# Engine will not circulate coolant through radiator...?



## Cvrt7.62Ghst (Apr 28, 2009)

Anybody know what is at fault here? My 1990 Jetta Carat 1.8 isn't circulating fluid through the radiator, just round and round through the engine and the heater core until it overheats. I just installed a new heater core, as the old one ruptured at the start of this problem. I flushed the system, and put in new coolant. Is this a thermostat problem or a temp gauge problem?


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## Schaef (Jan 26, 2008)

*Re: Engine will not circulate coolant through radiator...? (Cvrt7.62Ghst)*

An air pocket in the coolant system can cause this http://****************.com/smile/emthup.gif Make sure you bleed all the air out by running your car with the expansion tank cap off for a bit. http://****************.com/smile/emthup.gif


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## Cvrt7.62Ghst (Apr 28, 2009)

*Re: Engine will not circulate coolant through radiator...? (Schaef)*

I did that and squeezed all the air out of the system that I could. I should also mention that the top radiator hose is warm, but not as warm as the heater core hoses, and the bottom radiator hose is cold.


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## stuston (Nov 1, 2006)

*Re: Engine will not circulate coolant through radiator...? (Cvrt7.62Ghst)*


_Quote, originally posted by *Cvrt7.62Ghst* »_I did that and squeezed all the air out of the system that I could. I should also mention that the top radiator hose is warm, but not as warm as the heater core hoses, and the bottom radiator hose is cold.

That sounds like a thermostat.


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## helicfii (Apr 15, 2009)

*Re: Engine will not circulate coolant through radiator...? (stuston)*

Replace the thermostat and your problem should go away. 
Other possibilities: 
Blocked hose, air in cooling system, water pump impeller has come loose (rare), loose or missing water pump belt, clogged radiator (you didn't pour anything funny into your cooling system, did you?) 
Sounds like a dead thermostat to me.
Whoops- missed the mention of a blown heater core. I will have to agree that there is a good chance that you are pushing combustion gases into your cooling system. That said, the whole problem may have begun with a stuck thermostat which led to over heating, which led to cylinder head warpage or a blown head gasket. I have had a thermostat freeze-up in the "closed" position, but that was after they put the head in an oven to press new valve guides in, and forgot to remove the thermostat (heat ruined it). Good luck. 


_Modified by helicfii at 2:07 PM 4-30-2009_


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## OLDSKOOLVWS (May 12, 2004)

Thermostat is stuck closed.
Get a new one. Also drill a 1/8" hole in the metal part of the flange of the the thermostat to eliminate air bubble pockets.


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## GLgod (Aug 23, 2006)

_Quote, originally posted by *Cvrt7.62Ghst* »_Anybody know what is at fault here? My 1990 Jetta Carat 1.8 isn't circulating fluid through the radiator, just round and round through the engine and the heater core until it overheats. I just installed a new heater core, as the old one ruptured at the start of this problem. I flushed the system, and put in new coolant. Is this a thermostat problem or a temp gauge problem?

Honestly, I doubt its your thermostat or air bubbles... The air bubbles will work there way out over time, so if its not getting any better there is something else thats wrong.
Check the thermostat, but they usually get stuck open, not closed...
Am I to understand that the overheating problem caused the heater core to blow? If this is the case im willing to bet its your head gasket. Overtime it breaks down any clogs the coolant passages of the head and block... Since the bottom rad hose is cool that means the engine is blocking the flow of the coolant, not allowing it to flow back to the radiator... 
Unfortunately its a VERY common sign of a blown head gasket and potential cracked head











_Modified by GLgod at 1:49 PM 4-30-2009_


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## jorge r (Apr 27, 2006)

*Re: (OLDSKOOLVWS)*


_Quote, originally posted by *OLDSKOOLVWS* »_
drill a 1/8" hole in the metal part of the flange of the the thermostat to eliminate air bubble pockets.









Look at you... brilliant, I'll remember that next time I get in there with a new 'stat. I'm taking note of this, it will help me when flushing out the system.
If there is not enough coolant, coolant will not go into the radiator no matter how open or closed the thermostat is and the result is overheating. Thermostat is fail safe open. You will notice after it the engien cools off that the coolant jug level has gone down, refill it, takes about three times before it stays leveled.
Another thing to look for is the head steam hole and hose. The top of the head has a small hose connected and that hole in the head can plug up causing steam to get trapped in there, I cleared mine by poking a guitar wire string in there.

_Modified by jorge r at 9:43 AM 5-2-2009_


_Modified by jorge r at 9:46 AM 5-2-2009_


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## OrangeDUB (Sep 18, 2006)

*Re: (jorge r)*


_Quote, originally posted by *jorge r* »_








Look at you... brilliant, I'll remember that next time I get in there with a new 'stat. I'm taking note of this, it will help me when flushing out the system.
If there is not enough coolant, coolant will not go into the radiator no matter how open or closed the thermostat is and the result is overheating. Thermostat is fail safe open. You will notice after it the engien cools off that the coolant jug level has gone down, refill it, takes about three times before it stays leveled.
Another thing to look for is the head steam hole and hose. The top of the head has a small hose connected and that hole in the head can plug up causing steam to get trapped in there, I cleared mine by poking a guitar wire string in there.

_Modified by jorge r at 9:43 AM 5-2-2009_

_Modified by jorge r at 9:46 AM 5-2-2009_

I am having the same problem with my 8v ABA after I installed a new waterpump and thermostat (for maintenance along with t-belt, tensioner, serp, v-belt, etc.). The P.O. Used that stop leak crap and the old coolant was brown and glittery. 
I am not getting circulation. It's either stuck thermostat (brand new mind you) or clogs from stop leak, or air. I can't put in much coolant. Like 1/3 gal at first. I think I have worked more in but my car is still overheating.
Where is this steam holse? The small one that goes to the exp tank?


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## OrangeDUB (Sep 18, 2006)

*FV-QR*

Got mine figured out. Had to work the air out of the uppermost rad hose with the engine off so I could hear what's going on with it. That's the spot where air gets trapped and will cause your system to not recirculate. Hope this helps someone that was in my shoes


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