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Martin
Martin, auto electrical
Category: VW
Satisfied Customers: 731
Experience:  South African Trade Diploma in Auto Electrical
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I have a 2004 passat 1.8. It has been overheating. The rear

Customer Question

I have a 2004 passat 1.8. It has been overheating. The rear flange was cracked. I replaced it along with temp sensor, o rings, and thermostat. I have bleed the system, and it still starts climbing over 190 after a few miles. I ordered a new thermal fan switch since the aux fan is not coming on when it should, but does when I turn the ac on. The lower radiator hose is not hot when it gets over temp. I can't believe the thermostat could be installed backwards? I don't think it would assemble. I need a new direction to look in.
JA: Have you checked the connectors on the sensor itself? It's important that they not be loose or corroded.
Customer: The lower one I have not removed yet. It s
JA: Are you fixing your Passat yourself? What have you tried so far?
Customer: The thermal switch will not be here until tomorrow. I listed all of my steps in the previous text. I have a check engine light for boost pressure sensor only. Nothing with the cooling system.
JA: Anything else you want the mechanic to know before I connect you?
Customer: After it gets over temp it sounds like air gurgling through the engine.
Submitted: 3 months ago.
Category: VW
Expert:  Martin replied 3 months ago.

Hello, Welcome to Just Answer.

When the car is overheat try to ad new coolant it might be that you have not gotten all the air out of the engine. That is the only thing I can think of when I am reading your description. If you are very sure of the fact that you have all the air out of the system you can have it tested for exhaust gas in the coolant at a radiator repair service station. That should give you the best idea as to what to do.

Please if you need more assistance ask before just rating me as I cannot see your car and are only making assumptions from what you tell me.

Greetings,

Martin.

Customer: replied 3 months ago.
There are too many opinions on how to bleed the air. I did it by sliding the heater core bleed hose back with the car running and heat on. I have read it has to be done with the car off??? I have also read there are bleeder bolts along the hard piped coolant lines, but cannot locate any??? I'm not losing any coolant since replacing the bad parts. Idles without overheating, but after 3 or 4 miles temp will climb. I pulled the coolant line off the top of the reservoir, and only have flow when I rev the engine. Thermostat is new, and never opens. Lower hose is never warm. Can you give me a procedure for properly draining and refilling the cooling system? Once again too many opinions. Some say fill through reservoir, and some say pour in through upper radiator hose. I hope this is something you have seen before.
Expert:  Martin replied 3 months ago.

Hi,

I always do the following. Fill the reservoir with coolant until full then with the cap removed, I start the engine let it idle, I then use my hand to squeeze both the radiator hoses in turn to push out the air. The coolant will also come out until the air is mostly out. Let the engine idle until the fan kicks in at around 95 or just over the half way mark on the temp gauge. The termostat should also be open now and both the hoses should be hot. The coolant should also flow in the reservoir. At this point it might suck all the coolant from the reservoir so just ad until full. Then you can close the reservoir and see the the coolant are stable. If it is, switch the engine off let it cool down and see that the coolant level is correct.

People might have other ways that they do it but this is how I do it and it work very well. There are no air bleeders on this car.

Greetings,

Martin.