Coolant temp gauge suddenly reads 50% lower
09-22-2011, 09:32 PM
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Coolant temp gauge suddenly reads 50% lower
For about 2 months, my aux water pump on my 2000 A6 2.7t has been progressively leaking more and more. I topped off the coolant reservoir with approved pink Audi coolant and never let it run dry.
I changed out the aux water pump last week, and have been driving it for about 5 days with everything operating normally.
Today I noticed that the coolant temperature gauge took a long time to rise (longer than normal) and settled at about 1/8 or 1/4 of the way up while highway driving, instead of the normal 50% to 60%. When driving slowly in a parking lot or neighborhood, the temp gauge creeps up to about 40%. The first time I noticed the coolant temp gauge acting strangely, I saw it rise up to about 70% of the way to hot and then fairly quickly drop down to below 50% - as if the thermostat was opening.
The thermostat and water pump have 5000 miles on them.
Any ideas?
I changed out the aux water pump last week, and have been driving it for about 5 days with everything operating normally.
Today I noticed that the coolant temperature gauge took a long time to rise (longer than normal) and settled at about 1/8 or 1/4 of the way up while highway driving, instead of the normal 50% to 60%. When driving slowly in a parking lot or neighborhood, the temp gauge creeps up to about 40%. The first time I noticed the coolant temp gauge acting strangely, I saw it rise up to about 70% of the way to hot and then fairly quickly drop down to below 50% - as if the thermostat was opening.
The thermostat and water pump have 5000 miles on them.
Any ideas?
09-23-2011, 07:14 AM
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09-23-2011, 09:47 AM
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Who did the thermostat and water pump replacement? I assume it was done at the same time as TB replacement.
If a shop did the waterpump and thermostat get back to them...the thermostats have been known to fail.
Otherwise check the temp sensor (easy enough to replace anyway) but be prepared to replace the thermostat.
If a shop did the waterpump and thermostat get back to them...the thermostats have been known to fail.
Otherwise check the temp sensor (easy enough to replace anyway) but be prepared to replace the thermostat.
09-23-2011, 12:07 PM
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Yes, I did the t-stat and water pump at the same time as timing belt and everything else associated with that job. I hope that's not what it is because it will be on me except for Blau Parts would probably cover the thermostat cost.
I see that I have the green sensor, so will be ordering one of those today.
How much of the coolant needs to be drained to replace the sensor without spilling it all over the place?
I see that I have the green sensor, so will be ordering one of those today.
How much of the coolant needs to be drained to replace the sensor without spilling it all over the place?
09-23-2011, 12:37 PM
#6
If the coolant is not hot, you will probably lose a minimal amount when you pull the sensor. Put some paper towels around the plug to keep this down even more and replace quickly. If the coolant is even a little warm, it will come pouring out pretty quickly....don't do that.
My bet is on the CTS - I think if it was a bad thermostat, it would have to be stuck OPEN in order for your coolant temperature to be lower than normal, and even then, I think it would still be well above half of the normal temperature, but I could be wrong. If it were stuck closed, you'd have high temperature I believe, not low. Maybe I don't get how it works though...
My bet is on the CTS - I think if it was a bad thermostat, it would have to be stuck OPEN in order for your coolant temperature to be lower than normal, and even then, I think it would still be well above half of the normal temperature, but I could be wrong. If it were stuck closed, you'd have high temperature I believe, not low. Maybe I don't get how it works though...
09-23-2011, 01:19 PM
#7
Yes, I did the t-stat and water pump at the same time as timing belt and everything else associated with that job. I hope that's not what it is because it will be on me except for Blau Parts would probably cover the thermostat cost.
I see that I have the green sensor, so will be ordering one of those today.
How much of the coolant needs to be drained to replace the sensor without spilling it all over the place?
I see that I have the green sensor, so will be ordering one of those today.
How much of the coolant needs to be drained to replace the sensor without spilling it all over the place?
You might also have some air in the cooling system. Try bleeding the air out to make sure.
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09-23-2011, 02:02 PM
#8
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I agree...the purpose of opening the cap is to equalize pressure....of course, if outside air pressure is higher than inside the tank, you're giving up something. The only problem is when inside pressure is higher than outside, like when the coolant is warm.
When you pop the clip on the CTS to remove the CTS some coolant flows out until the system vacuum locks...just make sure you replace the O-ring and lube it with coolant before installing the new CTS.
You might or might not have to bleed the system after it's been run awhile due to the little bit of air that go in when you replaced the CTS.
09-23-2011, 02:25 PM
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Yes, I did the t-stat and water pump at the same time as timing belt and everything else associated with that job. I hope that's not what it is because it will be on me except for Blau Parts would probably cover the thermostat cost.
I see that I have the green sensor, so will be ordering one of those today.
How much of the coolant needs to be drained to replace the sensor without spilling it all over the place?
I see that I have the green sensor, so will be ordering one of those today.
How much of the coolant needs to be drained to replace the sensor without spilling it all over the place?
http://shop.advanceautoparts.com/web...1903258274____
I have no issues with mines so far, less than 500mi on it though.
09-23-2011, 05:54 PM
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The gauge has never passed the mid mark since that initial time when it rose above. In fact, it hovers at around 1/4 most of the time. I also suspect the CTS.
We don't have Advanced Auto around here, but I'll see if they are part of a conglomerate like Checker/ Kragen/ Schucks/ O'Reilly and maybe one of those stores has the same deal. Can't beat that! Big deal if it fails in a few years as it looks like a 5 minute job.
I'll depressurize the reservoir before removing.
Thanks!
We don't have Advanced Auto around here, but I'll see if they are part of a conglomerate like Checker/ Kragen/ Schucks/ O'Reilly and maybe one of those stores has the same deal. Can't beat that! Big deal if it fails in a few years as it looks like a 5 minute job.
I'll depressurize the reservoir before removing.
Thanks!