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My new to me B5 Passat 1.8t is having some issues.
The first drive of the morning the car takes FOREVER to reach the 190° mark on the coolant temp gauge. After it reaches that point it’ll stay there for a few minutes and then start dropping back down. The heat also blows “warm” but not by any means as warm as it should.
Am I right in thinking this is caused by a bad thermostat? Here’s where the temp will usually drop, and sit for on the remainder of my drive but occasionally will drop all the way down into the “3 bars” area..
98337
 

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Yep, I bought a used A4 years ago, and it did the exact thing until the 'stat was replaced. The good news is that the thermostat on the 1.8T is simple to change, compared to the 2.8, which is behind the timing belt. Get that changed sooner than later, as your car will not run in the efficient closed-loop mode while the coolant is too cold.
 

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Yep, I bought a used A4 years ago, and it did the exact thing until the 'stat was replaced. The good news is that the thermostat on the 1.8T is simple to change, compared to the 2.8, which is behind the timing belt. Get that changed sooner than later, as your car will not run in the efficient closed-loop mode while the coolant is too cold.
Yup,
Yep, I bought a used A4 years ago, and it did the exact thing until the 'stat was replaced. The good news is that the thermostat on the 1.8T is simple to change, compared to the 2.8, which is behind the timing belt. Get that changed sooner than later, as your car will not run in the efficient closed-loop mode while the coolant is too cold.
Yup! I figured as much. Just went ahead and ordered a new thermostat, housing, temp sensor, and coolant.
Going to replace the thermostat, sensor and do a coolant flush. The procedure for the 1.8t looks incredibly easy. Going to tackle it this weekend. Lucky for me, the car isn’t my daily driver so it can sit in the garage until it’s time to work on it!
 

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Just be aware that the engine should not be running while bleeding the air from the cooling system. The heater hose nearest the battery has a small hole punched in it, normally over the heater core pipe. This hole is used to vent out air after the hose is un-clamped, and pulled away from the firewall until the hole is past the end of the pipe. The reservoir is also lifted as high as its hoses allow. With the reservoir filled and filler cap removed, the heater hose is left in the vent position until a small steady stream of coolant emerges from the vent hole. The hose is then pushed back into position, clamped, and the reservoir reattached.
 
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