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David
David, VW Master Technician
Category: VW
Satisfied Customers: 2360
Experience:  VW Master Technician Certified for 9 years, ASE Master Technician Certified
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Volkswagen Passat GL 04 vw pasant 1.8t no heat new thermostat

Customer Question

04 vw pasant 1.8t no heat
new thermostat water pump t belt and related parts.
lower radiator not as hot as the rest.
low flow to heater core.
thanks for youre help
Submitted: 3 years ago.
Category: VW
Expert:  David replied 3 years ago.
Due to the location of the heater core, higher than most of the engine, the core will tend to get plugged. This is a very common issue with the Passat and the Audi A4. The only repair is to replace the heater core. You can try to flush it out, but I have had very little success with this. The heater core will plug up and cause a very slow coolant flow through the core. Sorry to say but you will need to replace the core.
Customer: replied 3 years ago.
why is the lower rad hose cold
Expert:  David replied 3 years ago.

Because that is the cooled water hose. Water only flows through the lower hose once the thermostat has opened. If the thermostat is closed there is no or limited flow through the radiator. If the outside temp is cold it may take a while to be able to heat up the water in the radiator to be able to notice it in the lower hose.

 

The hot water flows from the upper hose into the radiator and then it is cooled, the lower hose normally will not show heat until the car has been run for a while or under a load.

Customer: replied 3 years ago.
ran for over 2 hours still not warm
Expert:  David replied 3 years ago.
two hours at idel, under load also what is the outside temp
Customer: replied 3 years ago.
inside garage idle and at 2000 rpm
Expert:  David replied 3 years ago.

The best way to see water circulation is to use a laser thermometer. This you can point at the radiator and follow the temp of the coolant. I dont think you have an issue with the thermostat or the water pump. Running the car that long it would overheat if there was an issue with the water pump and or thermostat. The aluminum radiators in these cars are very efficient, so without knowing the ambient temp its hard to determine why the lower hose is cold, other then the radiator is efficient and cooling the coolant going through it

 

I have seen many of these at the dealer were the coolant flow is very restricted on the heater core.

 

You can also use a scanner to see what the coolant temp is in the block, but that normally requires a factory type scanner or the Ross-Tech program.

Customer: replied 3 years ago.
have scan tool reading 217 deg after therm replacement was 168 before
does this motor have a secondary coolant pump.
does the turbo help with coolant flow?
Expert:  David replied 3 years ago.

That temp is higher than what it should be. The turbo does not help with the coolant flow and there is no additional water pump that works with the car running. The only item that works is the water pump driven off the timing belt. Did you use a factory thermostat or after market. Also did you vacuum fill the car or just fill the coolant tank.

 

This car if equipped with an after run pump, only circulates a small amount of coolant after the car is shut down. The after run pump do not work when the car is running. Not all are equipped with this feature.

Customer: replied 3 years ago.
coolant tank.bleed it of at heater core through hose as per directions
start car nothing
no thing coming ot of bleed hole with car runninghold coolant tank up pleanty of coolant out of blead hole
Expert:  David replied 3 years ago.
Normally to bleed the car out of the bleeder at the hose, you need to have the coolant bottle cap on, and allow the car to start to warm up, this will cause a slight amount of pressure and force out any air in the block. These cars can be a pain to burp all the air out at times. May be part of your problem if it has air in the block. At the dealer we vacuum fill them to prevent any air issues
David, VW Master Technician
Category: VW
Satisfied Customers: 2360
Experience: VW Master Technician Certified for 9 years, ASE Master Technician Certified
David and 3 other VW Specialists are ready to help you
Customer: replied 3 years ago.
thank you for youre help
if u think of something i am missing let me know
will pay u for your time
drew

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