# Cooling system problems '01 AMU



## becker780 (Apr 30, 2013)

Ive always had some slight fluctuations in my coolant temp but its gotten progressively worse. I put a new radiator in about 2 weeks ago. New thermostat about 3 months ago. New water pump, belt, tensioner etc on 7/25/12 (20k ago). My TT has been fluctuating between 190-210 over the last week. 

It seemed to be fine at idle up until a few days ago. It would only get hot while cruising. I backpinned at the thermo fan switch on the radiator and thought it was bad (as I knew the fans were good from bench testing when installing rad). It wasnt kicking on fans and A/C would turn on low speed. I bought a new switch and installed today. I found that its not the switch but the coolant flow through the system. 

I unplugged the harness to the switch and stuck the old switch in it, then heated it with a bic lighter until fans came on. 

I found that the lower hose (out) 








on the rad is not as hot as the upper (in)








And that the switch was not as hot as the upper (about the same as lower hose). 

This indicates poor coolant flow and the switch is not getting hot enough to close for either high or low speed. 

I let the engine get hot until they came on. The fans kicked on high speed at 221 F but temp did not go down. 








This is where I shut the car off as it was reaching dangerous temps. 

After letting it cool a bit I got in and let it got good and hot, then increased RPM to 4000 and held it there, temperature went quickly down to 190 F. 








Idle lets it start to increase again. 

When driving, the car gets too hot at cruise (210-215F) but at very high RPM goes back down to 190F. 

I think I should either check radiator for blockage (its about 2 weeks old) or pop out thermostat and check water pump by hand. Suggestions?

Sorry for the long explanation, just trying to paint the whole picture here. Thanks.


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## DerBassSpieler (May 12, 2008)

Hmm... I think your water pump could be suspect. What's it's history?


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## ejg3855 (Sep 23, 2004)

DerBassSpieler said:


> Hmm... I think your water pump could be suspect. What's it's history?



I had a similar problem, everything appeared new and good but the waterpump was failing. I pulled it out and it still appear ok, replaced and problems went away.


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## becker780 (Apr 30, 2013)

I currently have a pretty high concentration of dex-cool in it as I get the stuff free. Is anyone else running this?

I might yank the thermostat and feel the water pump quick tonight.


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## NotAVeTTe (Jan 2, 2014)

My car had similar symptoms and I had a small leak. Maybe the miniscule amount of air was to blame?

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## ejg3855 (Sep 23, 2004)

*FV-QR*

loathe dex-cool.


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## becker780 (Apr 30, 2013)

Pulled thermostat and checked it on the stove to make sure it wasnt stuck closed. It opens correctly. Looked at water pump inside. It looks broken, am I crazy? Im borrowing a cylinder camera tomorrow to get a better look. This is an iphone pic:










All of the water pumps Ive seen online have a ring over the fins like this:










Also, anyone have an opinion about this belt. Does it look 20,000 miles and 1.5 years old?


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## [email protected] (Dec 14, 2013)

I am by know means an expert anyone can confirm that 

Had similar problem tried every little thing control module for fans sensor in the radiator thermostat bleed it real well thought there was an air pocket checked water pump.

Turned out to be coolant temp sensor replaced it before I replaced thermostat because I was running cool. After thermostat replacement ran hot.

Anyways short version is overheating was caused by green top non OEM coolant sensor 

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## [email protected] (Dec 14, 2013)

O I forgot this hope it is not your problem.

Along time ago on a subaru I did not remove a.factory rubber plug from a new.radiator and it got sucked up into the coolant inlet lucky for me.a.coat hanger fixed this

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## lite1979 (Sep 9, 2005)

I'd say waterpump, too. Normally, I'll have someone rev the engine while I'm watching the reservoir to see if it's pushing coolant accordingly. It depends on how well you can see into the reservoir, however. Your timing belt looks fine to me, but if you're going to remove your motor mount anyway, you may as well replace it. I've never used Dex-Cool in my car before, but I've heard bad things about mixing it with G12.


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## DerBassSpieler (May 12, 2008)

If you use dex cool, use it exclusively, not mixing it with factory coolants. Mixing coolants is something to avoid in general. Napa sells pentosin products, which is the OEM stuff.


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## rstolz (Jun 16, 2009)

coolant flange off the block on the trans side is known to crack and vent, causing air pockets and blockages.

metal impeller pumps won't have the ring around the fins.

Reach in through the ermostat housing and try to spin the impeller, if it does, it's seperated from the splines.

These cooling systems are notoriously hard to bleed due to a small pump and hose diameters that far exceed the impeller diameter, and hoses that sit higher than the reservoir.

The temp sesnors and O-rings are prone to failure and poor readings, but a bad temp sesnor will not affect reading from a heat gun, only what the ECU reports.

My guess is a venting flange or a pesky air pocket, but I'd check the pump for good measure. My favorite method for bleeding these is to:
1. remove upper rad hose
2. pour coolant directly into the radiator
3. pour coolant directly into the hose
4. reattach upper rad hose
5. remove upper heater core hose
6. pour coolant into heater core
7. pour coolant into heater core hose
8. reattach heater core hose
9. proceed to bleed as normal.

takes about 15 minutes instead of burping hoses for 3 hours.

Oh, if it is the flange it's best to inspect it while the car is running and hot, and look for venting steam. You won't be able to see the hairline cracks just looking at it cold.


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## Ballysto (Oct 31, 2013)

rstolz said:


> coolant flange off the block on the trans side is known to crack and vent, causing air pockets and blockages.
> 
> metal impeller pumps won't have the ring around the fins.
> 
> ...



+1 on the coolant flange, mine started as a small crack just intermittently giving me temperature problems, but then one hot summer day it developed into a much larger crack venting and leaking out all my coolant. Only local place I could find one was at NAPA, just in case you need one.


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## becker780 (Apr 30, 2013)

Flange is good. I popped the thermostat out and stovetop tested it, its good. I checked the water pump and it does not spin on the splines (checked this when engine was cold). There are no leaks anywhere in the system, I put a cooling system pressure tester in the reservoir and it held 15 PSI for over 20 minutes (cold). 

I hooked everything back up, filled the rad and hose with 59/59 dexcool and reinstalled. Then filled the res a few times while burping hoses and got air out of almost everywhere. The auxiliary water pump bolted to the rad doesnt have coolant flow at all and the hoses to it stay pretty cold. 

If I let it idle, it will overheat. If I hop in and hold it at 3500 rpm, it cools down very fast. Idle will let it quickly heat back up. The hose connecting the thermo housing to the rad doesnt really get hot unless rpms are up. I think the water pump impeller is slipping when hot. 

Im going to try to measure coolant flow/volume with a kit tomorrow at school. If I cant theres an indy audi/vw shop down the road that will surely provide some insight.


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## DerBassSpieler (May 12, 2008)

I have an idea... Just don't ever idle! Forget all traffic signals and keep it pinned at all times. Problem solved!


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## rstolz (Jun 16, 2009)

if you have no leaks and its still not circulating, then either your t-stat is stuck closed or you have an air bubble.

as stated above these engines' cooling system is horribly designed, take the few minutes to pop off the hoses and poor coolant directly into the engine and heater core...


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## becker780 (Apr 30, 2013)

Today I ran it with the reservoir cap unscrewed. It didnt seem to take anymore coolant and it wasnt overheating at all! I stopped by Napa and got a new cap and it seems perfect. Not sure what the problem was with the old one. Wouldnt vent maybe?

I thought it wasnt flowing coolant because I didnt realize the lower rad hose was the cold side of the system. Never realized it before but coolant flows out the bottom of the rad to the tstat. It bypasses unless the coolant behind the tstat is hot enough to open and let cool water into the block. 

Maybe I had a small air bubble behind the tstat


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## Marcus_Aurelius (Mar 1, 2012)

becker780 said:


> Maybe I had a small air bubble behind the tstat


Everything you posted points out to an air pocket. Hopefully you got it all out, sometimes you need to lift the front end (standard floor ramp height is good) and rev it to a good 3k for a few minutes to build pressure and move things around. A good indication that you burped air would be lower coolant level afterward.


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## becker780 (Apr 30, 2013)

Refilled system with an airvac kit yesterday. Temp still fluctuates sometimes. Found the afterrun coolant pump was dead so I ordered one from ecs. Next step may be to throw a temp sensor in it


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