant was pink before but I ended up filling it with some generic "long life" -coolant : (1,2-etandiol 50-75%, Corrosion Inhibitor SB 1-5%) witch was also pink.
I have the metal screw on a pipe and have tried bleeding through that one, but it was strange because for a long time when I bleed it there was alot of white foam coming out of it. I will look for that other hose to. So do I have to use the throttle too when bleeding the system or can the car just idle?
And do I have to raise it in the front or somthing for all the air to get out?
I have the metal screw on a pipe and have tried bleeding through that one, but it was strange because for a long time when I bleed it there was alot of white foam coming out of it. I will look for that other hose to. So do I have to use the throttle too when bleeding the system or can the car just idle?
And do I have to raise it in the front or somthing for all the air to get out?
I think you have a couple of issues, so lets start with the coolant.
Was the old coolant VW/Audi pink or green? If pink, doesn't matter of G11, G12,G12+ or g13 as they are backward compatible so even if you didn't get all the old stuff out it doesn't matter. I would not be concerned with sludge just yet till you get everything else figured out.
It sounds like you also have a thermostat problem but you could just have trapped air.
Did you bleed the heater and the engine coolant after the flush and refill?
There is a bleed screw in the top water pipe right above the intake to cylinders 2 &3. If you didn't, you should and be careful, it's plastic and can snap off. (I purchased mine from ECS P/N WHT000316). There is also a metal screw for early models.
The heater also needs to be bled. From memory I just released the clamp on the hoses into the fire wall. If they are original I think one has a marking and a bleed hole in the pipe. The water needs to be hot to open the heater, which should then bleed off.
My understanding is the ECU takes information from the green temperature sensor and fan switch at the bottom of the radiator which you said you just replaced to instruct the thermostat to open. Have you replaced the main temperature sensor? If not i would be doing that next, and check the wiring in the connector has not been damaged.
If all the above looks OK, then I think you you need to look at the thermostat to be replaced but check the above first.
Was the old coolant VW/Audi pink or green? If pink, doesn't matter of G11, G12,G12+ or g13 as they are backward compatible so even if you didn't get all the old stuff out it doesn't matter. I would not be concerned with sludge just yet till you get everything else figured out.
It sounds like you also have a thermostat problem but you could just have trapped air.
Did you bleed the heater and the engine coolant after the flush and refill?
There is a bleed screw in the top water pipe right above the intake to cylinders 2 &3. If you didn't, you should and be careful, it's plastic and can snap off. (I purchased mine from ECS P/N WHT000316). There is also a metal screw for early models.
The heater also needs to be bled. From memory I just released the clamp on the hoses into the fire wall. If they are original I think one has a marking and a bleed hole in the pipe. The water needs to be hot to open the heater, which should then bleed off.
My understanding is the ECU takes information from the green temperature sensor and fan switch at the bottom of the radiator which you said you just replaced to instruct the thermostat to open. Have you replaced the main temperature sensor? If not i would be doing that next, and check the wiring in the connector has not been damaged.
If all the above looks OK, then I think you you need to look at the thermostat to be replaced but check the above first.
04-20-2015, 05:39 AM
#4
AudiWorld Super User
1) The symptoms you had before you replaced the "black" sensor in the lower radiator line are classic "green" sensor, i.e. gauge not functioning and fans coming on. I would replace that sensor...and get a true Audi / VW sensor, not a cheap knockoff. I understand you got a "correct" reading on the VCDS, but I am not sure of the source of the temp the ECU is sending.
2) I would also be tempted to put the old "black" sensor back in because I suspect there was not issue with it and depending on where you got the new one, may not be a suitable replacement.
3) I have never had bleeding issues with my A4. The only bit that is slow to come around is the heater, but that eventually self bleeds.
4) With those 2 sensors replaced, then come back with what the overheating symptoms are although it does sound like either the thermostat or the water pump.
2) I would also be tempted to put the old "black" sensor back in because I suspect there was not issue with it and depending on where you got the new one, may not be a suitable replacement.
3) I have never had bleeding issues with my A4. The only bit that is slow to come around is the heater, but that eventually self bleeds.
4) With those 2 sensors replaced, then come back with what the overheating symptoms are although it does sound like either the thermostat or the water pump.
Last edited by lyleswk; 04-20-2015 at 05:42 AM.
04-20-2015, 11:12 AM
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Ok, I will try to change the sensors back to original Audi sensors before trying to change the thermostat or waterpump. I can't remember but I think the green one was an original from audi but the last one I got (the one that goes in the lower front cooling pipe) was from ebay.
But in VCDS I get the temperature from the G62 sensor and that one is the green one right?
I got some change in the cooling behavior today, I bleed the cooling from the metal screw for several hours, alot of the time I just got some strange foam from the screw like ther was soap in it. I could not see if it was bubbles from inside or if the hot water just boiled out.
Some times it just stopped and no water or air came from the screw even tho it was fully open. I then re-screwed it used the throttle to get the temp up and repeted like 10 times untill I had to refill alot of coolant.
But now I have got some changed behavior, when I use the throttle the temperature rises but when it hits 99-100 degrees C (in VCDS) the fan starts and gets the temp down to like 90-95 degrees C. Before the temp did rise over 100 degrees and I had to turn the car off to prevent it from overheating, now it seems to never get over 100 degrees.
But in VCDS I get the temperature from the G62 sensor and that one is the green one right?
I got some change in the cooling behavior today, I bleed the cooling from the metal screw for several hours, alot of the time I just got some strange foam from the screw like ther was soap in it. I could not see if it was bubbles from inside or if the hot water just boiled out.
Some times it just stopped and no water or air came from the screw even tho it was fully open. I then re-screwed it used the throttle to get the temp up and repeted like 10 times untill I had to refill alot of coolant.
But now I have got some changed behavior, when I use the throttle the temperature rises but when it hits 99-100 degrees C (in VCDS) the fan starts and gets the temp down to like 90-95 degrees C. Before the temp did rise over 100 degrees and I had to turn the car off to prevent it from overheating, now it seems to never get over 100 degrees.
1) The symptoms you had before you replaced the "black" sensor in the lower radiator line are classic "green" sensor, i.e. gauge not functioning and fans coming on. I would replace that sensor...and get a true Audi / VW sensor, not a cheap knockoff. I understand you got a "correct" reading on the VCDS, but I am not sure of the source of the temp the ECU is sending.
2) I would also be tempted to put the old "black" sensor back in because I suspect there was not issue with it and depending on where you got the new one, may not be a suitable replacement.
3) I have never had bleeding issues with my A4. The only bit that is slow to come around is the heater, but that eventually self bleeds.
4) With those 2 sensors replaced, then come back with what the overheating symptoms are although it does sound like either the thermostat or the water pump.
2) I would also be tempted to put the old "black" sensor back in because I suspect there was not issue with it and depending on where you got the new one, may not be a suitable replacement.
3) I have never had bleeding issues with my A4. The only bit that is slow to come around is the heater, but that eventually self bleeds.
4) With those 2 sensors replaced, then come back with what the overheating symptoms are although it does sound like either the thermostat or the water pump.
04-20-2015, 08:13 PM
#6
This at least sounds a bit more positive.
Totally agree with lyleswk to replace the green sensor as for the reasons he stated. Check the plug and the wires for bad connections too.
The fan starting up and the temperature regulating with the fan means the black fan sensor is working. (also agree with lylsewk to use genuine or at least brand name items from reputable retailers, some advertise on ebay but you can never be sure if you are buying a 'second').
I assume by your statement the temperature is now hovering 95 +/- 5, does that mean it did not go higher? If so, that means your thermostat should be opening now so check the same hoses as before to see if they are getting hot.
If they are, I am thinking you may be getting flow through the heater which has stirred up a lot of sediment and 'crap' which is making its way up through the bleeder. I have to admit the first thought I had for 'soapy' is oil, which in turn usually means head gasket, but lets keep to getting the system working.
If the hoses after the thermostat are getting hot, turn the heater on full and confirm it's getting hot (flow). I generally try to run the engine a bit faster than idle, try to sit on about 1500 -1800 revs for a couple of minutes should bring the temperature up, open the thermostat and you should be getting hot air inside the car which should also bleed out any air from the cheater core.
The bleeder should have coolant flow within seconds, not minutes, so you may still have a blockage somewhere which probably means to flush again. (also means you were on the right track originally!).
Did the heater work before you started this ? Over on the Allroad section there are some guys that have cleaned the heater core in the car by pouring in CLR. I have never tried or had to do it, but if you think the heater may be full of gunk do a search on the site for heater core cleans. You do this before you flush again.
Totally agree with lyleswk to replace the green sensor as for the reasons he stated. Check the plug and the wires for bad connections too.
The fan starting up and the temperature regulating with the fan means the black fan sensor is working. (also agree with lylsewk to use genuine or at least brand name items from reputable retailers, some advertise on ebay but you can never be sure if you are buying a 'second').
I assume by your statement the temperature is now hovering 95 +/- 5, does that mean it did not go higher? If so, that means your thermostat should be opening now so check the same hoses as before to see if they are getting hot.
If they are, I am thinking you may be getting flow through the heater which has stirred up a lot of sediment and 'crap' which is making its way up through the bleeder. I have to admit the first thought I had for 'soapy' is oil, which in turn usually means head gasket, but lets keep to getting the system working.
If the hoses after the thermostat are getting hot, turn the heater on full and confirm it's getting hot (flow). I generally try to run the engine a bit faster than idle, try to sit on about 1500 -1800 revs for a couple of minutes should bring the temperature up, open the thermostat and you should be getting hot air inside the car which should also bleed out any air from the cheater core.
The bleeder should have coolant flow within seconds, not minutes, so you may still have a blockage somewhere which probably means to flush again. (also means you were on the right track originally!).
Did the heater work before you started this ? Over on the Allroad section there are some guys that have cleaned the heater core in the car by pouring in CLR. I have never tried or had to do it, but if you think the heater may be full of gunk do a search on the site for heater core cleans. You do this before you flush again.
04-21-2015, 08:52 AM
#7
AudiWorld Super User
yes, G62 is the green one, so maybe it's okay. I would go back to a "real" black one.
John may have been closer than me, i.e. it just needed to be bled / bleed itself. Go with his suggestion about the heater and let us know.
John may have been closer than me, i.e. it just needed to be bled / bleed itself. Go with his suggestion about the heater and let us know.
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04-21-2015, 11:41 AM
#8
AudiWorld Super User
What you need to do is use vagcom to go to the instrument cluster, and see what it sees for temp, if it sees nothing the sensor on the right rear of the engine or the wiring. Slightly possible bad solder on the board of the cluster. If it sees the input but nothing showing on the gauge, its the cluster for sure.
As far as bleeding cooling system. I have never done anything special, just open bleeder if it has it, fill till it comes out, and then drive it, if it starts getting warm just stop, turn it off, wait, and it should just gulp down the reservoir and you can fill it up. I dont get where people think air is just going to magically get trapped in these and take this excessive bleeding. If the heater doesnt work its probably just a plugged up core.
Last edited by Prospeeder; 04-21-2015 at 11:47 AM.
04-22-2015, 12:05 PM
#9
AudiWorld Super User
Bad post on my part. I wasn't trying to suggest he put a black one where the green one belongs (back of the engine). He had replaced the one in the lower coolant hose with a non-OEM "black" sensor and I was suggesting he put an OEM part there. Sorry for the confusion.
04-25-2015, 11:52 PM
#10
My experience is that if its taking more than 30 min to bleed in total time spent then its a head/head gasket issue, if air is being manufactured by the engines cooling system you will never get it bled no matter how long you mess with it.
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