A4 1,8 TS coolant temp reads low
 

Hi all,

My 2001 A4 Avant 1,8 TS (8D chassis, corresponding to B5 saloon, motor
variant AJL) used to have coolant temp at a consistent 90C (is that
192F) during suburban driving, ambient temp between 0C-10C (32F-50F)

About one month ago it started showing coolant temp at a lower temp of
86C (183F).

Oil temp has been and still is consistent at ca. 80C = 175F.

I suspect that either 1) the temperature sensor (mounted on top edge of
head, aft) may be giving a bad reading - or that 2) some thermostatic
valve is stuck, allowing 100% of all coolant to flow throught the
radiator, even if ambient temp is low.

But - on Audiworld I read articles that broken temp sensors tend to
fluctuate wildly, which mine does not do. Mine just reads low. So this
may indicate that I have something else wrong - but what?

Those of you - having a similar experience yourself - who managed to
fix this, can you pls tell me what you did?

Thanks, Robert in Gothenburg Sweden, where we're still waiting for winter.

Re: A4 1,8 TS coolant temp reads low
 

Robert wrote:
> Hi all,
>
> My 2001 A4 Avant 1,8 TS (8D chassis, corresponding to B5 saloon, motor
> variant AJL) used to have coolant temp at a consistent 90C (is that
> 192F) during suburban driving, ambient temp between 0C-10C (32F-50F)
>
> About one month ago it started showing coolant temp at a lower temp of
> 86C (183F).
>
> Oil temp has been and still is consistent at ca. 80C = 175F.
>
> I suspect that either 1) the temperature sensor (mounted on top edge of
> head, aft) may be giving a bad reading - or that 2) some thermostatic
> valve is stuck, allowing 100% of all coolant to flow throught the
> radiator, even if ambient temp is low.
>
> But - on Audiworld I read articles that broken temp sensors tend to
> fluctuate wildly, which mine does not do. Mine just reads low. So this
> may indicate that I have something else wrong - but what?
>
> Those of you - having a similar experience yourself - who managed to
> fix this, can you pls tell me what you did?
>
> Thanks, Robert in Gothenburg Sweden, where we're still waiting for winter.
>

It sounds more like a bad (open) thermostat. They respond to engine temperature
not ambient.

Changing the temp sensor is probably worth a try and is a good idea anyway as
they are prone to failure, easy to change and cheap but the thermostat is more
likely to be the problem.

Changing the thermostat is usually done when the timing belt is changed. It is a
large job and if you chose to do it be sure to have the timing belt and all
associated parts done at the same time. The parts are the cheap part of the job
and it needs to be done on or before scheduled time / distance anyway.

Re: A4 1,8 TS coolant temp reads low
 

Robert wrote:
> Hi all,
>
> My 2001 A4 Avant 1,8 TS (8D chassis, corresponding to B5 saloon, motor
> variant AJL) used to have coolant temp at a consistent 90C (is that
> 192F) during suburban driving, ambient temp between 0C-10C (32F-50F)
>
> About one month ago it started showing coolant temp at a lower temp of
> 86C (183F).
>
> Oil temp has been and still is consistent at ca. 80C = 175F.
>
> I suspect that either 1) the temperature sensor (mounted on top edge of
> head, aft) may be giving a bad reading - or that 2) some thermostatic
> valve is stuck, allowing 100% of all coolant to flow throught the
> radiator, even if ambient temp is low.
>
> But - on Audiworld I read articles that broken temp sensors tend to
> fluctuate wildly, which mine does not do. Mine just reads low. So this
> may indicate that I have something else wrong - but what?
>
> Those of you - having a similar experience yourself - who managed to
> fix this, can you pls tell me what you did?
>
> Thanks, Robert in Gothenburg Sweden, where we're still waiting for winter.
>

It sounds more like a bad (open) thermostat. They respond to engine temperature
not ambient.

Changing the temp sensor is probably worth a try and is a good idea anyway as
they are prone to failure, easy to change and cheap but the thermostat is more
likely to be the problem.

Changing the thermostat is usually done when the timing belt is changed. It is a
large job and if you chose to do it be sure to have the timing belt and all
associated parts done at the same time. The parts are the cheap part of the job
and it needs to be done on or before scheduled time / distance anyway.

Re: A4 1,8 TS coolant temp reads low
 

Robert wrote:
> Hi all,
>
> My 2001 A4 Avant 1,8 TS (8D chassis, corresponding to B5 saloon, motor
> variant AJL) used to have coolant temp at a consistent 90C (is that
> 192F) during suburban driving, ambient temp between 0C-10C (32F-50F)
>
> About one month ago it started showing coolant temp at a lower temp of
> 86C (183F).
>
> Oil temp has been and still is consistent at ca. 80C = 175F.
>
> I suspect that either 1) the temperature sensor (mounted on top edge of
> head, aft) may be giving a bad reading - or that 2) some thermostatic
> valve is stuck, allowing 100% of all coolant to flow throught the
> radiator, even if ambient temp is low.
>
> But - on Audiworld I read articles that broken temp sensors tend to
> fluctuate wildly, which mine does not do. Mine just reads low. So this
> may indicate that I have something else wrong - but what?
>
> Those of you - having a similar experience yourself - who managed to
> fix this, can you pls tell me what you did?
>
> Thanks, Robert in Gothenburg Sweden, where we're still waiting for winter.
>

It sounds more like a bad (open) thermostat. They respond to engine temperature
not ambient.

Changing the temp sensor is probably worth a try and is a good idea anyway as
they are prone to failure, easy to change and cheap but the thermostat is more
likely to be the problem.

Changing the thermostat is usually done when the timing belt is changed. It is a
large job and if you chose to do it be sure to have the timing belt and all
associated parts done at the same time. The parts are the cheap part of the job
and it needs to be done on or before scheduled time / distance anyway.

Re: A4 1,8 TS coolant temp reads low
 

Robert wrote:
> Hi all,
>
> My 2001 A4 Avant 1,8 TS (8D chassis, corresponding to B5 saloon, motor
> variant AJL) used to have coolant temp at a consistent 90C (is that
> 192F) during suburban driving, ambient temp between 0C-10C (32F-50F)
>
> About one month ago it started showing coolant temp at a lower temp of
> 86C (183F).
>
> Oil temp has been and still is consistent at ca. 80C = 175F.
>
> I suspect that either 1) the temperature sensor (mounted on top edge of
> head, aft) may be giving a bad reading - or that 2) some thermostatic
> valve is stuck, allowing 100% of all coolant to flow throught the
> radiator, even if ambient temp is low.
>
> But - on Audiworld I read articles that broken temp sensors tend to
> fluctuate wildly, which mine does not do. Mine just reads low. So this
> may indicate that I have something else wrong - but what?
>
> Those of you - having a similar experience yourself - who managed to
> fix this, can you pls tell me what you did?
>
> Thanks, Robert in Gothenburg Sweden, where we're still waiting for winter.
>

It sounds more like a bad (open) thermostat. They respond to engine temperature
not ambient.

Changing the temp sensor is probably worth a try and is a good idea anyway as
they are prone to failure, easy to change and cheap but the thermostat is more
likely to be the problem.

Changing the thermostat is usually done when the timing belt is changed. It is a
large job and if you chose to do it be sure to have the timing belt and all
associated parts done at the same time. The parts are the cheap part of the job
and it needs to be done on or before scheduled time / distance anyway.

Re: A4 1,8 TS coolant temp reads low
 

TonyJ knastet inn: :

>> Those of you - having a similar experience yourself - who managed to
>> fix this, can you pls tell me what you did?

changed thermostat

>>
>> Thanks, Robert in Gothenburg Sweden, where we're still waiting for
>> winter.
>>
>
> It sounds more like a bad (open) thermostat. They respond to engine
> temperature not ambient.

agree

>
> Changing the temp sensor is probably worth a try and is a good idea
> anyway as they are prone to failure, easy to change and cheap but the
> thermostat is more likely to be the problem.
>
> Changing the thermostat is usually done when the timing belt is changed.

.... when they also (should) change the water pump.

Changing the thermostat, is quite easy - done in 30-60 minutes.

But - changing just the thermostat alone, may be /the last nail in
the coffin/ for the water pump [if it's old], due to a higher
pressure caused by the increased temperature afterwards. And then,
if you have to replace the water pump, replace timing belt as well.


> It is a large job and if you chose to do it be sure to have the timing
> belt and all associated parts done at the same time. The parts are the
> cheap part of the job and it needs to be done on or before scheduled
> time / distance anyway.

Re: A4 1,8 TS coolant temp reads low
 

TonyJ knastet inn: :

>> Those of you - having a similar experience yourself - who managed to
>> fix this, can you pls tell me what you did?

changed thermostat

>>
>> Thanks, Robert in Gothenburg Sweden, where we're still waiting for
>> winter.
>>
>
> It sounds more like a bad (open) thermostat. They respond to engine
> temperature not ambient.

agree

>
> Changing the temp sensor is probably worth a try and is a good idea
> anyway as they are prone to failure, easy to change and cheap but the
> thermostat is more likely to be the problem.
>
> Changing the thermostat is usually done when the timing belt is changed.

.... when they also (should) change the water pump.

Changing the thermostat, is quite easy - done in 30-60 minutes.

But - changing just the thermostat alone, may be /the last nail in
the coffin/ for the water pump [if it's old], due to a higher
pressure caused by the increased temperature afterwards. And then,
if you have to replace the water pump, replace timing belt as well.


> It is a large job and if you chose to do it be sure to have the timing
> belt and all associated parts done at the same time. The parts are the
> cheap part of the job and it needs to be done on or before scheduled
> time / distance anyway.

Re: A4 1,8 TS coolant temp reads low
 

TonyJ knastet inn: :

>> Those of you - having a similar experience yourself - who managed to
>> fix this, can you pls tell me what you did?

changed thermostat

>>
>> Thanks, Robert in Gothenburg Sweden, where we're still waiting for
>> winter.
>>
>
> It sounds more like a bad (open) thermostat. They respond to engine
> temperature not ambient.

agree

>
> Changing the temp sensor is probably worth a try and is a good idea
> anyway as they are prone to failure, easy to change and cheap but the
> thermostat is more likely to be the problem.
>
> Changing the thermostat is usually done when the timing belt is changed.

.... when they also (should) change the water pump.

Changing the thermostat, is quite easy - done in 30-60 minutes.

But - changing just the thermostat alone, may be /the last nail in
the coffin/ for the water pump [if it's old], due to a higher
pressure caused by the increased temperature afterwards. And then,
if you have to replace the water pump, replace timing belt as well.


> It is a large job and if you chose to do it be sure to have the timing
> belt and all associated parts done at the same time. The parts are the
> cheap part of the job and it needs to be done on or before scheduled
> time / distance anyway.

Re: A4 1,8 TS coolant temp reads low
 

TonyJ knastet inn: :

>> Those of you - having a similar experience yourself - who managed to
>> fix this, can you pls tell me what you did?

changed thermostat

>>
>> Thanks, Robert in Gothenburg Sweden, where we're still waiting for
>> winter.
>>
>
> It sounds more like a bad (open) thermostat. They respond to engine
> temperature not ambient.

agree

>
> Changing the temp sensor is probably worth a try and is a good idea
> anyway as they are prone to failure, easy to change and cheap but the
> thermostat is more likely to be the problem.
>
> Changing the thermostat is usually done when the timing belt is changed.

.... when they also (should) change the water pump.

Changing the thermostat, is quite easy - done in 30-60 minutes.

But - changing just the thermostat alone, may be /the last nail in
the coffin/ for the water pump [if it's old], due to a higher
pressure caused by the increased temperature afterwards. And then,
if you have to replace the water pump, replace timing belt as well.


> It is a large job and if you chose to do it be sure to have the timing
> belt and all associated parts done at the same time. The parts are the
> cheap part of the job and it needs to be done on or before scheduled
> time / distance anyway.

Re: A4 1,8 TS coolant temp reads low
 

Frank wrote:
> TonyJ knastet inn: :
>
>>> Those of you - having a similar experience yourself - who managed to
>>> fix this, can you pls tell me what you did?
>
>
> changed thermostat
>
>>>
>>> Thanks, Robert in Gothenburg Sweden, where we're still waiting for
>>> winter.
>>>
>>
>> It sounds more like a bad (open) thermostat. They respond to engine
>> temperature not ambient.
>
>
> agree
>
>>
>> Changing the temp sensor is probably worth a try and is a good idea
>> anyway as they are prone to failure, easy to change and cheap but the
>> thermostat is more likely to be the problem.
>>
>> Changing the thermostat is usually done when the timing belt is changed.
>
>
> ... when they also (should) change the water pump.
>
> Changing the thermostat, is quite easy - done in 30-60 minutes.
>
> But - changing just the thermostat alone, may be /the last nail in
> the coffin/ for the water pump [if it's old], due to a higher
> pressure caused by the increased temperature afterwards. And then,
> if you have to replace the water pump, replace timing belt as well.
>
>
>> It is a large job and if you chose to do it be sure to have the timing
>> belt and all associated parts done at the same time. The parts are the
>> cheap part of the job and it needs to be done on or before scheduled
>> time / distance anyway.
>
>

Thanks guys,

I will indeed change the temp sensor.

As far as water pump goes, I am told by my Audi indy that the water pump
on my motor variant (AJL) is *not* driven off of the timing belt, though
it seems to be a universal truth on this forum that all water pumps are.

My timing belt was changed one year ago at 110 000 km and I find myself
sleeping better at night as a result.

. . . I will nonetheless be left with a more weird problem, that the
car is very hard to start about 10-30 mins after shutoff, requiring the
starter motor to spin for ca. 15 sec before the motor starts . . . more
in another thread I will start shortly.

Cheers, Robert