Temperature issue
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Temperature issue
Turning to the forum family for this one.. so I've been having a problem with my 01 A4 Quattro, at least I think it's a problem. What's been happening is that after driving, I shut my car off and when I turn it on after a minute or so, the temperature gauge needle moves up to the first line. I first noticed this while I was driving my car, I noticed that the needle would go smack dab in the middle and it slowly climbed up a little but then would move back down as I started driving. I took it to the mechanic who replaced my timing belt and they replaced the coolant temp sensor and thermostat (again). Now, the needle would sit a tad on the cool side while driving, sometimes it would move directly to the middle but nothing towards the hot side.
But when I would turn the car off and just turn it to the on position after it reaches operating temperature, the needle is back at the first line on the hot side. So I took it to another shop and they said my cooling system pressure is 70 PSI. They said I either have a cracked cylinder head or blown head gasket (it shouldn't be since the first shop replaced it). The first shop said they ran pressure tests overnight and they say the pressures aren't high. So idk what it could be..
Is it normal for the temp needle to go up (240 F) while the car is off then back to normal (190 F) when I start the engine and begin driving? And if not, could it be from a cracked head or head gasket not properly sealed? I also noticed that the overflow hose to the top of the coolant reservoir starts bubbling in the reservoir and the reservoir gets pretty hot too.
But when I would turn the car off and just turn it to the on position after it reaches operating temperature, the needle is back at the first line on the hot side. So I took it to another shop and they said my cooling system pressure is 70 PSI. They said I either have a cracked cylinder head or blown head gasket (it shouldn't be since the first shop replaced it). The first shop said they ran pressure tests overnight and they say the pressures aren't high. So idk what it could be..
Is it normal for the temp needle to go up (240 F) while the car is off then back to normal (190 F) when I start the engine and begin driving? And if not, could it be from a cracked head or head gasket not properly sealed? I also noticed that the overflow hose to the top of the coolant reservoir starts bubbling in the reservoir and the reservoir gets pretty hot too.
Last edited by jordankyle; Feb 28, 2017 at 05:17 PM.
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Joined: Nov 2012
Posts: 333
From: Aus, Sydney
From personal experience the needle going above the 90 degrees Celsius is normal if the car is switched off and then turned on shortly after however I believe it depends on outside temperature. For example a few weeks ago it was like 42 degrees Celsius here in Sydney and driving my coolant temp was 90 right in the middle. I switch the car off and about 20-30 min later when I went to drive it again it was a tad over 90. This I believe was because of the heat outside and once the car is switched off the coolant just remains sitting there in its own heat. Given enough time if the car was left off it would have obviously dropped below 90. Also note as soon as I started driving the temp moved back to 90 as the coolant started flowing through again which is what you also described. I would assume this is all normal under very hot conditions. I would assume that this may also be caused by hard driving for a period of time where you really push the car for say 20 min and have it switched off shortly after. The car needs some time to circulate the coolant and if switched off soon after may also cause the raise in temp.
If hot conditions are not the cause along with some hard driving then I am not sure :/ may have to wait for someone else to weigh in on it, good luck.
Regards,
George
If hot conditions are not the cause along with some hard driving then I am not sure :/ may have to wait for someone else to weigh in on it, good luck.
Regards,
George
Last edited by george1546; Mar 4, 2017 at 05:38 PM.
Thread Starter
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Joined: Feb 2017
Posts: 16
From personal experience the needle going above the 90 degrees Celsius is normal if the car is switched off and then turned on shortly after however I believe it depends on outside temperature. For example a few weeks ago it was like 42 degrees Celsius here in Sydney and driving my coolant temp was 90 right in the middle. I switch the car off and about 20-30 min later when I went to drive it again it was a tad over 90. This I believe was because of the heat outside and once the car is switched off the coolant just remains sitting there in its own heat. Given enough time if the car was left off it would have obviously dropped below 90. Also note as soon as I started driving the temp moved back to 90 as the coolant started flowing through again which is what you also described. I would assume this is all normal under very hot conditions. I would assume that this may also be caused by hard driving for a period of time where you really push the car for say 20 min and have it switched off shortly after. The car needs some time to circulate the coolant and if switched off soon after may also cause the raise in temp.
If hot conditions are not the cause along with some hard driving then I am not sure :/ may have to wait for someone else to weigh in on it, good luck.
Regards,
George
If hot conditions are not the cause along with some hard driving then I am not sure :/ may have to wait for someone else to weigh in on it, good luck.
Regards,
George
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Joined: Nov 2012
Posts: 333
From: Aus, Sydney
Have a look at your overflow tank once the temp gets above 90c, if it has leaked from overflow than it is prob safe to assume that car may be overheating. From reading a little online a radiator clogged due to mineral deposits may work just fine without the ac on and will show no signs of the car over heating however switching the ac on having the compressor on causes extra load which can cause it to saturate the coolant with heat. It is also a good idea to check for a stuck thermal stat and go from here.
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Joined: Feb 2017
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Have a look at your overflow tank once the temp gets above 90c, if it has leaked from overflow than it is prob safe to assume that car may be overheating. From reading a little online a radiator clogged due to mineral deposits may work just fine without the ac on and will show no signs of the car over heating however switching the ac on having the compressor on causes extra load which can cause it to saturate the coolant with heat. It is also a good idea to check for a stuck thermal stat and go from here.
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Joined: Mar 2010
Posts: 194
I have a 97 FWD V6 2.8 AFC engine. My does the same. If I drive it - it runs normal temp. However if I turn it off after driving and then turn it back on shortly after the temp rises above the middle mark until the engine appears to allow the coolant to flow again.
I recently replaced the fan clutch, coolant flush new expansion tank and cap. I think the thermostat is fine only because it reached operating temp in about 4-5 minutes and stays there. Last summer - before I changed the items above it would run hot (the first hash to hash-1/2) above the middle when sitting/driving in traffic at outside temp above 105 F. So when it heats up this summer I will see of all is okay or if I need to check for other problems.
Thanks for the feedback on the coolant tank and radiator. I am new to this so not sure, but with regards to head gasket I had an issue (eventually blow) head gasket with a different car and the temp gauge issue was not like now at all. With the blown head gasket the gauge would swing from cold to hot to normal.. it was all over the place and very random.. unlike turning the car off then back on shortly thereafter.
I recently replaced the fan clutch, coolant flush new expansion tank and cap. I think the thermostat is fine only because it reached operating temp in about 4-5 minutes and stays there. Last summer - before I changed the items above it would run hot (the first hash to hash-1/2) above the middle when sitting/driving in traffic at outside temp above 105 F. So when it heats up this summer I will see of all is okay or if I need to check for other problems.
Thanks for the feedback on the coolant tank and radiator. I am new to this so not sure, but with regards to head gasket I had an issue (eventually blow) head gasket with a different car and the temp gauge issue was not like now at all. With the blown head gasket the gauge would swing from cold to hot to normal.. it was all over the place and very random.. unlike turning the car off then back on shortly thereafter.
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