# Overheating Issue



## thormx353 (Dec 24, 2012)

http://forums.vwvortex.com/showthread.php?6032049-Overheating-issue 

Any ideas guys? I'm clueless at this point. I'm pulling out the new thermostat to test it and getting some radiator cleaner. Everything seems to be working except for the fact that my bottom hose never gets warm so I'm thinking it's the thermostat or radiator. Also, I tested the old thermostat (thinking it was the cause of the problem to begin with) and it worked.


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## Neb (Jan 25, 2005)

Did you check the fuses on top of the battery? They are the ones that control your fan, when I had a similar issue it turned out to just be a blown fuse.


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## thormx353 (Dec 24, 2012)

Neb said:


> Did you check the fuses on top of the battery? They are the ones that control your fan, when I had a similar issue it turned out to just be a blown fuse.


 Yeap all good. I know the fans are an issue but shouldn't be causing my car to overheat so much. For some reason my T-Stat isn't opening or coolant isn't making it's way to the lower rad hose.


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## thormx353 (Dec 24, 2012)

Can someone tell me the estimated temps that coincide with the stock gauge? Can't seem to find that information.


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## trixx (Dec 23, 2002)

thormx353 said:


> Yeap all good. I know the fans are an issue but shouldn't be causing my car to overheat so much. For some reason my T-Stat isn't opening or coolant isn't making it's way to the lower rad hose.


 check this thread... 

http://forums.vwvortex.com/showthread.php?5736399-180Q-Overheating-Fans-Turn-On&highlight=resistors 


if the low speed fans aren't kicking in, your car will over heat... a lot. 
it's most likely burnt out resistors in the low speed(s) switch inside one or both of your fan motors.


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## FullyLoadedCarat (Nov 20, 2010)

If everything worked before the t-stat/t-belt change, you could have put your thermostat in backwards. Mine had the same symptoms, fans wouldnt come on, would heat up a full tick, but was fine on the highway. Sure as heck, pulled it out thinking I had a dud, and it came out with the element not in the block. Pain in the ass to check, as you've got to take the housing off, but its a cheap first place to look!


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## hunTTsvegas (Aug 27, 2012)

FullyLoadedCarat said:


> If everything worked before the t-stat/t-belt change, you could have put your thermostat in backwards. Mine had the same symptoms, fans wouldnt come on, would heat up a full tick, but was fine on the highway. Sure as heck, pulled it out thinking I had a dud, and it came out with the element not in the block. Pain in the ass to check, as you've got to take the housing off, but its a cheap first place to look!


 One of the first things with troubleshooting symptoms is returning back to where the problems worsened and isolate from there. In the other thread, you referenced that your heat gauge would go up to halfway sometimes. That's actually normally where mine stays and everything operates perfectly. If you're exceeding that and you weren't before changing the thermostat then something suggests (at least to myself) to check the thermostat that was installed and confirm that it is the proper thermostat. I think I remember there being two different thermostat temperatures that would work with this engine (82*c and 87*c.. ?). 

In any matter, I wish you the best in finding your problem. :beer:


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## luchos (Feb 23, 2012)

I would start with the coolant temp sensor first to see if you're actually over heating, you mentioned that the gauge will go up to half (which is normal operating temp around 190F) and go back down? It's a $10 sensor and wouldn't hurt to replace even if it's good. If your car is actually over heating 99% of the time there's an issue with the water pump. It's the most common cooling system failure on a 1.8t.


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## thormx353 (Dec 24, 2012)

luchos said:


> I would start with the coolant temp sensor first to see if you're actually over heating, you mentioned that the gauge will go up to half (which is normal operating temp around 190F) and go back down? It's a $10 sensor and wouldn't hurt to replace even if it's good. If your car is actually over heating 99% of the time there's an issue with the water pump. It's the most common cooling system failure on a 1.8t.


 
Please refer to the link at the top of the thread. Water pump, thermostat, and coolant temp sensor have all been replaced. I replaced the water pump thinking it would solve the problem when in fact it didn't do anything at all so I know it's not that.


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## luchos (Feb 23, 2012)

thormx353 said:


> Please refer to the link at the top of the thread. Water pump, thermostat, and coolant temp sensor have all been replaced. I replaced the water pump thinking it would solve the problem when in fact it didn't do anything at all so I know it's not that.


my bad:banghead: i'd say check the relay and fuses if the fan does not kick on


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## FullyLoadedCarat (Nov 20, 2010)

hunTTsvegas said:


> One of the first things with troubleshooting symptoms is returning back to where the problems worsened and isolate from there. In the other thread, you referenced that your heat gauge would go up to halfway sometimes. That's actually normally where mine stays and everything operates perfectly. If you're exceeding that and you weren't before changing the thermostat then something suggests (at least to myself) to check the thermostat that was installed and confirm that it is the proper thermostat. I think I remember there being two different thermostat temperatures that would work with this engine (82*c and 87*c.. ?).
> 
> In any matter, I wish you the best in finding your problem. :beer:


Totally right on that mang, went back to the initial problem for the answer. First thermostat was toast.

Second time around the thermostat was backwards. *Having it backwards creates many of the same symptoms of burnt out fans and relays*. It's in a terrible spot to reach if you don't take the alt off, so its easy to put in wrong if you're not paying attention like I wasn't. I chased my tail for days thinking it was fuses/relays/ and dead fans, so I pulled the t-stat, just to be sure. Cost me a couple hours and some extra coolant to figure it out. Popped in an 82 degree and called it a day. :beer:


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## peter139 (May 4, 2005)

Nice to see you solved your problem. 

With the thermostat backwards the system don't work.


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## thormx353 (Dec 24, 2012)

Got the problem worked out...almost. My lower rad hose wasn't getting cold so I aggressively bled the system even more to try and get some coolant flowing through it. Seemed to work because the lower rad hose now gets warm. I also just found out last night you can check the coolant temp through the HVAC controls...I'm usually between 92-98C which seems to be a few degrees higher than ideal considering it has been 60ish outside when I was testing it. My main issue now is my larger radiator fan not working. When I turn the heat/ac on only the little fan kicks on. I can't remember for sure (I'm at work so I'll have to double check when I get home) but when pulled #16 fuse I believe only the little fan was on. I was thinking either the radiator fan switch or the fan itself as the problem. Thoughts?


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## 20v master (May 7, 2009)

thormx353 said:


> I'm usually between 92-98C which seems to be a few degrees higher than ideal considering it has been 60ish outside when I was testing it.


Way too hot! My peak at a track day this past week was 104*C, and that's still too high for racing. You should be within 1-2* of your thermostat, so if you have an 87*C Tstat, you'd see ~90*C coolant temps at idle/in traffic once warmed up. Have you checked the fan control module? They are a common failure point also.


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## thormx353 (Dec 24, 2012)

20v master said:


> Way too hot! My peak at a track day this past week was 104*C, and that's still too high for racing. You should be within 1-2* of your thermostat, so if you have an 87*C Tstat, you'd see ~90*C coolant temps at idle/in traffic once warmed up. Have you checked the fan control module? They are a common failure point also.



I'm going to test for power to the fans tonight. I checked all the fuses already and they are good. If I'm getting this right....no power to fan = bad FCM......If there is power to fan = bad fan. Correct? I'm going to order a new fan switch either way because they are so cheap.


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## 20v master (May 7, 2009)

thormx353 said:


> I'm going to test for power to the fans tonight. I checked all the fuses already and they are good. If I'm getting this right....no power to fan = bad FCM......If there is power to fan = bad fan. Correct? I'm going to order a new fan switch either way because they are so cheap.


Correct. You can run 12v hot straight to the fan to see if it works.


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## thormx353 (Dec 24, 2012)

20v master said:


> Correct. You can run 12v hot straight to the fan to see if it works.


Fan is getting power. Ordering a new one tonight.


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## thormx353 (Dec 24, 2012)

UPDATE: Replaced the main fan today. Before the passenger side fan would kick on when the a/c or heat was on and does not now at all. The big fan kicks on intermittently from start up (comes on for 5 seconds, goes off for another 30 seconds or so and kicks back on.) Temps are still the same and haven't gone down, but I don't think the fan is kicking on long enough to make a difference. Checked all the fuses as well. The only two items I haven't replaced yet is the fan switch and FCM. I'd rather not dump any more unnecessary money into this if possible. Any ideas?


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## thormx353 (Dec 24, 2012)

thormx353 said:


> UPDATE: Replaced the main fan today. Before the passenger side fan would kick on when the a/c or heat was on and does not now at all. The big fan kicks on intermittently from start up (comes on for 5 seconds, goes off for another 30 seconds or so and kicks back on.) Temps are still the same and haven't gone down, but I don't think the fan is kicking on long enough to make a difference. Checked all the fuses as well. The only two items I haven't replaced yet is the fan switch and FCM. I'd rather not dump any more unnecessary money into this if possible. Any ideas?


After posting this I realized my lower radiator hose isn't getting warm. Replaced within the last 5k- water pump,CTS, thermostat, and primary fan. I'm thinking the radiator is my enemy right now. Only reason why there isn't coolant flowing through it.


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## lite1979 (Sep 9, 2005)

Actually, with the thermostat closed, your radiator won't have water moving through it, so the lower hose should be cool until the coolant in the loop without the radiator reaches 90 degrees celsius or so, then coolant should start to make its way past the thermostat from the radiator, but even then, it'll take a while for that lower hose to get hot if you're just idling. With no thermostat in my car at all, it took a good twenty minutes before the coolant got to 90 C, and then it took another five minutes at that temp before the radiator fan came on. This was after I replaced my radiator.

My radiator got clogged after my head gasket went bad, but I don't see you mentioning that anywhere in this thread. Have you mixed G12 with any other coolant in your efforts to troubleshoot? There's a lot more than just oil that can clog it up. I determined mine was bad with a simple effort of trying to blow air through it after I drained the system.


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## toy4two2 (Feb 6, 2012)

20v master said:


> Way too hot! My peak at a track day this past week was 104*C, and that's still too high for racing. You should be within 1-2* of your thermostat, so if you have an 87*C Tstat, you'd see ~90*C coolant temps at idle/in traffic once warmed up. Have you checked the fan control module? They are a common failure point also.


I don't think that it is too high for OP's car

I normally run at 91*C. The hottest I ever got it was 110*C racing up Palomar Mountain at WOT for about 7 miles. It did cool down pretty quickly when I stopped and let it idle to take in the view.

My cooling system is in tip top shape.

One other thing, if he runs a metal impeller water pump 3 degrees hotter is normal (94 degrees).


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## 20v master (May 7, 2009)

toy4two2 said:


> I don't think that it is too high for OP's car
> 
> My cooling system is in tip top shape.
> 
> One other thing, if he runs a metal impeller water pump 3 degrees hotter is normal (94 degrees).


What makes you think it's not too high? How are you defining "tip top shape?" And why do you think a metal impeller pump automatically adds 3" to coolant temps? Seems like a lot of assumptions going on that need to be verified before accepting any of this info as factual. It may not be too hot so as to cause damage, but it sure isn't helping performance.


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## thormx353 (Dec 24, 2012)

Cruising the temps hover from 89 to 94. I was in a parking lot today and it got up to 98 with steam coming off my radiator. Something is telling my radiator is not flowing enough coolant to sufficiently cool the engine. The fan I installed only comes on when the car is first started every 30 seconds or so, then doesn't come on at all. Thinking radiator, fan switch, or FCM.


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## 20v master (May 7, 2009)

Is your AC working? Fans come on with AC and it's blowing cold? If not, then it's your fan control module.


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## thormx353 (Dec 24, 2012)

20v master said:


> Is your AC working? Fans come on with AC and it's blowing cold? If not, then it's your fan control module.


AC blows very cold, fans do not kick on. I'll look into an FCM next.


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## lite1979 (Sep 9, 2005)

Check your after-run coolant pump for any signs of leakage. I'm also thinking you could have a clogged radiator, though. Even though your t-stat is opening up, it sounds like coolant isn't making it to the temp sensor in the radiator to turn the fans on. Mine did the same thing when it was clogged. Drain the system, disconnect the hoses, and try to blow air through the radiator. It should be as easy as blowing air through a paper towel tube.


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## thormx353 (Dec 24, 2012)

lite1979 said:


> Check your after-run coolant pump for any signs of leakage.


First time hearing about such a thing.




lite1979 said:


> I'm also thinking you could have a clogged radiator, though. Even though your t-stat is opening up, it sounds like coolant isn't making it to the temp sensor in the radiator to turn the fans on. Mine did the same thing when it was clogged. Drain the system, disconnect the hoses, and try to blow air through the radiator. It should be as easy as blowing air through a paper towel tube.


I'm thinking clogged radiator as well.


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## fresh1 (Aug 29, 2004)

I have seen 1.8t water pumps fail. Last one I replaced, I found the impeller broken off. Have seen t-stats problems also. My tt gauge started to show it was overheating and it turned out my cluster was on its way out. Replacing it cured my false overheating readings. Head gasket failures also.


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## thormx353 (Dec 24, 2012)

fresh1 said:


> I have seen 1.8t water pumps fail. Last one I replaced, I found the impeller broken off. Have seen t-stats problems also. My tt gauge started to show it was overheating and it turned out my cluster was on its way out. Replacing it cured my false overheating readings. Head gasket failures also.


Has a new water pump. Thinking radiator and FCM then onto head gasket if those don't work.


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## toy4two2 (Feb 6, 2012)

A fellow named Wak, who I consider the ultimate expert on the MKI TT, did the testing showing the metal water pump ran three degrees hotter then plastic and he switched back to plastic. 

I say I'm in tip top because I have two week old g12, new water pump in plastic, all hoses replaced, new coolant temp sensor, refurbished dash pod, 2 month old thermostat, new coolant tank and tank cap. System was flushed with water all fans work and come on at proper times and after run pump works. I also mix 60/40 water to coolant since I live in So Cal.

I also regularly Vagcom scan my car....trust me I'm tip top and average 91*c. 

Sent from my SGH-T989 using Tapatalk 2


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## lite1979 (Sep 9, 2005)

thormx353 said:


> First time hearing about such a thing.


Google it and you'll see plenty of examples of failed after-run coolant pumps.

I would just check it to be safe. It mounts to the engine side of the radiator on our cars, and on mine, the plastic nipple that connects to the line going back to the turbo is what cracked. Mine may have gone prematurely since I had a head gasket failure, but after doing my water pump, t-stat, and replacing the after-run pump, my heater core blew. I bypassed that, and that's when I noticed oil in my expansion tank. I then decked the head and replaced the head gasket, and once that was done, I started to overheat and my expansion tank boiled over. Once I replaced the radiator I haven't overheated once. I actually run cooler than 90C most of the time, but I'm in Buffalo, NY.


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## FullyLoadedCarat (Nov 20, 2010)

You're 100 percent sure that t-stat is in correctly? I had all the same issues...


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## thormx353 (Dec 24, 2012)

Update: Haven't been able to get into too much the past week with life getting in the way. So far all that has been done is timing belt/water pump, t-stat, system flush, green CTS, 2.0 coilpacks, spark plugs and primary radiator fan. I have managed to keep the temps down the most part average around 93-94C and sometimes jumping up to 97-98 when the engine is under load and down to 90ish if I'm cruising. However, the past couple days have been pretty here in PA getting close to 90 degrees and I can say the TT doesn't like that too much. In fact yesterday just pulling into the parking lot for a couple minutes to pick up a friend my temp jumped up to 107 before coming back down after going down the road for a couple miles. I'm getting my Si back on the road this week so I can have some down time with the TT. I'm still voting clogged radiator or possible FCM since my primary fan acts strange. I noticed yesterday that my A/C wasn't blowing cold like before either in the hot weather.


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## FullyLoadedCarat (Nov 20, 2010)

FullyLoadedCarat said:


> *You're 100 percent sure that t-stat is in correctly? I had all the same issues...*


.


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## toy4two2 (Feb 6, 2012)

sounds like a tstat issue or maybe someone put the wrong coolant in the system and its geled up. You can take off the driver's side coolant elbow and you'll see a yellowish brown paste like substance if its got that crap in there.


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## thormx353 (Dec 24, 2012)

FullyLoadedCarat said:


> .


Yeah I installed it correctly. With the little brace part sticking out.


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## thormx353 (Dec 24, 2012)

toy4two2 said:


> sounds like a tstat issue or maybe someone put the wrong coolant in the system and its geled up. You can take off the driver's side coolant elbow and you'll see a yellowish brown paste like substance if its got that crap in there.


Not a Tstat issue. I'm thinking maybe at some point the wrong coolant was put in there gumming up the radiator. Going to replace it anyway.


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## thormx353 (Dec 24, 2012)

Forgot to mention this but thought it would be important. Changed my plugs and spark plugs a couple weeks and and I had oil on the plug threads. Valve cover, head gasket?


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## 20v master (May 7, 2009)

thormx353 said:


> Forgot to mention this but thought it would be important. Changed my plugs and spark plugs a couple weeks and and I had oil on the plug threads. Valve cover, head gasket?


Middle piece of valve cover gasket set is leaking into spark plug bores.


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## thormx353 (Dec 24, 2012)

20v master said:


> Middle piece of valve cover gasket set is leaking into spark plug bores.


Thanks I'll probably fix that while I have the car down. Getting a new radiator soon. Will update with mysterious over heating issue.


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## thormx353 (Dec 24, 2012)

Anybody know why my temp fluctuates between driving up/down hills and idling? I've seen it go up to 105 idling on a hot day. When I'm driving on a flat road or down a hill it will usually stay around 92-94 and when I'm going up a hill will go up to 97-98. I was thinking about ordering a lower temp thermostat and rad fan switch tomorrow.


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## 20v master (May 7, 2009)

Uphill = more load = boost. Our front ends have horrible airflow, plus its summer.


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## thormx353 (Dec 24, 2012)

20v master said:


> Uphill = more load = boost. Our front ends have horrible airflow, plus its summer.


 I figured. Just wanted to make sure. Thanks.


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## thormx353 (Dec 24, 2012)

Update: Thought I had the car sorted out, at least enough that I didn't have to worry. However, yesterday me and a buddy were out joy riding in the nice weather and on our way back to drop him off at his car we stopped at a gas station for 5 min and then drive down the road a couple minutes to check out another TT for sale (stopping for about another 5 min). When I came back to my car and checked the temp I was at 115c! I started driving down the road and it kept climbing to about 117 and then dropped the whole way back down to 93C, all within about a mile of driving. I'm a bit perplexed over the cause and becoming frustrated because I really like the car as my DD. I just don't trust it.


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## thormx353 (Dec 24, 2012)

thormx353 said:


> Update: Thought I had the car sorted out, at least enough that I didn't have to worry. However, yesterday me and a buddy were out joy riding in the nice weather and on our way back to drop him off at his car we stopped at a gas station for 5 min and then drive down the road a couple minutes to check out another TT for sale (stopping for about another 5 min). When I came back to my car and checked the temp I was at 115c! I started driving down the road and it kept climbing to about 117 and then dropped the whole way back down to 93C, all within about a mile of driving. I'm a bit perplexed over the cause and becoming frustrated because I really like the car as my DD. I just don't trust it.


 
I live in a fairly rural area and I'm afraid the day I go into town or the city and get stuck in traffic I'll be screwed.


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## jzobie (Jun 8, 2008)

thormx353 said:


> Update: Thought I had the car sorted out, at least enough that I didn't have to worry. However, yesterday me and a buddy were out joy riding in the nice weather and on our way back to drop him off at his car we stopped at a gas station for 5 min and then drive down the road a couple minutes to check out another TT for sale (stopping for about another 5 min). When I came back to my car and checked the temp I was at 115c! I started driving down the road and it kept climbing to about 117 and then dropped the whole way back down to 93C, all within about a mile of driving. I'm a bit perplexed over the cause and becoming frustrated because I really like the car as my DD. I just don't trust it.


 That sounds like a bad T Stat to me. For the temp to drop 24* in a mile leads me to believe that the T Stat opened and allowed coolant to start flowing. Of course it could also be a temp sensor or air in the lines but I think you covered those.


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## mdjenkins (Feb 16, 2010)

Did you ever sort out your fan? 
Is your fan kicking on?


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## thormx353 (Dec 24, 2012)

jzobie said:


> That sounds like a bad T Stat to me. For the temp to drop 24* in a mile leads me to believe that the T Stat opened and allowed coolant to start flowing. Of course it could also be a temp sensor or air in the lines but I think you covered those.


 I replaced the T Stat already and tested both the old and new one. Both were fine. I also bought a cooler T Stat that I have yet to install. Could my coolant system be slightly clogged somewhere but only shows up when the engine is idle because of the lack of pressure? Is there a way to determine if my radiator is bad? 



mdjenkins said:


> Did you ever sort out your fan?
> Is your fan kicking on?


 I actually did find a plug that was unconnected (it looked like it was connected), and it solved the issue as far as my fans not kicking on at all. I'll have to double check later when I'm out of work. I don't think a fan would cause such a drastic temp change though would it? I'm half tempted to try out a 3 core radiator.


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## mdjenkins (Feb 16, 2010)

thormx353 said:


> I actually did find a plug that was unconnected (it looked like it was connected), and it solved the issue as far as my fans not kicking on at all. I'll have to double check later when I'm out of work. I don't think a fan would cause such a drastic temp change though would it? I'm half tempted to try out a 3 core radiator.


I had trouble with over heating where it would keep climbing in temp when idle but was fine when moving. Mine was a bad fan relay switch keeping the fan off. I would believe that a problem with the fan system would cause drastic changes in temp. 

If the fan is working and the computer is getting/interpreting accurate data then looking at the coolant flow and component health would be next on my list. A cursory look at the radiator for bent fins/leaks doesn't hurt anything.


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## thormx353 (Dec 24, 2012)

So my buddy has vag-com and we decided to do some logs and look at everything we could. First off I keep getting misfire codes from a rough start up but that's for another discussion. Vag-com was reading my coolant temp about 5-6 degrees cooler than what my HVAC was saying. It would read 99-100c on the car at one point and be 95c on vag-com. Which one should I go by?


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