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I see that but when you put the model I have into ECS it only gives me the options of thermostats without holes.
I would not worry about one having a hole and another not. That's just how they were designed for that model/engine.
 

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It's within the acceptable range. What did it show in the cluster? The dash readout usually has a 20º dead spot where it will look like 190ºF but could be anywhere from 180ºF to 200ºF. This is so it does not alarm the average driver with temp fluctuations. Did the electric aux fan kick on or the mechanical fan provide any airflow while idling?
 

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I've heard running without a thermostat can cause an engine to run richer and cause carbon buildup, in other words engines need to be hot and the thermostat only opens once it reaches that temperature for a reason. If your thermostat isn't working properly buy another one.
 

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Discussion Starter #86
I appreciate the advice but it's not about the thermostat at this point. It's about what is stopping it from opening. The original and the two new ones I've already bought don't seem to be opening so I'm led to believe it's not actually the thermostat.
 

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I just checked the manual and it says in installation instructions that "bracket of coolant thermostat must be vertical". (Is that the sliver ridge of metal on the face that they mean?) I just recently installed one in mine earlier this year and I don't even think I did that, I didn't have the Bentley at that time. I was using the Haynes manual but I forget what it said.
 

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Discussion Starter #90
The Haynes doesn't say anything about that but that's how I installed it. Makes no sense really but I did it anyways.
 

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199 is pretty warm for no thermostat, but I have not tried it on the Passat. Most cars run on the cooler side without one, usually 140-160, but that is with driving not just idle. Did you try to stop the mechanical fan with a gloved hand? If it's faulty, it will stop easily. If it's hard to stop, it's good.
 

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Discussion Starter #92
199 is pretty warm for no thermostat, but I have not tried it on the Passat. Most cars run on the cooler side without one, usually 140-160, but that is with driving not just idle. Did you try to stop the mechanical fan with a gloved hand? If it's faulty, it will stop easily. If it's hard to stop, it's good.
I did not yet. I'll do that today when I start working on it.
 

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When you have the t-stat housing off, can you reach into the opening and try to move the wp impeller?

There are only a couple of paths it can circulate. Could a pipe be blocked maybe? This diagram may help for flow direction.
97893
81380_coolant-diagram.jpg
 

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Discussion Starter #94
The water pump impeller does not move. I had someone turn over the engine by hand while I had my finger in there and it turned with the shaft. I would be hard pressed to believe it's not turning. But I could be wrong. It's not exactly an OEM part.

According to that diagram, if there is a clog then it would be somewhere between the heater core, the block or the oil cooler. Because I'm still convinced the thermostat isn't opening.
 

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You can test those thermostats yourself. Put them in a pan of water on the stove and bring it close to a boil. See if they start to open at the specified temperature. Either use a garbage pan you don't use for cooking or wash it really really well after.
 

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Discussion Starter #96
You can test those thermostats yourself. Put them in a pan of water on the stove and bring it close to a boil. See if they start to open at the specified temperature. Either use a garbage pan you don't use for cooking or wash it really really well after.
I have tested all 3 (original and 2 new) with a heat gun and they open. Is that not a sufficient test method?
 

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Discussion Starter #97
Did you try to stop the mechanical fan with a gloved hand? If it's faulty, it will stop easily. If it's hard to stop, it's good
It EASILY stopped. Like, one finger lightly scraping the edge of the fan and it stopped dead. What's that mean?
 

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It EASILY stopped. Like, one finger lightly scraping the edge of the fan and it stopped dead. What's that mean?
When the engine is hot, the fan clutch effectively locks up and spins as fast as the pulley. When cold, it should free-wheel with very little effort to stop it on the spinning pulley. Did you do that test on a cold engine or warm?
 

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Discussion Starter #99
When the engine is hot, the fan clutch effectively locks up and spins as fast as the pulley. When cold, it should free-wheel with very little effort to stop it on the spinning pulley. Did you do that test on a cold engine or warm?
Cold. So it's supposed to do that then?
 

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Cold. So it's supposed to do that then?
For the most part, yes. Spin it by hand and notice how much it spins. Then, take a heat gun to the front center of it and then see if it’s harder to spin. That will simulate heat from the radiator


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