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What actions to take when Passat ATQ has been run with the wrong coolant?

1141 Views 5 Replies 4 Participants Last post by  jjpark
Hey guys,

I'm finally finishing up all the needed maintenance on the Passat (full timing belt job, valve cover gaskets, PCV system) and I'm wondering what I can do before filling with G12. The previous owner ran the car with green coolant for who knows how long. Is it enough just to fill the car with distilled water halfway and then drain again? Would a CLR treatment/flush for the heater core be wise? The heat blew plenty hot before I started the work, but there was a faint smell of coolant sometimes, not sure if it's due to a leak in a hose by the rain tray or a pinhole leak inside by the heater core (hope not). Would flushing the heater core prevent any future problems or would the G12 eventually break down whatever gunk might be in there? It is getting cold up here in the northeast, so I'm trying to finish up any auto work in a hurry. If I can avoid extra work I will.

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I'd recommend several fill/drains with distilled water until you are sure all the green coolant is out. G12 mixed with other coolants is more likely to form a gel/sludge than dissolve any gunk left in the system. And as long as you are going to that much work a CLR treatment would not be a bad idea although once again, I'd be sure to flush it out completely before adding the final G12 mix. Last but not least, you need to follow the 'right' procedure to get all the air out of a ATQ coolant system so be sure to read up on that when you are ready to go.
Agree with the others on the flush but you need to fix those leaks 1st.
Agree with the others on the flush but you need to fix those leaks 1st.
It had seemed like the waterpump was leaking when I did the timing belt. Possible to get smells in the cabin from that?
Yes you can get smells into the cabin from something leaking in the engine bay. I would pull the carpet back on the front passenger foot area if you suspect a leak near the heater core. There is a lot of padding under the carpet that will hold and hide any water/coolant and you won't notice it till your CCM is under water and starts creating electrical havoc.
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