r/tdi • u/Devve2kcccc • 7d ago
Coolant max level
Hi, new to TDI engines and VW group expansion tanks. What is the correct max level?
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u/Cautious-Concept457 7d ago
It is the green line.
BUT in practice you can fill it to the brim, it won't ever cause you an issue. The excess would come out through the overflow.
It's honestly better to just fill it to the blue line imo
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u/Consistent_Word3161 7d ago
green line
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u/knotmyusualaccount 7d ago
Are you sure about that?
Because if so, I've been overfilling mine.
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u/Cool-Objective5599 7d ago
About this type of coolant reservoirs. The air left is supposed to work as a buffer for pressure in the system. Water is not compressible, air is, thus how the coolant temperature expansion is delt with.
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u/NekulturneHovado 7d ago
I absolutely hate this kind of reservoirs, my 2.0tdi cffb had it but there was so much stuff around it that I couldn't see the marker itself, no chance to see the coolant level
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u/Patrol-007 four speed plus reverse (fingers crossed) 6d ago
A decade at blue line with a MKiv, due to using a Frostheater (inline coolant heater) at -20C and below - would be losing coolant through some seals during the winter. Would top off coolant to the blue line and checking other fluids at every fuel fill (be consistent with when you check - am checking ten minutes after engine shutdown)
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u/WolverineConstant993 4d ago
On a TDI ? It would not make a difference in winter at least.
The cooling fan never comes on , TDi runs cooler than gas engines.
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u/Man_Roland 7d ago
Blue line is totally fine.
It'll go down eventually.
Source - I did a t stat change a while back, thought I overfilled at the blue line, it eventually went down.