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Boiling Coolant? Associated prob

1019 Views 3 Replies 4 Participants Last post by  jaero
I test drove a 2002 GLX 4Motion about an hour ago and when I returned to the dealer (leasing company) I popped the hood and saw the coolant was boiling (vigorously)

Unfortunatley I know very little about engines and planned to bring it to my mechanic for a check-up before considering purchasing it but wanted to check if there is any known issues related to this - or a simple cause.

It didnt seem quite as peppy as another v6 4motion I drove in the past and the upswitch (from overdrive to 5th gear) after passing on the highway seemed a bit delayed (after I let off the gas)

any tips appreciated
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V6 Passats have a pump that circulates the coolant for a while after the hot engine has been turned off.

You sure you didn't mistake the pump moving the coolant in the bottle (which is very visible) for boiling?

As for the shifting, that is probably fine.
VR6's and 30V V6's have the pump. I noticed this in my brother's GLX last year and posted it on VWvortex:
The cooling system is sealed. So as coolant temperature and vapor pressure increases the internal pressure of the cooling system increases. This keeps all the liquid as liquid, i.e. no boiling occurs.

If what you observed really was boiling it would mean that the system had to have a leak somewhere. You would have observed dripping pink liquid or a vapor mist, as well as the odor of the coolant.
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